Building science

2.6.1 Surface resistances in m2K V

Building science

Joachim Achtziger

Thermal insulation

The thermal insulation of a building is intendedto contribute towards a hygienic and comfort-able internal climate, which is not detrimentalto the heaith of the occupants and users of thebuilding, and at the same time protects thestructure against the climate-related effects ofmoisture and their consequences. The energyrequired for heating in the winter and measuresto provide an acceptable internal climate in thesummer without the use of air conditioning forcooling must be optimized in conjunction withthe necessary thermal insuiation and energy-saving measures. These days, thermal insula-tion to a building is not just a means of savingenergy but an important element in an environ-mental protection programme. Therefore,reducing emissions of pollutants from buildingheating systems is an important aspect.Besides saving heating costs for the user, anincreasingly important factor, ever more pre-cious energy and fuel resources are alsospared.The Construction Products Directive [13], themost important element in the creation of aEuropean Single Market for the constructionindustry, acknowledges the importance ofthermal insulation and defines the area of"Energy economy and heat retention" as oneof six essential requirements. On the whole,the costs and adaptation problems of Euro-pean standardization are outweighed by thebenefits, The effects of these are to:. harmonize the markets,. create uniform framework conditions withinthe EU,

' attain European supply conditions,' set uniform evaluation and testing standards,. set uniform standards of quality recognizedthroughout Europe; different standards in dif-ferent countries can be assessed accordingto a system of graded performance classes.

The objective of the principal document "Ener-gy economy and heat retention" is, taking intoaccount the location, to keep down the con-sumption of energy related to the use of abuilding and its technical systems, and toguarantee an adequate of standard of thermalcomfort for the occupants, This encompassesand standardizes the following main factors:

. location, orientation and form of the structure,

. physical properties of materials and compo-nents used for the structure,

' the design of systems for the technical ser-vices,

. performance features for the components ofthese systems, and

. the behaviour of the users of the building.

The combination of planning and design stan-dards, standards with generally acknowledgeddesign data, standards for the measurement ofcomponents and materials as well as thosecovering products is shown in a very muchsimplif ied and generalized form infig.2.6.2.The quality of a building in energy terms iscalculated according to a design standard.Further rules are necessary for assessing thethermal performance of parts of a building,such as rooms adjacent the soil, rooms in theroof space or parts of the building with lower'temperatures, as well as standards for specify-ing the thermal performance of componentsand their non-constant behaviour upon heatingand cooling. Tables of values or measurementsof components prepared according to estab-lished rules serve for the calculation of trans-mission heat losses from a building envelopeand given heat gains. Fufther, components canbe assessed according to their constituents,based on the properties of the materialsemployed. Therefore, a complete, coordinatedstandardized concept from the product proper-ties to final energy requirement is available fordescribing the performance of a building. InGermany, DIN 4108 remains as the NationalApplication Document and the publicationdescribing national requirements. The firstnational measures for saving energy in theheating of buildings were established withinthe scope ofthe Energy-savings Act of 1976,which led to the 1977 Thermal Insulation Actand its subsequent revisions in '1982 and 1995.The new Energy-savings Act of 2001 has thepotential to achieve a further 30% saving inenergy in the heating of buildings. A completeenergy planning concept is available for thedesign of buildings, taking into account heat-ing systems and an assessment of the energycarrier.

Direction of heat flowHorizontal Downwards

R" 0 .10 0 .13 0 .17

0,04R

160

d

Thermal insulation

Heat transfer, thermal insulation parameters, terms

Heat transfer can take olace in the form of con-duction in solid, l iquid and gaseous media,and in the form of radiation in transparentmaterials and vacuum. In building materials,heattransfer is expressed by the property ofthermal con d uctivity. Thermal cond uctivity l.specifies the heat flow in W passing through1 m2 of a 1 m thick layer in t h when the tem-perature gradient in the direction of the heatflow is 1 K. The lower the thermal conductivity,the better is the thermal insulation for a giventhickness of material. The thermal insulationcapacity of a component is characterized byIhe thermal resistance R, lt is determined bydividing the thickness of the layer concerned(in m) by the material's thermal conductivity l.(in WmK). Multi-layer components require thevalue of each layer to be calculated separatelyaccording to this method. The total of the indi-vidual values gives the thermal resistance Rfor the complete component. The higher thethermal resistance, the better is the thermalinsulation.To determine the thermal transmittancethrough a component, we also need to knowthe internal and external surtace resisfance R",and R"". Thesurface resistance is the resis-tance of the boundary layer of air to the trans-fer of heat from the internal air to the compo-nent and from this to the external.air. The sur-face resistances are generally standardizedaccording to the orientation of the component(vertical, horizontal) and the external air circu-lation (unrestricted, ventilated, not ventilated)as given in table 2,6.1. They have been deter-mined for a degree of emissions from the sur-face of e = 0.9 and a wind soeed n = 4 m/s atthe external surface. The total of all resistances- those of the layers of the component and thesurface resistances of the boundary layers ofair - is the total thermal resistance R- which thecomplete component applies to resist the flowof heat. The reciprocal of this value is the ther-mal transmittance U - the characteristic vari-able for the thermal insulation of a buildingcomponent. The U-value is fundamental forcalculating the heating requirement of a build-ing. The smaller the U-value, the better is thethermal insulation. The calculation of the ther-mal resistance of single- and multi-layer com-oonents as well as the U-value is shownschematically in 2.6.3, The calculation of the U-value for comoonents made Jrom severalneighbouring sections with different thermalconductivities is dealt with in the section enti-tled "Thermal bridges". The mathematicalassessment of heat transfer and temperaturegradients in components is a relatively difficultproblem depending on time and geometry.Therefore, to simplify the work we assume sta-tionary, i.e. constant, temperatures on bothsides of the component as well as a one-dimensional heat flow across the thickness of

2.6.2 Diagram of relationship between materials, components and design standards for assessing buildings in terms

of energy performance

2.6.3 Calculation of thermal resistance and thermal transmittance values for single- and multi-layer masonry

components

Tabular valueslvlethods of calculation

Methods of measurement

Fabricatedon slte

-,,\\-/

\ , / \

Construction Sketch of principle Equation

Thermal resistance

Sin gle-layer component _ o, 'R

Thermal resistance

lvlulti-layer componenl

1 1

] 0 , d 2

1

2,/,42o"l

1'!Rn

- d r d 2n = - + - +

ln', rnz

Thermal transmittance

Single- or multi-layercomponent

$ i

r61

Building science

Expanded clay concrete

30o/o

2Oot

1 "6n-,-''

u

;al

!coa

6EocF

2.6.4 Thermal conductivity of dry expanded clay and expanded shale concrete samples with and without variousquartz sand additions by volume of total aggregate content (%) in relation to gross density (average tempera-ture 10"C), after W. SchLlle, Giesecke and Reichardt [195]

Expanded shale concrete

the component. This approach is generally suf-ficiently adequate for winter conditions withpermanently heated interiors and constant lowtemperatures outside, as well as for calculatinga mean heat loss over a longer period of t ime.At equil ibrium, the heat f low

< D = U x A ( O i - O " )

passes through an external component with anarea A on one side of which there is internal airat a temperature Oi and on the other, there isexternal air at a temperature 8e. Therefore, thethermal transmittance U is critical for the trans-mission heat loss through the component.However, the graphic representation of the U-value in fig. 2.6.8 reveals that only slightimprovements are possible beyond a certainthickness of component. This non-linear be-haviour leads to the situation of increasingcosis for more and more insulation having eversmaller energy-saving effects. The variables,symbols and units necessary for assessing thethermal performance of the building envelopeare given in table 2.6.6. Further details are con-tained in DIN EN ISO 7345 and the respectiveDarts of DIN 4108.

Thermal conductivity of building materials

With the exception of very dense stone, build-ing materials are porous to some extent. Theycontain air-f i l led voids of various sizes in vari-ous arrangements, and these can have a sig-nificant effect on the transfer of heat. The ther-mal conductivity of masonry depends on:. the thermal conductivity of the solid con-

stituents,. the porosity or gross/bulk density,. the nature, size and arrangement of the

pores,' the radiation properties of the boundary walls

of the voids,'temperature, and. the water or moisture content.

As the thermal conductivity of the materialunder observation depends on the temperaturewithin its range of application, for building pur-poses all thermal conductivity values are relat-ed to a mean temperature of 10"C so thatuneouivocal comparisons can be made. Forthe same reason, material parameters arespecified for the dry state of the material, initial-ly without taking into account the fact thatmoisture increases the thermal conductivity.Table 2.6,5 provides an overview of the orderof magnitude of the thermal conductivities ofsolid materials used to manufacture buildingand thermal insulation materials. Materials withmainly crystall ine components exhibit a higherthermal conductivity than those with vitreous orlime-based components. For instance, theaddition of quartz sand to concrete or mortarhas a noticeably detrimental effect on the ther-mal conductivity. Measurements of concrete

0,90

0,80

0.70

0.60

0,50

0.40

0.90

0,80

o.70

0.60

0.50

0.40

30o/o 1

209i.--/u Vo

'{.

0.301 000 1100 1200 1300 1400 1500 1600 1700

Bulk density (kg/m3)

2.6.5 Order of magnitude of thermal conductivity(WmK) of solid constituents of building and ther-mal insulation materials, after J.S. Cammerer [29]

I norganic building lra!glq!sCrystalline

perpendicular to crystal axisparallel to crystal axis

QuaftziteLimestone, marble, graniteBasalt, feldspar, sandstoneAmorphous solidified mells such asblast furnace s]-ag and glasses 0.7 Io 1.2Natural orqaniCsubstances 0.3 to 0.4

0.16 to 0,35

2.6.7 Thermal conductivity of building materials

0.301200 1300 1400 1500

2.6,6 Variables. svmbols and units used in thermalperformance__ _

Phvsical variable Svmbol Unit

4.7 Io 7.Oto 14

61 .6 t o 4 ,0

"cW/mKm'?K,AiVm2K.AiVm,KAV

m2K,\NWlmzK

W/m2J,4<gKkg/m3mm2m3kg

TemperatureThermal conductivityThermal resistanceI nternal surface resistanceExternal surface resistanceTotal thermal resistance

(airto-air resistance)Thermal transmittanceHeat flowHeat flow rateSpecific heat capacityGross/bulk densityThicknessAreaVolumelvlass

o7,RR' - sR

R

;q

cp

d

m

0 5

0.4

0.2

<>css

Ol

cCoa5 o.o3Eo

gF

1 , 0

0 .1

0.3

162

Thermal insulation

with different quartz contents are shown in fig.2.6.4. Generally speaking, the use of aggre-gates coniaining quartz can be assumed toreduce the insulating effect of the concrete by20%. However, the characteristic variable influ-encing the thermal conductivity of building andinsulation materials is the gross density. Thisrelationship is shown in Iig. 2.6,7 - the eval-uation of more than 1000 measurements in aEuropean research project. After being incor-porated into a structure, especially in externalcomponents, building materials exhibit agreater or lesser water content. Owing to thegenerally relatively small proportion, this isknown as moisture content. Depending on theporous structure and the magnitude of themoisture content, the water may parily or com-pletely fi l l larger and smaller pores or justadhere to the sides of the oores or in cornersof the pores. Damp building materials exhibit ahigher thermal conductivity compared to thedry state, and this depends on the moisturecontent, which in turn is related to the type ofmaterial.Figure 2.6.9 shows the thermal conductivity ofvarious building materials as a function of themoisture content; this can be expressed relat-ed to either the volume or the mass. lf the ther-mal conductivity in the dry state and the mois-ture content of the building material is known,the thermal conductivity in the moist state canbe calculated according to DIN EN ISO 10456using the equation

lu,*= 1,.,0,u x F,

tr _ afu(u2, u1)' m - "

t r _6 f , {V2-v j )' m - '

where:fu and f, = conversion factor for mass- andvolume-related moisture content respectivelyu, and f, = moisture content 0 of dry materialu, and ry, = mass- and volume-related mois-ture content respectively.

The moisture contents u and y common inpractice, as well as conversion factors for themoisture content, are given in DIN EN'12524corresponding to table 2.6.10. The standard-ized moisture contents u (mass-related) and y(volume-related) are related to the moisturecontent equilibrium of the corresponding mate-rial at 23'C and 5Oo/o relative humidity, or 23'Cand 80% relative humidity. The moisture con-tents in the desired reference ambient condi-tions and the conversion factors for the influ-ence of the moisture content on the thermalconductivity can also be determined individual-ly for certain materials by way of experiment,with the aim of achieving more favourable ther-mal conductivity values for real situations. Theterm "nominal value" was introduced to achievea uniform specification for the properties of

building materials being marketed internation-ally. The nominal value for thermal conductivityis the value to be expected for the thermalinsulation property of a building material orproduct, assessed by way of measurementstaken at a reference temperature and humidityaccording to table 2.6.1 1, specified for definedpercentiles and confidence ranges and corre-sponding to an expected service l ife undernormal conditions. The term "service life" alsoincludes the ageing behaviour of products,such as thermal insulation materials with high-molecular prooellants, which over time under-go an exchange of gas with the surroundingair, or the settlement behaviour of loose ther-mal insulation materials in voids, Only thematerial scatter and the influence of moistureare relevant for masonry products.fhe design value for thermal conductivity isthe value of a thermal property of a bulldingmaterial or oroduct under certain external andinternal conditions, which can be regarded astypical behaviour of the material or product inits form as a constituent of a component. Thedesign values are determined by the user/planner, building authorit ies or national stan-dards corresponding to the intended applica-tion of the product, the environmental or clim-atic conditions as well as the purpose of thecalculat ion, e.g. :

. energy consumptron

. design of heating and cooling plants' surface temperature. compliance with national building codes. investigations of non-constant thermal

condi t ions in bui ld ings

Thermal insulation design values can bederived from the nominal values by means ofthe conversion factors given in DIN EN ISO10456. This is customary for thermal insulationmaterials. Design values for masonry materialsare derived from the thermal conductivity in thedry state.

Thermal insulation provided by layers of air

Layers of air in components transfer heat byconduction, convection and radiation.The various heat transport mechanisms havethe effect that, unlike with solid materials, for airthe thermal resistance R does not rise withincreasing thickness but instead reaches amaximum value and then remains constant.Thermal resistances of layers of air accordingtotable 2.6J2are speci f ied in DIN EN ISO6946 and may be taken lnto account only whenanalysing thermal performance if they are iso-lated from the outside air. Such layers of airalso include the cavities in twin-leaf masonrywalls to DIN '1053 because the openings in theouter leaf are too small to bring about anexchange of air with the outside air. The extentto which a layer of air with small openings tothe outside air can sti l l be regarded as a

2,6.8 Thermal transmittance U in relation tothermalresistance R

U (WmzK)

2.38

1 .491 .O7

oasffi2.0 3.0 4.0

R (m2Kl,{)

2.6.9 Thermal conductivity of building materials inrelation to moisture content (volume- and mass-related)- Y6lurns-lsl3tsl- - - - - mass-related

Thermal conductivity (W/mK)

,-/

. - t - '

-' clay brP = t c r

1 '= 43

rcKs!6 kg/m 3

o/o

-- ' ---z' - - Punlce concrele

1015 kg lm '

58 lo

Gas concret(

P = 540 kg/n

N = 7 9 o / o----:==

Perlite

??/evtl. aerated cr 3

---/.a - : - - - - -

= 303 ko/m 3

)2

N = 8 7 o / o

=-==:=-

4 6

lvloisture content (%)

6

5

4

3

2

0,5

0,4

0,1

163

Building science

2.6.10 Moisture-related propedies of masonry materials

l\.4aterial

Solid bricks

Calc ium si l icatePumice concreteNormal-weiqht concrete

concrete

Concrete with pre-dominantly expanded

with blast-furnace

concreteConcrete with other

Mortar (masonry moftar 250-2000

?44 Bg1glglggconditions accorqing to DIN EN ISO 10456Property Boundary condition

| (10 "c) _ i l (23.C)a b c d

Referencetemperature 10'C 1 0 ' c"23,50aqed

stationary layer, or to which insulating valuespoorly or well ventilated layers of air can begiven are shown schemat ica l ly in f i9 .2.6.13.Small or divided air spaces corresponding totig.2.6.14, as occur in perforated masonryunits, horizontally perforated clay bricks andgrip aids, require special consideration. Inthese cases, the geometry of the perforations -the gap width{o-thickness ratio - has an influ-ence on the equivalent thermal conductivity ofthe void, The thermal resistances of air spaceswith any dimensions can be calculated accord-ing to DIN EN ISO 6946, The thermal resis-tance of an air cell is found usinq the eouation:

a -(hu+ 1/2 Eh,o (1 +d2lb2 - d/b))

where:Rs = thermal resistance of air spaced = thickness of air space

udry is a low moisture content attained after drying,u23,50 is a moisture content which becomes established in equilibrium at 23'C air temperature and 50%relative humrdity.

2.6.12 fhermal resistance R of stationary air layers - surJaces with high degree of glE!lg!!@ono fhea t f bwry]m __-. R in mrK,A/V

Horizontal

= width of air space= degree of exchange through radiation

hro = €xternal surface resistance due toradiation for a black bodv

hu is as follows:. for a horizontal heat flow:

h" = 1.25 Wm2K or 0.025/dW/m2K,whichever is the greater

. for an upward heat flow.hu = 1 .95 \N/m2K or 0.025/dW/m2K,whichever is the greater

' for a downward heat flow:hu = 0. 1 2d 0 44 W/m2K or O.025/d W/m2K,whichever is the greater

where d = thickness of air space in direction ofheat flow.

The thermal optimization of perforated masonryunits depends on the distribution of perfora-tions and their cross-section, In comparing dif-ferent patterns of perforations, the proportion ofperforations and the thermal conductivity of thesolid material must be kept constant. Figure2.6.1 5 i l lustrates the thermal insulation qualit iesfor various arrangements of perforations in claybricks with 40% perforations [46]. The 1B sam-ples are arranged in order of descending ther-mal conductivity.ln l ightweight concrete units the thermal con-ductivity - for the same gross density -depends quite crucially on the proportlon ofperforations and the arrangement of cells.Figure 2.6.16 shows thermal conductivit ies ofmasonry made from three- and four-cellhollow blocks, as well as a slotted unit calcul-ated according to EN 1745 assuming a grossdensity of 600 kg/ms. The values given apply tounits made from expanded clay concrete andlightweight mortar LM 36,

E

Moisture u23"C

,3zo2 3 ' C

aqedA;.1.; - "U6o

, upwaros0,000 . 1 10 .130 . 1 50 . 1 60 . 1 60 , 1 60 , 1 60 , 1 6

Downwards0571 0t c

2550100300

0.000 . 1 10 . 1 30 . 1 5o . 1 70 . 1 80 . 1 80 . 1 80 . 1 8

0.000 . 1 10..130 .150 . 1 70 , . 19o .21o.22o.23

Moisture content al23"C,50% re

Moisture content at23'C, \Oa/a rn

q!q.p]419l!!s!]}9r)

NC!9.l4q!qdiq1g trel!9lllqy Q_e4!Cl!gq Qy lllgelinterpoiation.

2.6.13 Thermal resistances of stationary, poorly ventilated and well ventilated air layers according to DIN EN ISO 6946

Opening <500mm2 per 1 m length

Stationary air layer

Opening > 500 mm2 per ' l m length< ]500 mm2 per 1 m length

Poorly ventilated air layerR - half the value of the stationary air

layer but max.0.15 m2K,4V

Opening > 1500 mm2 per 1 m length

Well ventilated air layer

R"" = R"i = 0.13 m,l(W

164

Thermal insulation

Determination of design values for thermal

conductivity

The design value for thermal conductivity foruse in calculating the thermal insulation ofbuildings is defined for Germany on the basisof the practical moisture content or the mois-ture content equil ibrium aI23"C and B0% rela-tive humidity. To do this, the practical moisturecontent or the reference moisture content ofthe building material must be known. Practicalmoisture content is understood to be a quantityof water in the building material whichbecomes established in an adequately drystructure over the course of time. This iscaused by water being absorbed from the air(hygroscopicity) and the formation of conden-sation on surfaces and within components.Therefore, practical moisture content excludesmoisture due to building processes which hasnot yet fully disappeared and saturation result-ing from precipitation, rising damp and dam-age to the building. The practical moisture con-tent is defined by the relative cumulative fre-quency of a multitude of investigations on asmany structures as possible. Figure 2.6.17shows the typical progression for a buildingmaterial. The results of measurements of auto-claved aerated concrete walls and roofs (seefig.2.6.21) can serve as an example for thedrying gradient of external components [104].External walls with adequate rain protectionand permitting evaporation on both sides dryout faster, The drying period lasts about twoyears under different conditions. As the dryinggradient is considerably influenced by theweather, the occupation of the building, thestandard of construction and the orientation ofthe walls, and determining the moisture byremoving cores of material is expensive andcomplicated, a new method of determining themoisture characteristic of a building materialby way of its hygroscopic moisture contentequil ibrium in a defined climate is now beingused (fig. 2.6.18). Moisture absorption at 23'Cand B0% relative humidity has proved equiva-lent to the field investigations. We speak thenof the reference moisture content, a parameterwhich has also become established in Euro-pean standards (see table 2.6.10, columns 5and 6). The water content of a building materialis specified either as the quantiiy of water con-tained in a mass unit of the material, related tothe dry mass as the "mass-related water con-tent" u in kg,&g, or as the volume of water con-tained in a volumeunit of the material, related to the materialvolume as the "volume-related water content"y in m3/m3.The mass-related moisture content is recom-mended for building materials because itremains constant over the entire gross densityrange. As an example, f igure 2,6. 19 shows theresults of tests to measure the sorptive mois-ture of aerated concrete at an ambient temper-ature of 23'C and B0% relative humiditv, and

2.6. l4 Smal l or d iv ided non-vent i lated voids {a i r spaces)

d.

-1--

Heat flow

2.6,15 Variations in clay brick cross-sections for a constant proportion of perforations and constant total web thick-ness (heat flow horizontal) [2]

t'tt b /"7- ."

Delta Rectangles, par-perforations allel + grip holes

Diamonds,offset

Circularholes, El l ipses,parallel parallel

Hexagons,offset

El l ipses,offset

Rectangles,paral le l

T-bricks Interrupted outerweos

Rectangles, ofl- Rectangles, oflset + grip holes seY"standard"

tilmll l L j IL lu l

t!l!_[]lC

Gothicbricks

Meanderbricks

"Spr ing"bricks

Fine ceramic "B"bricks

Fencebricks

ffiffiWWWW2,6.16 The influence of pedorations on the thermal conductivity of lightweight concrete units with

gross density 600 kg/ms

Unit Proportion of Concrete Thermal conductivityperforations gross density of masonry

kq/m3929923680

3535B

c

0,270.250.18

WWWffiffiffiWWWWffiffiK-bricks

Building science

20

EEp 1 6cooo

zoEr r 8a6I6 4Elb

3 a no -fo

o.F

6

bcr

2.6.17 Cumulative frequency of moisture contenlof pumice building materials in externalwalls determined in 88 samples

Volume-related moisture content

2.6.19 Sorbed moisture (equilibrium moisture content)of autoclaved aerated concrete at 20'C and 80%rh in relation to the volume (y) or the mass (u) ofthe material depending on gross density

0300 400 500 600 700 800 900

Moisture content (%)

2.6.21 Drying-out of autoclaved aerated concrete exter-nal components (walls and flat roofs) plottedagainst time [3]

0 2 4 6 8

Time (years)

The initial progression of the given range stems frommeasurements on external walls at the Fraunhofer Insti-tute's open-air site (lower limit: external wall, evaporationpossible on both sides; upper limit: outer face sealed,evaporation only possible via inner face).o external wallso flat roofsrepresent measurements of actual buildings.

166

2.6.18 Volume-related moisture content in relation torelative humidity for absorption and desorptionof a calcium silicate unit with gross density1720kg/m3, after Kunzel

' Abiorptiono Desorption

I//

4 _-----tI

Relative humidity (%)

2.6.20 Percentage increase in thermal conductivity olautoclaved aerated concrete depending on1.,0,,,, in relation to % by vol. or 1 mass 70, afterl6 l

o\ o

B -:-\r>Q.

o

at o

0 .08 0 .10 0 .12 0 .14 0 .16 0 .18 0 .20

Thermal conductivity (W/mK)

2,6.22 Ventilated natural stone facades and lightweightcurtain walls; increase in thermal transmittanceof wall in relation to number of fixings and fixingmaterial

AU (WmzK)

0 1 2 3 4

No. of fixings per m2Natural stone facade

o Lightweight curtain wall

t ig. 2.6.20 shows the relationship between ther-mal conductivity and moisture content derivedfrom this. Taking the mass-related moisturecontent as our reference ooint allows the use ofa surcharge to cover the influence of the mois-ture on the thermal conductivity, which is inde-pendent of the material bulk density and thethermal conductivity. To carry out a thermalinsulation analysis, the user requires a thermalconductivity design value for the particulartype of masonry construction. This takesaccount of the type, form and gross density ofthe masonry unit as well as the type of mortar.The thermal insulation properties of differenttypes of masonry can be determined fromtables according to EN 1745 or by measuringsamples of wall or by calculation based on thematerial parameters [3]. To take into accountthe influence of moisture on the thermal con-ductivity, the reference moisture contents andmoisture correction values Fm given in table2.6.23 apply in Germany. More favourablevalues not contained in the table mav beverif ied experimentally.

Thermal performance of external walls

The thermal resistance R of single-leaf plas-tered external walls, single-leaf external wallswith internal or external thermal insulation, ortwin-leaf walls with or without additional insula-tion is calculated by simply adding togetherthe R-values of the individual layers. As anexample, f igure 2.6.24 shows a plasteredsingle-leaf wall with a thermal insulation com-posite system. lf the insulation is attached withmechanical f ixings, additional heat lossesoccur depending on the type of f ixing, Basedon experiments and numerical pararneterstudies [6, 205], the heat transfer for a com-ponent (including the thermal bridge effect)can be represented in a simplif ied estimationmethod as follows:. by adding the increase AU to the thermaltransmittance value U for the undisturbedsectton

U " = U + a u

. by a percentage increase in the thermaltransmittance value U

U" = U(t+-rOO)

. by adding the increase in the conductance ofa component by means of the discrete ther-mal transmittance 1

L = I U i A , + L 1 ,

The first method with a surcharge AU was firstused in the European standard EN 6946. Thecorrection values given in table 2.6.25 apply tothe various types of anchors used for fixingthermal insulation composite systems. A ma-sonry substrate behaves slightly better than a

1 4

1 0

I

s6;9

A

o

6 ?

ac ^

1 0

c

o

co

!=lm

o 4

E

> 1 '! -

coOA jl6'6

Thermal insulation

lvloisture contents and conversion factors for moisture content according to draft standard EN 1 2524 table 2,

and moisture correction factor F- according to draft standard EN 10456

lvlaterial Moisture content at23 "C. 80% rh

kgkg

Conversion factor formoisture content

MoisturecorrectionfactorF-

Autoclaved aeratedconcreleLighh//eight concretewith pumiceLightweight concretewith expanded clayClayCalc ium si l icatelvlortar

0.03

4

1 01 04

1 . 1 31 . 2 71 . 2 7

1 . 2

1 . 1 5

1.08

o.o120.o240.06

concrete one. The type of rendering has practi-cally no influence on the outcome. The thermalconductivity of the insulation material and itsthickness have no effect on the additional heatloss when adding AU. The AU-values given peranchor can be simply added together for theparticular application, slnce in the most un-favourable situation the anchor only has aneffect within a radius of max. 250 mm about itsaxis. Influences of AU < 0.002 can be ignoredbecause the additional heat loss l ies below3o/o.

At just 1% the influence of the thermal bridgescan be neglected for mechanical f ixing sys-tems using plastic rails. However, if the plasticrails are replaced by aluminium ones, thisresults in a considerable surcharge of AU =0,05 Wm'?K for horizontal rails fixed to the load-bearing substrate at 500 mm centres.In the case of a thermally insulated wall with aventilated external cladding made from anyone of a number of different materials, thecladding fixings in the wall act as thermalbridges. Their effect depends on the followinginfluences:. material of the fixings' number of f ixings per unit surface area. type of wall material.Timber supporting constructions with verticaland horizontal battens for carrying the thermalinsulation and the cladding have only a rela-tively small effect on the heat transfer. The ther-mal insulation of such constructions can becalculated according to DIN EN ISO 6946. Oneparticularly unfavourable case with a high num-ber of f ixings is the ventilated facade with acladding of natural stone. The natural stoneslabs are usually f ixed to the wall by means ofsupporting and retaining anchors. Theabsolute increase in the thermal transmittancecaused by the anchors does not depend onthe thickness of the insulation and the type ofstone basically has no influence on the heattransfer. On the other hand, replacing a con-crete loadbearing wall with one of masonryreduces the influence of the anchors by 4Oo/o.There is a l inear correlation between theabsolute increase in the heat transfer and thenumber of anchors per unit surface area (seefiq.2.6,22). The influence of the thermalbridges is cut by half when stainless steelanchors are used. lf the natural stone facade isreplaced by a l ightweight venti lated claddingwith other types of fixing to the loadbearingwall, surprisingly, the influence of the anchorsremains the same. The use of a olastic underlay ("Thermostop") between bracket andmasonry brings about a clear reduction in thethermal bridge effect, but a thermal breakattached to the cold side of the bracket hardlvhas any effect.An important planning instrument these days isthe "Determination of the thermal influences ofthermal bridges for curtain wall venti latedfacades" [163]. The discrete thermal bridge

2,6.24 Example of calculation for external wall of plastered single-leaf masonry

Layer

Internal plasterCalc ium si l i -cate masonryBondingcompounoRigid ex-panded poly-styrene foamTexturedrendeflnq

Thickness oflayer rn m

Rm2K,i1,{

IRW/mK

6 0 .015

5 0 .175

4 -

3 0 ,120

1 -

0.35

0.99

0.04

0 , 1 8

3.00

Thermal resistance R = X d/)\. = 3.22

Thermal transmittanceU = 1/(0.13 + 3.22 + 0.04) = 0.30 Wm'zK

Type oIanchor

Dia, of anchorsmm

aK per ancnorW/m'?K

Facade anchor withdisc and steel screw with

1 , 5 1 2 1 7 . 5Tl

- - r - l

2.6.25 Heat losses via various tvoes of anchors

neaoanchor with

electrogalvanized steel screwwith plastic coatinq

0.0080.004

Facade anchor withV4A stainless steelscrew with

0.002

Facade anchor withthermal break

2.6.26 Recommen.qed values for total energy transmittance of transparent components to DIN 4108 part 6Transparent component Total energy transmittance

Y I

Single glazingDouble glazingHeat-absorbing double glazing with selective coatingTriple glazing, standardTriple glazing with 2{old selective coating

0.870.760.50 to 0.700.60 to 0.700.35 to 0.500.20 to 0.50Solar-control glass

Translucent thermal insulation035 to 060

-Translucent thermal insulationThermal insulat ion, 100-120 mm;0.8 Wm'?K < U" < 0.9 Wm'?KAbsorbent opaque thermal insulation with s-[lgle layer glass cov aPProx. Or]0

167

Building scienee

System U-value

w/m2K

0.30 - 0.50

0.30 - 0.45

S

NR\t tM_I--1 1

t)\R[t\Til\T'E

\E--f--__-ll

0.20- 0.40

0.25 - 0.40

0.30 - 0.50

0.40 - 0.50

2.6.27 Ranges of standard thermal transmittance Ufor various external masonry walls

loss value c in W/K or the thermal bridge sur-charge AU in Wm2K is specified depending onthe construction of the support system and thethermal resistance of the loadbearing construc-tion (influence of transverse conduction). Theeffect of a thermal break is shown in fi7.2.6.28,a thermally advantageous supporting construc-tion in fig.2.6.29. Figure 2.6.27 is an overviewof the thermal transmittance values for a num-ber of different wall constructions.

Windows

The window as the "thermal hole" in the build-ing envelope is now a thing of the past. Tech-nological developments in insulating glazingsystems have set standards in the energyassessments of heated buildings. The reductionin transmission heat losses and maintenance ofa sufficient total energy transmittance for thepassive use of solar energy mean that windowscontribute to the heat gain during the heatingseason. However, the areas of glazing do havetheir l imits in terms of thermal insulation duringthe summer, when they can lead to uncomfort-ably high interior temperatures. The thermaltransmittance U* of a window depends on:' the distance between the panes' the number of panes. the emissivity of the glass surfaces towardsthe cavity

. the gas fi l l ing in the cavity between the panes' the hermetic edge seal of insulating glazing' the material of the frame.

The thermal transmittance U* can be takenfrom tables according to DIN EN ISO 10077part 1 (table 2.6.30) for constant frame propor-tions of 20 or 3O%, depending on the glazing(U") and the type and design of the frame (Ur),orijetermined by a simple area-based assess-ment of the U-values for glazing and frameincluding a surcharge for the glass seal aroundthe perimeter. Timber and plastic frames pro-vide good thermal insulation; the inside andoutside surfaces of metal frames must be care-fully separated (thermal break). Widening thecavity between the panes only improves theUo-value up to a certain width depending onthb type of glass (for air about 20 mm). lf thiswidth is exceeded, then the improvement tothe thermal insulation properties is counter-acted by convection. By employing noblegases (argon, krypton, xenon), we can exploittheir lower thermal conductivity (compared toair). The heat transport by way of radiationcharacterized by the emission behaviour of theglass surfaces can be drastically reduced byusing low-E coatin.gs. The development of low-E glazing began with sputtered, later pyrolyticcoatings and an air f i l l ing to the cavity; thisbrought Un-values of 1.8 Wm'zK. Today, doubleglazing with magnetron coatings and noblegas fi l l ings reach Ug-values of 1.1 Wm2K. Andmodern triple glazing systems based on silver

coatings and noble gas fi l l ings have alreadyreached peak values between 0.7 and 0.4W/m2K.

The permeability of the window for solar radia-tion is expressed by the total energy transmit:tance g. This corresponds to the percentageproportion of ineident radiation that passesthrough the glazing into the interior of the build-ing. As the glazed surfaces are generally notpositioned perpendicular to the solar radiationand so part of the solar energy is lost throughreflection at the pane, the total energy trans-mittance is reduced by 15%. Furthermore,permanent shade, from pads of the building,trees, neighbouring buildings, window ftamesetc., as well as the degree to which the solarenergy supplied is used must be taken intoaccount when calculating solar heat gains. lfno individual figures based on measurementsare available for the total energy transmittance,the design values given in fig. 2,6.26 may beused. These values cover the lower, i.e. lessfavourable, range of permeability of insulatingglazing with respect to the solar gains in theheating season. Figure 2.6.31 shows the ther-mal balance of two windows with double andtriple glazing during the heating season in areference environment (1 0"C heating threshold-temperature, degree days factor 2900) com'oared to the heat losses of a well-insulatedexternal wall. The Un-values are achieved byusing coated glasses and gas fi l l ings to thecavity. lt can be seen that double glazing witha combination of higher Uo-value but lessfavourable total energy trahsmittance hasadvantages on the southern side but for otherorientatjons exhibits slight disadvantages com-pared to the triple glazing. The latter is notused so widely because of the considerablyhigher weight of the glass. In the search forsolutions with even lower thermal transmittancevalues, countersash and coupled windowsoffer good alternatives in certain circum-stances. The much better insulated externalwalls of modern buildings render it necessaryto pay special attention to the detail at the junc-tion between the window and the wall, or theposition of the window in the wall. Poor designor workmanship can have a considerableeffect on the heat losses. Various windowarrangements in monolithic masonry walls withexternal, cavity and internal insulation havebeen investigated with respect to their heatlosses via the window reveals and masonry[45]. Figure 2.6.32 shows the best positions fot:windows in different masonry wall construc-tions.DIN 4108 supplement 2 contains window sil l ,reveal and head details for monolithic masonryor masonry with external or cavity insulation.An extract showing details for a wall with cavityinsulation is shown in fig. 2.6.33.

168

Thermal insulation

Translucent thermal insulation (Tl)

In contrast to normal opaque thermal insulationattached to ihe outside, Tl allows the incidentsolar radiation to pass through the insulationmaterial. The radiation is then absorbed andconverted into heat at the loadbearing wall. AsTl functions as thermal insulation, the heat lossto the outside is considerably impeded and themajority of the solar energy is conveyed asheat to the interior behind the Tl wall. As fig.2.6.34 shows, conventional, opaque thermalinsulation converts the incident solar radiationinto heat at the external surface and then radi-ates the majority of it back to the external envi-ronment. Only a negligible proporlion of theabsorbed incident solar radiation is transmittedthrough the wall to the interior. But the wel-come passive use of solar energy during thewinter can lead to undesirable heat gains dur-ing the warmer months of the year. The lowerthe thermal conductivity and storage capacityof the absorbent surface of a Tl wall, the hotterit becomes upon the incidence of solar radia-tion. This means that the absorbent surfacebehind a Tl wall can reach oeak temoeraturesof 100'C and more with very l ightweightmasonry compared to maximum temperaturesof 70'C for very heavy masonry. The translu-cent thermal insulation must be provided withsunshading for such situations. The more inten-sively the sun can shine on the facade, thehigher the heat gains of a Tl wall are. Thismeans that the energy gains are greatest for asouth orientation, the lowest for a nodh orien-tation. The heat losses during the heating sea-son outweigh the benefits in the case of a nodhorientation. Tl surfaces facing east and westexhibit an even energy balance. Clear gainshave been recorded for south-facing Tl sur-faces during the heating season. The thicknessof the masonry has no significant effect on theenergy gains of a Tl wall, Nevertheless, whenplanning a Tl building it is important to con-sider the thickness of the masonry behind thetranslucent thermal insulation as this influencesthe delay between maximum incidence of solarradiation and the heat being passed on to theinterior. This delay is about 4 hours for walls175 mm thick, about 6 hours for walls 240 mmthick and about B hours for walls 300 mm thick,virtually irrespective of the type of wall material,Consequently, the time at which the heat ispassed on to the interior is decisive for thecomfort of the user. The thermal and energyeffects and the influence of climate, materialparameters and construction details have beeninvestigated in a project sponsored by Ger-many's Federal Ministry for Research andTechnology [63].As the use of translucent thermal insulationfrequently leads to excessive heat which can-not be used, the cost-benefit ratio can be con-siderably influenced in individual cases by pro-viding only a partial covering of translucentthermal insulatlon. The area of translucent

2,6,28 Thermal bridges in ventilated curtain wall facades; influence of thermal break betlveenaluminium bracket and fixino substrate

Discrete thermal bridge loss coefficient 1 (W,4()

o . 1 2

0 ,1 1

0 , 1 0

0.09

0.08

o.o7

0,06

0,05

0.04

0.03

0.02

0.01

0.00

Substrate for fixings

Bracket fixing point

Thermal insulation

Bracket sliding point

T-section support

hermal break

with thermal break

0 0 .1 0 .2 0 ,3 0 .4 0 ,5 0 .6 > o .7

Thermal resistance R of fixing substrate (m2K,AiV)

2.6.29 Thermal bridges in ventilated curtain wall facades; rail systems of chromium-nickel steel withgood thermal performance

0.03

/,/ Substrate for fixings

thermal break

Facade fixing withbase plate andperforated plate

Serrated rail

Spacer withthermal break

Thermal insulation

0.0] -

0.6 > 0 . 7

Thermal resistance R of fixing substrate (m2K V)

2,6,30 Thermal transmittance_oJ windows to DIN EN IS9llSZZIe4 1

Wm2KProporlion ot tra qa 30%1 .0 1 .4 r .8 2 .2 2.6 3.0 3 ,4

5 .7 4.3 4.5 4.5 4.6 4.8 4.9

f f i n z8 zg -s.t

3z 3.4

0.50.4

Type ofglazrng irfr.,x

7 .O3 .8Single

Doubiit---glazrng

5 . 1 o . l

3 . 12 .92 .72.52.3

2.6 2 .7 2 .8 2 .9 3 .1 3 .22 .4 2 .5 2 .7 2 .8 3 .0 3 .12 .3 2 .4 2 .5 2 .6 2 .8 2 .92.2 2.3 2.4 2.6 2.7 2.82 .1 2 .2 2 .3 2 .4 2 .6 2 .7

3,5 3.6 4.43.3 3.5 4,33 ,2 3 .3 4 .13 ,1 3 .2 4 .03 .0 3 .1 3 .92.8 2.9 3.82 .7 2 .8 3 .62.5 2.7 3.52.4 2.5 3.32 .3 2 .4 3 ,22 .1 2 .2 3 ,1

1 , 9 2 2.2 2.3 2.4 2.6

1 . 7l . c

1 . 31 . 2 1 . 3 1 . 5 L 6 1 . 71 .7 1 .9 2 .O 2 .1 2 ,9

1 .8 1 .9 2 .0 2 .1 2 .3 2 .41 ,6 1 .8 1 .9 2 .0 2 .2 2 .31 . 5 1 . 6 1 .7 1 . 9 2 .O 2 .11 . 4 1 , 5 1 . 6 1 . 7 1 . 9 2 . O

2 .0 2 .1 2 .2 2 .4 2 .5 2 .71 .9 2 .0 2 .1 2 .2 2 ,4 2 .51 . 7 1 . 8 2 . 0 2 . 1 2 . 3 2 . 41 . 6 1 . 7 1 . 8 1 . 9 2 . 1 2 . 21 . 5 1 , 6 1 .7 1 , 9 2 .0 2 .11 . 4 1 , 5 1 . 6 1 . 7 1 . 9 2 , O1 . 2 1 . 3 1 . 5 1 . 6 1 . 7 1 . 9

Tripleglazrng

2.32 .11 . 91 . 7L C

1 , 31 . 10 ,9o ,7

ze -2e

3.72.6 2 .8 3 ,62 .5 2 .6 3 .42.4 2.5 3.32 .3 2 .4 3 .22 .1 2 .2 3 .12 .0 2 .1 2 .91 .8 2 .0 2 .81 .7 1 .8 2 .6

1 . 2 1 . 3 1 . 4 1 . 6 1 , 70 . 9 1 . 1 1 . 2 1 . 3 1 . 5 1 , 6

9,5 0 . 8 0 . 9 1 . 0 1 . 2 1 , 3 1 . 4 1 . 6 1 . 7 2 . 5

Note: Calculated using y-values from appendix E. Values for windows whose frame proportion * 30% should be

determined us.lllg_the equations in the main.part of this standaF,

Building science

I

2.6.31 Thermal balanceofwindowsoveraheat ingseasonforareferencelocat ioninGermany

KWh/HP m 2

! Double glazing Us=1.2

T r i p l e g l a z i n g U s = 0 . 8

E x t e r n a l w a l l r r _ ^ ea s c o m p a n s o n " - " . "

thermal insulation is typically between 10 and3Oo/o of the total area of insulation. ln choosingwhich areas to cover, architectural aspects,the orientation of the facade, the planned useof the interior and the amount of space avail-able on the facade all play a role. A solar ener-gy system consisting of a translucent layer ofpolycarbonate with a capillary structure and afinal coating of translucent plaster has provedto be an especially practicable option [204].One important advantage of the system is thatin summer a large part of the incident solarradiation is reflected at the surface of thetranslucent plaster, and so expensive andtroublesome shading systems are generallyunnecessary.

Solar gains of opaque external walls

External comoonents absorb direct or diffuseincident solar radiation. Thus, the outer layersof the component heat up first and the heat isconducted to the inside of the component.This process reduces the heat transfer throughthe external component. The heat gain due toradiation deoends on the available solar radia-tion and hence on the orientation and colour ofthe component's surfaces, any shading tothose surfaces and the external surface resis-tance, The reduction in transmission heatlosses which can be achieved due to theabsorption of radlation by an opaque externalwall is proportional to the U-value of the ex-ternal wall. Whether the construction has oneor more layers is virlually irrelevant; likewise,the sequence of layers in a multi- layer con-struction.The annual solar net heat gains from opaquesections of the building envelope withouttranslucent thermal insulation constitute only afraction of the total solar heat gains and arepartly offset by the radiation heat losses fromthe building to a cloudless sky. Therefore, theycan usually be ignored. Table 2.6.35 containssolar gain factors for common external walls.The thermal transmittance of an external wall isonly reduced by 2-12% by the radiation influ-ence for average climatic relationships. TheFraunhofer Institute for Building Physics hasreached similar conclusions in a computer-assisted experimental study on buildings withmonolithic and multi- layer external walls [198].

9 = 0.65

9 = 0 . 5

%20

South EasWVest Opaque

2.6.32 Position of window in wall for different types of walls+ small heat flow via window reveal- large heat flow via window reveal

Position olwindow inwatl

Type of external wall according to table 1

External insulation Cavity insulation Internal insulationMonolithic

Outside

l7t4ttffif././/-wT

Central

lns ideruwwl

3m+ffi

170

Thermal insulation

Heat storage

The interior heats up and cools down, the sunshines on the outside and rapid changes tothe air temperature take place on both sides ofcomponents. These effects lead to temperaturechanges and changes to the heat f lows whichcannot be taken into account by the thermalresistance R or the thermal transmittance U. lnthese cases the heat storage capacity of thematerials and components in conjunction withthe time play a decisive role.For a mathematical analysis with numericalmethods we require variables derived from thespecific heat capacity, the thermal conductivi-ty, the gross density and the thickness of thematerials concerned. The heat storage capaci-ty Q", i,e, the amount of thermal energy inJ/m2K stored in 1 m2 of a slab-like componentof thickness d in m made from a material withdensity r in kg/m3 for a 1 K temperature rise, ina homogeneous construction is given by

Q " = c x P x d

The propagation of a temperature zone in amaterial is described by its thermal diffusivity ain m7s. As the a-value increases, so the tem-perature change in a material spreads faster.The thermal diffusivity is derived from the ther-mal conductivity I, the specific heat capacity cand the density p of the material concerned:

)rA _

o x c

The thermal diffusivity of building materials l iesin the range 0.4 to 1 x I 0 6 m7s depending onbulk density (t imber = approx. 0.2 x 10-6 m7s,steel = approx, 2.0 x 10-6 m7s). The heat pene-tration coefficient of the material concerned isthe governing variable when assessing thebehaviour of materials subjected to brief heatflow processes such as the heating and cool-ing of walls. The heat penetration coefficient bis derived from the thermal conductivity 1., thespecific heat capacity c and the density p ofthe material concerned :

O = y T x p x c

The b-values of some building materials aregiven in table 2,6.36. Figure 2.6.37 shows theheating and cooling behaviour for a change ininterior air temperature of 15 K for two differentwall constructions with approximately equalthermal resistance. Rapid heating-up of thewalls is desirable from the point of view ofcomfort - with the heating operated briefly,However, the lighter component cools downquicker after switching off the heating. Practi-cal investigations of the influence of the heatstorage capacity all lead to the same result -that the influence of the heat storage capacity,especially that of external walls, on the energyconsumption for the heating of a building is

relatively small. Theoretical studies have pro-duced the same result 1741. Therefore, thequestion of whether the heat storage capacityor the thermal insulation of external compo-nents is more important from the point of viewof saving energy can be answered: it definitelydepends on thermal insulation. The importanceof the thermal transmittance as the basis forcalculating transmission heat losses throughexternal walls is undisouted. Studies of build-ings with the most diverse external masonrywalls have revealed that despite severely fluc-tuating external climatic conditions quasi sta-tionary heat flows become established after, atmost, one week and the U-value adequatelydescribes the heat losses through the opaqueexternal surfaces of a building [2]. However,heavy components, which are thus suited tostoring heat, do have a positive effect on theinternal climate because they cool down slowerwhen ventilating the interior or after switchingoff the heating and hence maintain the interiorair temperature at a comfortable level for alonger period. The amount of heat lost throughventilation and transmission remains, however,the same as for the lighter type of construction.

We must distinguish between two opposingphenomena with regard to the effect of theheat storage capacity on the annual heatingrequirement. The heat gains due to internalheat sources and incident solar radiation canbe better used by the heavy construction thanthe l ightweight construction because overheat-ing of the interior is considerably lower in theformer. This effect is rewarded with a betteruse of the heat gains. In contrast, the behav-iour of the l ightweight construction is morefavourable than the heavy construction in thecase of a night-time temperature reductionbecause the internal air temperatures can fallmore rapidly and hence the heat losses aresmaller. lt is not possible to make generalizedstatements as to which type of construction isbetter in terms of heating energy consumptionbecause of the opposing effects of a night-timetemperature reduction and overheating.During the warmer months of the year the heatstorage capacity of the internal components ofa building exerts a compensating influence onthe internal air temperature gradient. lf the heatfrom the sun is stored in the componentsbefore being radiated to the internal air, insummer we enjoy a pleasant, balanced internalclimate even when cooler temperaturesalready prevail butside. DIN EN 13786 stipu-lates characteristic values related to thedynamic thermal behaviour of complete com-ponents and specifies methods for their cal-culation.The characteristic values defined in the stan-dard can be used as product specifications forcomponents or for calculating'the internal temperature in a room,. the daily peak performance and the energy

2.6.33 Favourable window position to DIN 4108supplement 2 to reduce thermal bridge effect(fulljil l cavity wall)

2.6,34 The function of translucent thermal insulation^^m^.r6d +^ ̂ n.^t 'a thermal inSUlation

Transparent

Incident solarradiation

Heat radiation

Incident solarradiation

Heat radiation

Building science

SouthEasywestNorth

2.6.35 Solar gain factors for common external wallssubiected to averaoe climatic conditions [2131

Orientation Common external wallLiqht colour Dark colour

requirement for heating or cooling,. the effects of intermittent heating or cooling.

Thermal bridges

These are weak points in the thermal insulationof the building envelope at which - comparedto undisturbed, neighbouring sections of thecomoonent - additional heat losses and lowerinternal surface temperatures occur. Varioustypes of thermal bridges are possible depend-ing on the way in which they are formed:. Geometric thermal bridges ensue when the

heat-absorbing and heat-radiating surfacesof the comoonent are of different sizes. Theclassic example of a geometric thermalbridge is the corner of an external wall.

. Material-related thermal bridges depend onthe construction of the building and thearrangement and combination of componentswith materials of different thermal conductivi-ty. Typical thermal bridges of this kind areroof bearings, parapets, balcony floor slabsand columns in external walls.

. Detail-related thermal bridges can ensue incomoonents due to mechanical connectionswhich penetrate or bypass the thermal insula-tion. These include anchors in concrete sand-wich walls and multi- leaf walls, and all con-structions in metal and timber.

Measures for avoiding or reducing thermalbridges are certainly necessary to avoid con-densation on internal surfaces, and suchmeasures are generally taken. However, theremaining - in energy terms - weak points withhigher heat losses are usually not taken intoaccount when assessing thermal performanceand the heating requirement of a building. Tosome extent the additional heat losses via ther-mal bridges are balanced by the fact that thetransmission heat losses of a building are cal-culated with reference to the outer surface,which is too large, particularly in the case ofthick, monolithic masonry constructions. As thestandard of thermal insulation of the buildingenvelope rises and the thermal transmittancevalues drop, so the thermal bridges play anincreasingly significant role. Therefore, theincreased heat losses must be investigated atthe planning stage when calculating the heat-ing energy requirement for the building. Thiscan be done in different ways. Thermal bridgesdue to the structure itself, e,g. edges, corners,roof bearings, balcony floor slabs etc,, canonly be calculated accurately with the help ofcomputer techniques. However, for the pre-liminary design of a building and assessmentof the energy effects of the building envelope,it must be possible to estimate the effects ofthermal bridges without major mathematicalanalyses. With the help of correction values totake into account continuous and discrete ther-mal bridges, DIN EN ISO 14683 gives the ther-mal conduction of the building envelope as

L = x U i x A , + x Y o x l ^ + E 1 ,

where:L thermal conduction in W4(Ui thermal transmittance of building envelope

component i in Wm2Ksurface area applicable for U,thermal transmittance of continuous ther-mal bridge k in WmKlength applicable for Y^thermal transmittance of discrete thermalbridge j in Wl(.

The thermal transmittance Y is normally takenfrom thermal bridge catalogues. The examplesof building details contained in these cata-logues are essentially based on fixed parame-ters (e.9. dimensions and materials) and aretherefore less flexible than calculations. Thecatalogue examples often do not correspondexactly with the component being investigated.Consequently, the use of Y-values from cata-logues leads to uncertainties about thosedetails. Nevertheless, the Y-value from a cata-logue can be used, provided the dimensionsand the thermal properties of the catalogueexample are similar to those of the buildingdetail, or the catalogue example is lessfavourable in thermal terms than the buildingdetail. The Y-values in a thermal bridge cata-logue must have been derived from numericalcalculations according to DIN EN 10211 parI2.Thermal bridge catalogues offer solutions todetails from basement to roof - for wall, win-dow, floor and balcony junctions (see fig.2.6.38), DIN 4108 supplement 2 containsdesign and construction examples for thermalbridge details; the masonry details includejunctions for monolithic external walls withexternal and cavity insulation. Figure 2.6.39shows the junction details for ground slab,basement roof (ground floor), upper floor slabsand flat roof with parapet for a monolithic exter-nal masonry wall 365 mm thick. A balcony floorslab projecting from the structure acts like acooling fin owing to the increase in the externalsurface area; figure 2.6.40 shows how the bal-cony junction can be thermally isolated fromthe floor slab. The layer of thermal insulation isonly penetrated at individual points by the rein-forcing bars. This cuts the thermal transmit-tance Y by 50% compared to a continuousconcrete slab. A steel curtain wall constructionconnected to the floor slab by a tension rodexhibits a similar reduction in thermal bridgelosses. Applying thermal insulation to the topand bottom of the cantilevering balcony slabbrought practically no worthwhile success. Interms of the thermal bridge effect of a wholevariety of construction details for baleony junc-tions, there is no difference betvveen single-leafwalls, walls with thermal insulation compositesystem and multi-layer external walls.

0.040.030.o2

o . 1 20,070.06

2.6.36 Heat penetration coefficients for some buildingmaterials

Building material Heat penetration coeff icientJ/so smrK

Normal-weight concretedepending on gross densityLightweight concretedepending on gross densityClay brjcksTimberFoamed plastics

AiY.,

' K

x11 600 to 2400

250 to 16001000 to 1300500 to 65030 to 45

2.6.37 Chronological progression of interior surfacetemperature Ooi for various external walls withapproximately equal thermal resistances afterincreasing or decreasing the internal air temper-atur€ OLi by 15 K ('C) [62]

R = 1 ,50 m2l (W

Wall 1 - 24Omm aerated concretei 500 ko/m 3l -

i, = 0.16 w(mK)

ooi

Yri

0 5 1 0Heating up (h)

F = 1.55 m2 KAV

Wall 2

or' = 5"c

ou = 5'c

t c

O

o

E r nooEo

p 60 mm polystyrene, 30 kg/m3l, = 0.040 W(mK)

. 100 mm normal-weight concrete2500 kg/m J

f l f l t ^ = 2 1 w ( m K )

[1 LnH I s . '

t c(_l

o

i . n

ooEo

F -' c

I

't72

Thermal insulation

Osi

oifl

The thermal influence range of thermal bridgescan lead to noticeably lower sudace tempera-tures on the inside and to condensation, whichmay lead to the growth of mould. Specifyingthe interior surface temperatures in "C deter-mines - to a l imited extent - the additional stio-ulation of external and internal air temperature.As very different boundary conditions may bechosen depending on use and meteorologicalcircumstances, the surface temperature is usedin a d imensionless form by DIN EN ISO 10211part 2 according to the following definit ion:

f*" , = (O"1 -Oe)/ (Oi -O")

where:f*., temperature factor at location of thermal

bridgeinternal surface temperatureinternal air temperatureexternal air temperature.

To avoid the groMh of mould, according toDIN 4108 part 2, the minimum requirement fRsi> 0.70 must be fulf i l led assuming an internal airtemperature of 20"C and 50% relative humidityfor an external air temperature of -5"C * a notinfrequent occurrence in Germany under aver-age meteorological l imits. In this context theminimum thermal resistance for an externalwall R = 0,55 m2KAfi must be increased toR = 1.2 m2KM in order to also maintain thetemperature factor 0.70 at the corners of ex-ternal walls according Io 2.6.41 assuming aninternal surface resistance R"i = 0.25. Thismeans maintaining an internal surface temper-ature of O"i > 12.6'C for the said l imits. As arule, the stipulation in DIN 41OB part 2 that allconstructional, form-related and material-related thermal bridges given as examples inDIN 4108 supplement 2 can be regarded asproviding adequate thermal insulation forms asimple criterion for the avoidance of mould forthe designer and operator of a building. In thecase of thermal bridges in components adjoin-ing the soil or unheated basement rooms andbuffer zones, we must assume the conditionsgiven in f i7 .2.6.42.fhe establishment of thermal bridges can becarried out by experiment or by analyticalmeans. The simplest method is the determina-tion of the internal surface temperatures in theregion of a thermal bridge by way of discretemeasurements and reference to the tempera-ture limits on both sides of the external compo-nent. Thermographic techniques involve theuse of an infrared camera to provide a thermalimage of the exterior of a building elevation orthe internal surfaces of individual rooms. Thismethod supplies important information aboutthe condition and quality of thermal insulation.Defective workmanship or the success ofupgrading the insulation to a building can bemade visible. However, an infrared photographcannot help us to make quantitative statements

about the extent of thermal losses. Temoera-ture distribution and heat transfer can be deter-mined for faithful replicas of components inlaboratory tests according to DIN EN ISO 8990,in which the component is incorporated as aoartition between two soaces at different tem-peratures. The mathematical determination ofthe effects of multidimensional thermal bridgesis carried out by calculating the temperaturezone and heat f low using the numerical solu-tion of the three-dimensional thermal conduc-tion equaticn. lf adequate for the particularcase, the calculation for furo-dimensional planerelationships is carried out and, in the.case ofclear three-dimensional temperature and heatflow zones, extended to three-dimensionalslruclures.

2.6.38 Some details used in a thermal bridge catalogue(Hauser) for specifying Y- and f-values

Wall junction Floor junction

Wndow junction Balcony junction

2.6.39 Junction details for a single-leaf external wallaccording to DIN 4108 supplement 2

Building science

2.6.40 lmproving the thermal performance of balconyfloor slab junctions

+

Airtightnessl

As the requirements for thermal insulationincrease, so the airt ightness of the buildingenvelope becomes more and more important.A high degree of imperviousness is necessaryin order to really achieve the desired reductionin heating energy requirement and avoid dam-age to the building as well as a drop in thestandard of comfort. Uncontrolled leakage fromthe building wrecks all other measures forincreasing the thermal insulation. Therefore,partial optimization, l ike minimizing U-valueswithout taking into account such leaks, aretotally ineffective in practical terms. The air-tightness of a structure must be consideredindependently of the exchange of internal andexternal air. This exchange of air is necessaryto maintain a hygienic internal climate and istaken into account when caiculating the heat-ing energy requirement by way of the ventila-tion heat losses with a defined air change rate.The air change rate is accomplished naturallyby opening the windows or by way of mechani-cal ventilation systems. So, leaks in externalcomponents represent additional uncontrolledventilation heat losses which can be avoided orat least minimized according to the state of thean.A non-airtight building envelope usually resultsin several unwanted effects:

. Draughts impairing the comfort of occupants

. Condensation damage resulting from watervaoour convection of the moist internal air tocold external zones of enclosrng components

' Lowered sound insulation against external noise' Energy losses that form a considerable pad of

the total energy losses of a building.

The airt ightness of buildings as well as individ-ual residential units or rooms within a finishedbuilding is determined according to DIN ENISO 9972 (blower door). This international stan-dard specifies the use of mechanical overpres-sure or underpressure applied to buildings.The airt ightness is generally defined by theremaining air change rate of the building orpart of the building at a pressure difference of50 Pa (nro-value). The airtightness can beassessed on the basis of the nuo air changerates given in table 2.6.44. Thresholds for theair change rate were first laid down in DIN4108 part 7. The n.o-value for buildings withnatural venti lation is l imited to 3.0 per hour, forbuildings with mechanical venti lation 1.0 perhour, ln addition to the reouirements of thestandard, it is considered adequate, taking intoaccount practical building tolerances, whenthe measured air flow rate, related to the vol-ume of air in the room, exceeds the thresholdgiven in the standard by up to 0.5 per hour at apressure difference of 50 Pa.As might be may expected, masonry buildingsgenerally have a better airtightness than light-weight types of construction. However, even in

the case of masonry, penetration of the internalplaster, window junctions, false wall installa-tions and roof junctions must be carefullydetailed. DIN 4108 part 7 contains importantand useful design and construction recornmen-dations, and shows - see fig. 2.6.43 - details ofoverlaps, junctions, penetrations and joints inthe plane of imperviousness.

Requirements for thermal insulation

The design, calculation and measuring stan-dards provided in CEN/TC 89 "Thermal perfor-mance of buildings and building components"form the basis for the National ApplicationDocuments of the series of standards belong-ing to DIN 410B "Thermal insulation and energyeconomy in buildings". The type and extent ofrequirements is still a matter for the individualcountries. In order to maintain minimum require-ments and plan energy-saving measures, thefollowing parts of DIN 4108 must be adhered to:parl2: Minimum requirements for thermal

insulationpart 4: Characteristic values relating to

thermal insulation and protectionagainst moisture

oart 6: Calculation of annual heat andannual energy use

v o r r / . Airti ghtness of building componentsand connections; recommendationsand examples for planning and Per-formance

supp. 2: Thermal bridges - examples forplanning and performance

DIN 4108 part 2 specifies the minimum require-ments for the thermal insulation of componentsand thermal bridges in the building envelope. ltalso contains advice pertinent to thermal insu-lation for the design and construction of occu-pied rooms in buildings, the use of whichrequires they be heated to common internaltemperatures (> 19'C). Minimum thermal in-sulation is understood to be a measure thatguarantees a hygienic interior climate; withadequate heating and ventilation assuming aconventional usage, at every point on thelnternal surfaces of the building envelope sothat no condensation forms over the wholearea, nor in corners. Apart from that, the risk ofmould growth is diminished. Major changes inthe 2000 edition compared to the 1981 editioninvolve practically the doubling of the minimumvalue for the thermal resistance of externalwalls from R > 0.55 to R > 1 .2m2KNtl, the moredetailed treatment of thermal bridges, meas-ures for avoiding the growth of mould and thesimplif ied assessment of minimum thermalinsulation for heavy and lightweight compo-nents. We now only distinguish between com-ponents with a surface-related total mass of atleast 100 kg/m3 and components with a lowertotal mass without taking into account the posi-tion of layers of insulation and their effect onheating and cooling processes. The fact that

ed

o

H 0.8o=6@ i 7o " . ,EoF

2.6.41 The temperature factor at an e)iternal wall corneras a function of the thermal resistance of theexternal wall for two different thermal trans-mittance values

36.5 cm

0.6

7f n", = o.as

174

Thermal resistance R

Thermal insulation

lower storage mass is compensated for bybetter thermal insulation is solved simply byapplying enhanced requirements withR > 1 .75 m2K/"N for components < 100 kg/m3,which corresponds to the former maximumvalue for l ightweight components, In the caseof structural frames, the value applies only tothe infi l l panels. In these cases an average ofR > 1.0 m'zKAN is to be maintained in additionfor the entire comoonent. Fufther details havealready been described in the sections onthermal bridges and airt ightness.

Energy-savings ActPutting figures to the requirements for energy-saving thermal performance is the object ofpublic-law statutes aimed at energy-savingconstruction, The stipulation of an annual ener-gy requirement in the Energy-savings Act cor-responds to a oerformance class for differentmethods of energy-saving defined in principaldocument No. 6 "Energy economy and heatretention". The European standard DIN EN 832serves for its technical imolementation. Thisstandard refers to a series of further designstandards, such as the calculation of the spe-cific heat loss coefficient, heat transfer to thesoil, dynamic thermal parameters and the treat-ment of thermal bridges. The raw data for thedesign standards includes product features,e.g. the thermal conductivity of insulation ma-terials and masonry constructions. The logicalconnection between the various design, pro-duct and measuring standards is i l lustrated infig. 2.6.45. Furthermore, national boundaryconditions, e.g. climate data, solar gains, inter-nal heat sources and air change rate in DIN4108 part 6, as well as provisions for dealingwith total heat losses from a heating systemand the heating requirement for hot water sup-plies to DIN 4701 part 10, sti l l have to be spec-ified in order to finalize the European method ofanalysrs.Experience has shown that ambiguous desig-nations and confusion often arise when des-cribing thermal insulation and energy proper-ties. Therefore, the following definitions areintended to provide clarity:' Heating requirement: heat to be delivered tothe heated space to maintain the temperatureover a period of time.

' Heating energy requirement: the calculatedamount of energy that must be fed into theheatlng system of a building to be able tocover the heating requirement.

' Heating energy consumption: the amount ofheating energy (energy carrier) measuredover a certain period which is required tomaintain a certain temperature in a zone.

. Final energy requirement: the amount ofenergy which is required to cover the annualheating energy requirement and the heatingrequirement for the provision of hot water,determined at the system boundary of thebuilding under consideration.

' Primary energy requirement: the amount ofenergy required to cover the final energyrequirement, taking into account the addi-tional amounts of energy consumed by up-stream process chains beyond the systemboundary of the building during the produc-tion, conversion and distribution of the fuelused.

Up to now, the heating requirement has beensubject to certain stipulations, but the newstandard is coupled to the heating energyrequirement, i.e, the primary energy evaluation,in order to incorporate the efficiency of theplant and the energy carrier used. This meansthat the balance framework, which previouslyended at the radiator, now extends back to thepower station or to the supply of gas or oil.One key element in the Energy-savings Act isthe stricter framework of requirements forenergy-saving construction, the aim of which isto cut consumption by an average of 3O7o fornew building work and to bring the previousthermal insulation and technical olant require-ments and upgrading rules, as applied to theexisting building stock, up to the current tech-nological level. As in the Thermal lnsulationAct, this act covers buildings with normal inter-nal temperatures (min. 19'C); the definit ion forbuildings with lower internal temperaturesremains unchanged.Buildings with normal internal temperaturesmust comply with maximum figures for theannual primary energy requirement (see fig.2.6.46), depending on the type of buildingAl/e. The specification of the primary energy isintended to create a clear l ink to the polit icalobjective of reducing carbon dioxide emissionsand avoid a distortion of the market for com-peting energy systems. On the other hand, thecalculated final energy provides valuable infor-mation for the user as a standardized oredic-tion of the consumption to be expected and atthe same time forms a parameter in an "energyrequirement pass" specific to the building. Theadditional ancil lary requirement covering themaximum annual heating requirement isintended to ensure that the orevious standardof thermal insulation to the building envelope ismaintained.Requirements for the imperviousness of ex-ternal windows and glazed doors remainunchanged. The imperviousness of the build-ing envelope is dealt with more precisely byproviding information on a suitable method ofmeasurement and permissible leakage rates.To guarantee energy-saving summer thermalinsulation, the previous provisions have beenimproved and tightened up in l ine with tech-nical progress.A limit to the cooling requirement has beenimposed on buildings which, because of theirfunction, demand a particular type of facadeand cooling in the summer. The minimum ener-gy requirements for starting up heating boilers,

2.6.42 f emperature limits to DIN 4108 part 2 for thermalbridge calculations

Part of building or surroundings Temperature e'cBasementSoilUnheated buffer zoneUnheated roof

2.6.43 Examples of sealing to DIN 4108 part 7

Junction between roof and plastered masonry wall

1 051 0

6 Sealing strip laminatedwith non-woven cloth

Junction between window frame and masonry wall

2.6.44 Au chanqe rates for airtightness tesl

Recommended values

Aidightnessof bui ld ing

Air change rate at 50 palhApartment Detached

very airtight 0.5-2.0moderatelyair t ight 2.0-4.0less ai r t ight 4.0-10.0

'1.0-3.0

3.0-8.08.0-20.0

Threshold valuesBuilding with Air changes per h

natural ventilationmechanical extraction

n s o 3 3nso < 1 ,5

1 Airtight layer4 U r d l r p i l r g u o r r s r r

3 Compressed sealing stripAdhesive

4 lnternal plaster

't75

Building science

Thermal performance of buildingsCalculation of heating energy requiremenl

Specific transmission heat loss coefficient

EN tSO 13370Thermal transmission via the soil

Draft EN 13786Dynamic thermal propertiesof components

1 l p a r t s 1 a n d

2.6.45 BreakdownofTC39standardizat ionworkandl inksbetvveenindiv idual standards

Energy-savings Act

Planning and design standardsBui ld ings

distribution apparatus and hot water systemsstipulated in the Heating Plants Act have beenincorporated essentially en bloc.As before, buildings with low internal tempera-tures only have to comply with a maximumannual transmission heating requirementbecause for these buildings the air change rateand internal heat sources can fluctuate quiteconsiderably depending on use.Changes to existing buildings necessitated theprevious provisions to be adjusted to therequirements for the thermal transmittance ofindividual components according lo tig. 2.6.47 ,Tighter stipulations for thermal insulation mea-sures to be carried out during refurbishmentwork were created so that correspondingimprovements affectin g energy requirementswould find a wide range of applications amongthe existing building stock. Within a specifiedperiod, the heating distribution pipes of a heat-ing system in an existing building must beinsulated and the boiler itself brought up to thestandard of new building work.

Method of calculation

The calculation of the heating and heatingenergy requirements is carried out by using theEuropean standard DIN EN 832 in conjunctionwith the National Application Document DIN4108 part 6 and DIN 4701 part1O. The methodof calculation according to DIN EN 832 isbased on a stationary energy balance butdoes. however. take into account internal andexternal temperature changes as well as thedynamic effect of internal and solar heat gains.The annual heating energy requirement is cal-culated according to fig. 2.6.48 by drawing upa balance sheet of the loss and gain variablesinvolved. Apart from the heating requirementdepending on the building, the heating energyrequirement also includes the technical lossesof the heating system, the energy requirementsfor hot water and possible gains from regener-ative systems. The losses of the system can becalculated accurately according to DIN 4701part 10 by way of quantity f igures for heattransfer, distribution, storage, generation andprimary energy conversion for each individualcase according to the plans available for thetechnical services or by using a quantity f iguree^ for the entire system related to the primaryehergy. Two methods are available for deter-mining the heating requirement. The simplerperiod balance method, also possible withoutthe use of a computer and restricted to resi-dential buildings, uses the equation

Qn = Qr, np - nHp x Qg, Fje

where:Q^ the heating requirement for the heating

seasonQ,,n, the heating losses during the heating

season

2,6.46

200

180

Stipulations for primary energy requirement

6

E 160c

? 1 4 0;co 1 2 nco

= 100oo> 8 0ooC ^ ^o o uoc

oI

20

Primary energyrequirement withhot water heatedby electric

Primary energyrequrrementwith hot waterheated by boiler

Primary energyrequirementwithout hot water

Energy-savings Act(Heating energy requirementl

0 0 ,1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 .0 1 .1

, 4 / 1 m - 1 1

2.6.47 Enerov-savinos Act (EnEV): measures for existinq buildinq stock

0

Component U-valueWm2kEnEV0,450.351 , 7 00.30o.250,400.50

External walls (internal insulation, renewing of infill walls)External wallsWindowsFloors, roofs, pitched roofs (steep)Floors, roofs, pitched roofs (shallow)Roofs and walls to unheated interiors or soil (insulation on cold side)Roofs and walls to unheated interiors or soil (insulation on warm side)

176

Thermal insulation

Qn,gp the heating gains (internal, solar) duringthe heating season

Tlnp the degree of uti l ization.

The more accurate monthly balance methodtakes into account further variables influencingthe heating energy requirement and broadensthe planning options. The annual heatingrequirement Qn is obtained by adding togetherthe individual monthly balances, providedthere have been positive values for eachmonth, using the equation

n _ s nv L - ! v ! ^ /! ' " " ' ' o o s

andQ n , v = Q r , v - n M x Q s , M

DIN 4108 part 6 contains the l imits for the heat-ing degree days, the average available solarradiation and the average monthly externaltemperatures and intensity of solar radiationnecessary for both methods of calculation. Ananalysis of thermal insulation according to pub-lic-law requirements must also apply the condi-tions described in DIN 4108 oart 6,The advantages of the monthly balancemethod are that the influences of lighter orheavier types of construction on the degree ofutilization of the heat gains and the effect of thenight-time drop in temperature, as well as solargains via glazed sections, opaque componentsand translucent thermal insulation can all betaken into account. The air change rate ofn = 0.7 per hour for natural venti lation, and itsreduction to n = 0.6 per hour if an airt ightnesstest is carried out an$ the condition n.o < 3 perhour is thereby fulf i l led, has a decisive influ-ence on the heat losses. A further reduction inventilation losses can be achieved by usingmechanical ventilation with heat recovery.ln the oeriod balance method the influence ofthermal bridges is determined by a global sur-charge on the specific transmission heat lossU

H * r = A U * r x A

AUwe = 0.05 Wm'?K can be used for con-structions comoarable in thermal terms withDIN 4108 supplement 2. The monthly balancemethod also permits thermal bridge losses tobe calculated using thermal transmittance val-ues (y-values).

In addition, quick implementation of DIN EN 832is made possible by means of global reductionmethods or correction values derived fromcomprehensive European standards requiringintensive mathematical analysis. This simplif i-cation has an effect on temperature correctionfactors for areas in a heated basement in par-ticular.Calculations carried out for individual types ofbuildings confirm that single-leaf masonry wallsare still possible with a higher standard of heat-

ing system (low-temperature boiler, condens-ing technology), with verif ied imperviousness,night-time drop in temperature, optimized dou-ble glazing and a high standard of insulation toroof and basement areas.ln such cases the thermal transmittance of theexternal wall should not exceed U = 0.40 Wm2K.Twin-leaf masonry with additional thermal insu-lation, single-leaf walls with thermal insulationcomposite systems or thermally insulated con-structions with ventilated outer leaves are allpossible without any problems.All the main energy requirement segments of abuilding are covered by an "energy require-ment pass" for the following purposes:. To provide the user with information about the

energy consumption to be expected.. To improve clarity in the housing and proper-ty market with respect to the quality of build-ings in terms of energy aspects.

' To support the implementation of the Act byputting the user in the position io check thefeatures of his building relevant to energy,and to investigate unusual aspects.

A simple summary shows that the heatingenergy requirement of a building is determinedby four factors:. Climate: location of building, external temper-

ature, incident solar radiation. Building: shape, volume, plan layout, orienta-tion, construciion of external components,type of construction

. Heating system: heat generation, regulation,distribution, hot water supply

. Use: internal temperature, air change rate,usable waste heat.

Thermal comfortThe thermal comfort in a heated room essen-tially depends on the surface temperatures ofthe surfaces enclosing the room and on the airtemperature within the room. The velocity andhumidity of the air, the activit ies of people inthe room and clothing also play a role. Thecomfort ranges of the individual factors arelinked. The air and surface temperatures influ-ence the temperature perceived by an occu-pant such that - within certain limits - a lowerair temperature can be compensated for by ahigher surface temperature (see fig. 2.6.49).There is a connection between the desiredhumidity of the air and its temperature, whichcan also be presented as a comfort range (seefig. 2.6.50). The degree of comfort perceivedby an occupant must be assessed differentlyfor each individual. Based on essentially physi-cal processes such as radiation exchange,conduction and evaporation, as well as gener-ally applicable experiences, a favourable inter-nal climate prevails when the following factorsare oresent:. The external components - with good thermal

insulation - have an internal surface tempera-ture of about 18"C.

. The difference between the air temperatureand the surface temperature of enclosingcomponents does not exceed 2 K.

. The relationship between air temperature andrelative humidity l ies, and is appropriatelybalanced, in the range of O = 1B-24"C and<P = 40-600/o.

. The air circulating in the interior does notexceed a velocity of 0.1 0-0.20 m/s.

Thermal insulation in summer

With suitable construction, mechanical coolingsystems are generally unnecessary in build-ings containing apartments or individual officesand other buildings with similar uses.Thermal insulation in summer essentiallydepends on the total energy transmittance oftransparent external components, their com-oass orientation and, in the case of roof win-dows, their inclination. Other factors are theventilation options in the rooms, the heat stor-age capacity (particularly internal compo-nents), and the heat conduction properties ofopaque external components subjectto non-constant boundary conditions. Effective sun-shades for transparent external componentscan be integrated into the construction by wayof overhanging roofs or balconies, by externalor internal blinds or by using solar-controlglass. The purpose of l imiting the ingress ofsolar radiation in the summer is to guaranteecomfortable interior temperatures, i,e. to avoidexceeding certain threshold temperatures formore than 10% of the occupancy time. In orderto keeo within temperature l imits in warmer cli-matic regions (with sunshades provided), thefollowing requirements have been laid down:

' summer climate region A;cool summer regions 25'C

. summer climate region B;moderate regions 26oC

. summer climate region C;hot summer regions 27'C

The fixed threshold of the dimensionless solarheat penetration Srr* must not be exceeded inan analysis. This value is calculated from thetotal energy transmittance of the glass g, theproportion of window area f in an elevation,and the reduction factor F" for sunshades aswell as the window frame component Fr:

Sru"z S = f x g x F" (1 - FF)/0.7

The threshold is calculated from a basic valueSo for the applicable summer climate region aswell as correction factors depending on con-struction and use according to table 2.6.51:

Sr"" 2 So + x, AS,

The following values apply for the designvalue S^:

177

Building science

\

* ?imi"QrQp- p

2.6.48 EN 832 (thermal performance of buildings): calculation of heating energy requirement Q (final energy) andprimary energy requirement Qp for residential bu;lding

summer climate region A So = 0.tBsummer climate region B So = 0.14summer climate region C So = 0.t0

According to DIN 4108 part 2, only the basicvalue So = 0.18 for cool summer regions isused as the minimum requirement for thermalinsulation in summer, lf the proportion of win-dows in a west to south to east orientation isless than 2Oo/o, or less than 3Oo/o for a north-east to north to north-west orientation, or lessthan 157o for sloping windows, an analysis isnor necessary.lnlhe differentiated method according to DIN4108 pad 6, the specified threshold for the so-

' o, called standardized, non-usable heat gains(which can also be interpreted as ovenemper-ature degree hours) must not be exceeded.The method of calculation makes it possible totake into account various factors, e.g. internalheat loads, orientation of facade, air changerate etc., accurately. The differentiated methodis particularly suitable for buildings with highinternal loads or enhanced passive solar ener-gy use. Buildings with interior cooling shouldbe init ially designed and constructed in such away that the stipulations for thermal insulationin summer are comolied with and the residuaheat is removed by using mechanical systems(see f ig . 2.6.36) .

Q Heating energy requirementQ, Heat gain from surroundings

(renewable energy)Qn Heating requirementQ* Heating requirement for hot water

supplresLosses from heating systemsPrimary energy requirementPrimary energy-related totalsystem cost index

2,6,49 Relationship between interior air temperature and surface temperature withrespect to the comfort of occupants [ 1 5]

30

28

Transmission

Q = Q n + Q , + Q ,

Q p = ( Q h + Q w ) . e p

26

Surface 24remperalure

22

20

1 8 .

t o a

1 t -

. "1a

1 o L1 2 20 22 24

Interior air temperature 'C26

2,6,50 Relationship between interior air temperature and relative humidity with respectto the comfort of occupants [ 1 6]

22 24 26

Interior air temperature u ("c )

2.6.51 Correction values AS for basic characteristic value S^ for solar heat oenetration

lnfluencing variables ito be considered As'Lightweight construction:timber studding, lightvveight panitions, suspended ceilingsExtremely li ghtwei ght construction:primarily internal insulation, large hall, few internal componentsSolar-control glassit with g < 0.4Increased night-time ventilation (night n > 1.5,h during 2nd half of night)Proportron of window area in facade > 65%Rooms facing north (NW-N-NE)Inclined windows (00-60" lo the horizontal)

- 0.03

- 0 . 1 0+ 0,04+ 0.03- 0.04+ 0 . 1 0- 0.06

178',

Climate-related moisture control

Climate-related moisture control

The effects of moisture caused by buildingwork, normal l iving conditions, rain and con-densation remain a problem in the constructionindustry. Therefore, measures have to be takento keep moisture of any kind away from thebuilding or reduce it to a safe minimum. Inade-quate moisture control decreases the level ofthermal insulation and can lead to later dam-age to the masonry through corrosion, frost,mould groMh and efflorescence. Figure 2.6.52ls a diagramn of the moisture loads on a build-ing.

From outside we have the effects of:. rain. snow. moist external air. moist soil, seepage water, a build-up ofwater, groundwater

From inside we have the effects of:' moisture from new building work. water in kitchens and bathrooms' dampness caused by the household, plantsand washing, and moisture evaporating fromthe occupants

. moisture condensing on the internal surfacesof components or within the components.

The physical'variables, symbols and units rele-vant to the assessment of moisture protectionare given in table 2.6.53.

Humidity

The air in the atmosphere always containswater vapour from the evaporatlon of water.Depending on the temperature, air can holdonly a certain amount of water vapour, and thisincreases as the temperature rises (see fig.2.6.54). As moist air cools, the dew point (orsaturation value) is reached. The saturationcontent of water vapour in the air correspondsto a saturation vapour pressure depending ontemperature. This also increases as the tem-perature rises to the same degree as thecapacity to hold water vapour.In the majority of cases the air contains slightlymore water vapour than the respective satura-tion content allows. The relative humidity Qserves to designate the water content of theair. This is the ratio between the actual amountof water vapour present W and the saturationquantity W" or the ratio between the prevailingwater vapour partial pressure p and the satura-tion pressure ps, given by

0 = W / V s = p / p s

For saturated air O = 1.0 or 100%. As moist airheats uo in a room without the addition orextraction of air, so the relative humidity dropsbecause the possible saturation quantity risesfor a constant quantity of water vapour. In thereverse situation - moist air cooling - the rela-tive humidity increases unti l the value of 100%,

i.e. saturation, is reached. lf the air cools fur-ther, the water must be separated out from theair, because the air at that temperature can nolonger hold that amount of water in vapourform. Mist forms in a gaseous atmosphere orcondensation on solid sudaces. The tempera-ture at which this process begins is known asthe dew point temperature, or simply dewooint. Constructional measures to avoid thetemperature falling below the dew point oninternal sudaces have been dealtwith in thesection "Thermal insulation" in coniunctionwith thermal bridges,

Hygroscopic moisture

Porous bodies absorb moisture in the form ofwater vapour from the surrounding air accord-ing to their physical and chemical properties.Adsorption may cause water molecules to col-lect on the surface of a material in one or morelayers, according to the relative humidity. Andin porous materials with a capil lary-l ike struc-ture, water can also accumulate on internalsurfaces. lf the water vapour in these capillar-ies condenses, the water moves according tothe laws of capillarity. This process is known ascapil lary condensation. These two mechanismscome under the general heading of "sorption".The hygroscopic properties of building mater-ials are described by sorption isotherms, whichorovide information on the moisture content ineach case depending on the relative humidity(see fig. 2.6.55). The temperature of the ambi-ent air has only a small influence. The hygro-scopic water content that becomes establishedunder normal ambient conditions is importantfor assessing moisture ratios in a material inpractice. The hygroscopic equil ibrium moisturecontents of various building materials are givenin table 2.6.23 (for reference climatic condi-tions of 23"C and 807o relative humidity).Besides the final values for sorption moisturewhich become established in the constantstate, the non-constant behaviour of surfacelayers is also interesting since they act asbuffer zones for f luctuating internal humidities.Kunzel [62] has shown that it is the propertiesof the outermost surface layers that are partic-ularly relevant for short{erm moisture changes,and that the substance of the wall beneathplaster or wallpaper no longer has any influ-ence. On the other hand, furnishings with ahigh textile content, e.g, upholstery, carpets,curtains etc., have a high sorption capacity,which means that no significant moisture fluc-tuations should be expected in l iving roomsand bedrooms, and the sorption behaviour ofbuilding materials is unimportant.

2.6.52 Moisture loads on external components

Driving rain

Surface water

Seepage water lDissolved salts

Water vapour partial PressureRelative humidityMass-related moisture contentWater vapour diff usion coeff icientWater vapour diffusion flow rateWater vapour diffusion resistanceWater vapour diffusion conductioncoefficientWater vapour diffusionresistance indexWater absorption coeff icientWater vapour diffusion-equivalent air layer thicknessArea-relatedcondensation massArea-relatedevaporataon mass

Vapour ditfusion

p@u

Dsz

6

1kg/kgm2hkg/m'?hm'?hPa,rkg

kg/mh Pa

! r lw kg/m2 ho 5

s d m

flw,r kg/m2

flwv kg/m2

2.6,54 Water saturation or dew point graph

trt c

6

o

co l nC

o

o

= s

2.6.53 Variables, symbols and units used in moisture

Building science

-b

! r (

Coco 1 no -ol

> c

2.6,55 Ranges of sorption curves

Relative humidity (%)

Clay bricks, gypsumNormal-wei ght concrete, li ghtwei ght concrete, auto-claved aerated concrete, calcium silicateTimber, organic fibrous materials

2,6.56 Capillary water absorption of various buildingmaterials in relation to the square root of thetime (after KLinzel)

Capillarity

In water-filled pores and tube-like materialstructures in building materials, capil lary ten-sile forces occur due to the surface tension ofwater, depending on the concave radius of themeniscus and the wettability of the solid mater-ial. The capil lary suction can have either a pos-it ive or negative effect on the building, depend-ing on the moisture load and the associatedmoisture movement. The absorption of waterand conveyance by capil lary action due to dri-ving rain or moist soii must be avoided. On theother hand, the capil larity of a building materialpromotes the transport of water from within abuilding component to the surface, where itthen has the chance to evaporate. This accel-erates the removal of moisture from the build-ing process from masonry. In the case of con-densation forming within the masonry due towater vapour diffusion, the amount of conden-sation can be reduced by capillary action andthe chance to dry out improved. A standard-ized test in DIN EN ISO 15148 is suitable forestablishing the water absorption of a capillary-type porous material. In this test a sample sur-face is immersed in water and the increase inmass determined as a function of the absoro-tion time. The water absorption increases lin-early in proportion to the square root of theimmersion time (see fig. 2.6.56). The curvecorresponds to the water absorption coefficientspecific to the material:

W = w x r f

where:W = the quantity of water absorbed for a unit

surface areainkg/m2t = the absorption time in hw = the water absorption coefficient in

kg/m2h{ 5

Table 2.6.58 gives w-values for materials typic-ally used for building walls.

Water vapour diffusion

in physical terms, air is a mixture of gases inwhich the nitrogen, oxygen and water vapourmolecules circulate independently. Each indi-vidual gas exerts the same partial pressure itwould exert at the same temoerature if theother gases were not present. Existing mois-ture differences in tvvo blocks of air are bal-anced by water vapour diffusion in the direc-tion of the potential gradient. This diffusionshould not be confused with a flow whichoccurs as a result of a total pressure differ-ence. In diffusion processes, the same totalpressure is generally present on both sides ofa separating layer. The external components ofheated interiors are subjected to water vapourdiffusion processes because they separateblocks of air with different temperatures andmoisture contents. The diffusion orocess with-

out occurrence of condensation is easily i l lus-trated for a single-layer component (see fig.2.6.57). The water vapour diffusion flow rate gin kg/m'zh through a component in the constantstate is calculated using the equation below.To do this, we must know the water vapour par-tial pressures p; and p" in Pa on both sides ofthe component as well as the water vapourdiffusion resistance Z of the component. At areference temperature of 10"C, Z can becalculated from

Z = 1 . 5 x l 0 6 x p x d

Consequently, the diffusion flow rate is indirect-ly proportional to the diffusion resistance gen-erally applicable and the thickness of the build-ing material. The dimensionless material prop-erty p specifies by how much the diffusionresistance of a material is greater than the sta-tionary air. The ;r-value of air is therefore 1. Asthe thickness is of course important for calcu-lating the diffusion resistance of a componentor layer of a component, in practice we use thediffusion-equivalent air layer thickness

s o = p x d

This unit is specified in m. In some cases thischaracterizes the diffusion properties of abuilding material layer better than the p-valueon its own. This is particularly true for thin lay-ers and vapour barriers (see table 2.6.59). Thediffusion-equivalent air layer thicknesses of thinlayers have recently been defined in DIN 4108oart 3 as follows:

- open diffusion layer with sd < 0.5 m- diffusion-resistant layer with

0.5 m < so < 1500 m- closed diffusion layer with so > 1500 m.

Water vapour diffusion resistances for buildingmaterials and masonry are specified in DIN4'108 oart 4 and DIN EN 12524. Two values aregiven in DIN 4108 part 4 in order to takeaccount of the scatter for type of material ortype of masonry. In calculating the diffusion,the less favourable water vapour diffusionresistance should always be used for the con-densing period. This means that when conden-sation occurs within a type of structure, thelower p-values should be used for calculatingthe quantity of condensation on the inner(warm) side of the condensation.plane or con-densation zone, and the higher p-values for theouter (cold) side. However, the values used forcalculating the mass of condensation shouldbe retained for calculating the evaporationoptions. Table 2.6.60 provides an overview ofthe water vapour diffusion resistances formasonry and plaster given in DIN 4108 part 4.In contrast, the European standard DIN EN12524 distinguishes between water vapour dif-fusion resistances determined accordinq to the

B

c

Fo

E,ub.

€ r o6 -

o63 s

, / , ,

t/3

4

t/ -'t-

5

t/u*0 1 2 3 4 5

1: Gypsum 1390 kg/m32: Solid clay bricks 1730 kg/m33: Autoclaved aerated concrete 640 kg/m34: Calcium silicate 1780 kg/m35: Pumice concrete 880 kg/m3

6 7 8 I 1 0

Time (h)

2.6.57 Waler vapour transport through an external com-ponenta temperature gradientp Water vapour partial pressure gradient

0

180

Climate-related moisture control

dry and moist zone method of DIN EN ISO12572. ln the first case the material is essen-tially dry during the test because the humiditieson both sides of the sample are approx. 0%and 50%, but in the second case about 50%and 95%, so that for hygroscopic materials anappropriaie moisture content becomes estab-lished and influences the p-value through thetransport of the sorbed water (see fig. 2.6.61).Conesponding figures for building materialscan be found in table 2.6.62. lt can be seenthat the ;r-values for the moist zone with thegreater flow of sorbed water are lower thanthose for the dry zone.

Calculating the quantity of condensation within

components

The quantity of condensation accumulatingwithin a component and the chance of dryingout can only be estimated and not accuratelycalculated owing to the assumptions concern-ing the climatic boundary conditions and thewide scatter of material parameters. Even sub-sequent calculations, carried out within thescope of assessing damage, are fraught withuncertainties. The water vaoour diffusion resis-tance is the most important material propertybut can varyconsiderably in practice due toutilization effects. In the case of hygroscopicmaterials the water vaoour diffusion is con-cealed by sorption processes and flows ofadsorbate films.Several methods - with different claims toaccuracy - are known for investigating the pos-sible saturation of components by the forma-tion of condensation, which results from the dif-ference between the amount of water accumu-lating and the amount able to dry out. TheGlaser method is covered by a standard. Thisis a simple graphic method for estimating pos-sible moisture bleeding within the cross-sec-tion of a wall and the possible drying-outbased on a constant state for the temperaturezone and the vapour partial pressure gradient.With constant climatic conditions for the con-densing period over two winter months and theevaporating period over three summer months,we also speak of the block method. Figure2.6.63 is a schematic presentation of a simplediffusion diagram with a condensation planebetween layers 2 and 3, as would be the case,for example, in a twin-leaf masonry wall wlthcavity insulation. However, owing to the misun-derstandings which often occur in practice, itmust be emphasized that the DIN method is anestimate of the accumulation of condensationand its possible drying-out as well as a check -proved over decades - of the absolute safetyof a component subjected to standard condi-tions. The climatic boundary conditions and themethod of analysis are described in detail inDIN 4108 part 3. The basic requirement is thatthe formation of condensation within compo-nents, which leads to damage or impairment of

solidvertically perforated

normal-weighl solid calcium silicatelightweight concrete solid calcium siiicate

pumice concretepumice concreteautoclaved aerated concrete

2.6.58 Water absorption coefficient of building materials (after Kunael)Mate{bl Gross density Water absorption

2.98 ,3

vertrcally perforated 11e 1635 7 '7

autoclaved aerated concrete 600autoclaved aerated ooncrete 630normal-weight concrete 2290normal-weiqht concrete

17601920

a l q

1 085535

5.53.22.91 . 94.04.2

1 , 81 . 1

2.6.59 Water vapour diffusion-equivalent air layer thickness to DIN EN 12524 of thin layersProducvmaterial water vapour

diffusion-equivalentair laYer thickness

Dd

m

2410

5010050301500821 0o,20.132

Note: The water vapour diffusion-equivalent air layer of a product is specified as the of a stationary

layer of air with the same water vapour diffusion resistance as the product. The thickness of the product in the table is

not normally measured and can be related to thin products with a water vapour diffusion resistance. The table speci-

fies nominal thickness values as an aid to identifying the product

Polyethylene 0.15 mmPolyethylene 0.25 mmPolyester sheet 0.2 mmPVC sheetAluminium fo i l 0.05 mmPolyethylene sheet (stacked) 0,15 mmBitumenized paper 0.1 mmAluminium composite foil 0,4 mmRoofing felt for wallsCoating materialHigh-gloss lacquer

2.6.60 Recommended values for diffusion resistance indexes to DIN 4108 paft 4; upper and lower limits of materialscatter

Material Recommended value for watervapour diff usion resista!eelnqell0l)

PlastersPlastering mixes of lime, lime-cemenland hydraulic limePlastering mixes of lime-gypsum, gypsum, anhydrite and lime hydrite 10Lightweight plasters 15/20Gypsum plasters 10Thermal insulation plaster 5/20svnthetic resin Dlaster 5o/2oo

I 5/35

coefficient

Masonry ofsolid engineering bricks, vertically per{orated engineering brickshigh-strength engineering brickssolid clay bricks, vertically perforated clay brickslightweight vertically perforated clay brickscalcium silicate, gross density 1.0-1 ,4calcium silicate, gross density 1.6-2,2granulated slag aggregate unitsautoclaved aerated concretelightweight concrete 5/10

50/1 Qo

5/10

5/1015/2570/1005/10

181

Building science

2.6.61 Diagram of direction of diffusion upon measur- the function due to the increase in moistureing the water vapour permeability in the dry and contained in building and insulating materials,moist zones, and specification of the water con-tent in the samptes and sorbate water transDoft should be avoided. This is generally the casefor a hygroscopic material with the given sorp- when the following conditions are satisfied:tion curve (after K0nzel) . Building materials that come into contact with

condensation should not suffer any damage

5 0 % | 5 0 % ^ . ( e , g . t h r o u g h c o r r o s i o n , m o u | d g r o w t h ) 'I

- 1

' Water accumulating within the component

I I I e3l

t I ] during the condensing period must be able to/ f i escape to the surroundings again during the

3olo ^' I " uo:/

) e3%

| evaporating period.( ) , 1 t I I

&. g l f | __,_ l .Thearea-re latedquant i tyofcondensat ion

Sorption moisture Sorbate water Sorption moistureIn sampte transport in sample

2.6.62 Water vapour diffusion resistance indices for thedry and moist zones to DIN EN 12524

Material Water vapour diffusonresistance indexpdry moist

Plastering mix 20 10

should not exceed 1.0 kg/m, for roof and wallconstructions.

' lf condensation occurs at the contact faces ofcapil lary, non-absorbent layers, the permis-sible condensation mass may be reduced to0.5 kg/m2; provisions covering timber com-ponents are given in DIN 68800 part 2.

'An increase in the mass-related moisturecontent u exceeding 5% is not permitted fortimber (3% for timber derivatives); wood-wooland multi-ply l ightweight building boards toDIN 1 101 are excluded from this.

ln contrast to the DIN method, Ihe Jenischmethod lakes into account the temoeraturerelationships at the location of the building[90]. This makes use of the mean annual f igureand the frequency of the daily average for theexternal air temperature in certain climaticzones in order to establish whether the mass ofcondensation occurring in a component candry out again during one year, This method isslightly more involved than the DIN method butsupplies a more accurate annual balance forthe occurrence of condensation and thechance of it drying out.The COND method l72l enables a moistureprofi le in multi- layer enclosing constructions tobe calculated on the basis of the coupled heat,water vapour and capillary water transport, andhence forms a solid foundation for - in terms ofmoisture - a correct and differentiatedapproach to the physics of the building struc-ture. Starting with a simple block climate forwinter and summer, similar to DIN 4108 part 3,the capil larity and hygroscopicity of the build-ing material are taken into account in additionto the water vapour diffusion, As the cold sea-son begins, the difference between watervapour quantities diffusing into and out of thematerial, initially without formation of condensa-tion, is used to create a hygroscopic load with-in the component. Once the water vapour satu-ration pressure is finally reached, condensationdoes form but, at the same time, capil lary reliefbegins. The balance of vapour and capil larywater flows leads to a reduced moisture loadcompared to the pure diffusion method. Duringthe warm part of the year the. material isrelieved by water vapour and capillary watertransport - until the condensation has driedout. Finally, further drying takes place unti lhygroscopic moisture content equilibrium with

the surrounding air is achieved.Moisture transport in components taking intoaccount sorption, diffusion and capillarity effectssubjected to non-constant climatic conditions isreflected inthe KieBl method[94]. The asso.ciated computer program'WUFI' [219] takesinto account the conditions of the temperatureand relative humidity of the internal and exter-nal air as well as the rain load and the radiationloss according to the inclination and orientationof the component. This information can be ob-tained from measured weather data or fromtest reference years, Material data such asporosity, specific heat capacity, thermal con-ductivity, diffusion resistance, moisture storagefunction and fluid transport coefficient are allput into the calculation. The computer programthen determines the chronological progressionof the temoerature and moisture zone withinthe component.

Moisture behaviour of masonry

DIN 4108 paft 3 describes components that, inthe light of experience, can be regarded asabsolutely safe with respect to saturation, andfor which a'mathematical analysis of conden-sation is not required. The condition for this isadeouate minimum thermal insulation accord-ing to DIN 4108 part 2 and normal interior clim-ates. Figure 2.6.64 provides an overview ofexternal wall constructions which are absolute-ly safe in terms of the formation of condensa-tion internally.

The masonry walls are made up as follows:

. Single-leaf masonry to DIN 1053 part 1 andwalls of autoclaved aerated concrete toDIN 4223 with internal olaster and thefollowing external layers:- rendering to DIN 18550 part 1- claddings to DIN 18515 parts 1 and 2attached by mortar or bonding with a jointproportion of at least 5%- ventilated external wall claddings toDIN 18516 part 1 with and withoutthermalinsulation- external insulation to DIN 1 102 orDIN 18550 part 3 or an approved thermalinsulation composite system

. Twin-leaf masonry to DIN 1053 part 1 , alsowith cavity insulation

. Walls of masonry with internal insulation sub-ject to the following limitations:- internal insulation with a thermal resistanceof the thermal insulation layer R < 1.0 m2KAiVas well as a value for the water vapour diffu-sion-equivalent air iayer thickness of thethermal insulation layer with internal plasteror internal cladding sdi > 0.5 m- internal insulation of plaster or clad wood-

wool l ightweight building boards to DIN 1 101with R < 0.5 m2KAlVwithout any fudherrequirement for the so,-value

Clay brickCalcium silicateConcrete with expandedefAV Adf lrAnrlcc 6 4

Concrete with lightweightaggregates 15 10Autoclaved aerated concrete 10 6

1 6 1 020 15

2.6.63

Diffusion diagram for condensation case

All

t z J

Water vapour diffusion with condensationoccurring in one plane of the buildingcomponent

'ut z o

D . - O^ | s wu i =

7 t

Diffusion diagram for evaporation case

't82

p - p ,. S W I

4

D - O' s w e

4

Climate-related moisture control

. External basement walls of single-leaf mason-ry to DIN '1053 part 1 or concrete to DIN 1045with external thermal insulation.

These provisions in the standards are basedon many years of experience and, as a rule, l ieon the safe side. lf a construction deviates fromthe details given in the catalogues, this doesnot necessarily mean that the construction willfail, A number of selected investigations ofexternal walls show the serviceability of facadecladdings with Iimited ventilation, the use ofvarious combinations of materials for twin-leafmasonry with cavity insulation and the absenceof problems - in terms of moisture protection -with internal insulation. The wall protected byan external cladding, with or without additionalthermal insulation, is a proven form of wall con-struction. The transport of moisture from thewall to the outside is achieved as shown in fig.2.6.65 by ventilation to the rear of the claddingin conjunction with the formation of conden-sation on the inner face of the cladding, whichthen drains away. The mechanism whichapplies depends on the degree of venti lation.Tile-like, small-format elements also benefitfrom a considerable moisture exchange byway of the perviousness of the cladding [131 ].Therefore, if a cladding is not ventilatedaccording to DIN 18516, this does not repre-sent a defect, provided the condensation onthe rear face of the cladding can drain awayand does not lead to damage to the load-bearing construction [1 30].ln a full-fill cavity wall, thermal insulation mater-ials with any water vapour permeability can becombined with all relevant building materialsfor the inner leaf and an outer leaf of clay orcalcium sil icate facing bricks l5l.When calculating the diffusion according toDIN 4108 part 3, the amount of condensationaccording to figure 2.6.66 l ies below themaximum oermissible condensation mass of1000 g/m'z, even for the most unfavourablecase of thermal insulation open to diffusion(e.9. mineral wool, loose insulation) and a thininner leaf. Only for an outer leaf of engineeringbricks must water occurring within the compo-nent during the condensing period be able toescape again to the surroundings during theevaporating period (m*:m* < 1) not fulf i l led -on paper - for insulating materials open to dif-fusion (see fig. 2.6.67). Taking lnto accountlaboratory tests on samples of wall in aMunich-based thermal insulation research cen-tre, further practical investigations [53] and thefact that the condensation that occurs is only afraction of the amount of driving rain that pene-Vates an outer leaf, a full{ill cavity wall can beregarded as absolutely safe, even when usingengineering bricks, with respect to the forma-tion of condensation within the wall.Practical studies of the formation of condensa-tion within comoonents with internal insulationhave been carried out on common forms of

Single-leaf walls: monolithic, with ventilated cladding, with thermal insulationcomDosite svstem

Twin{eaf walls: with cavity, with partialJill cavity, with full-fill cavity

Single-leaf wall withinternal insulation

I l . R<1.0 m2 k. r - w

156; 2 0.5 m

Basement wall withexternal insulalion

halve the thermal transmittance values oftenencountered in old buildings. A diffusionresistance U = 5 allows the construction toremain open to diffusion. Possible conden-sation behind the insulation is dispersed andrelieved by the high capil lary action so thatdiffusion-resistant layers are unnecessary.Apart from that, the pH value of calcium sili-cate makes it resistant to mould growth andits hygroscopicity is a help in regulating theinternal climate, i.e. moisture load peaks inthe interior are buffered.

2,6.64 biternal masonry walls for which a mathematical analysis of condensation is not necessary

r-t l

-tIrEErfl

EEEE

-tlEEEElt

masonry with different types of internal insula-tion in laboratory tests under the climatic con-ditions according to DIN 4108 part 3 [a].Masonry walls made from no{ines l ightweightconcrete, calcium sil icate and clay bricks withdiffusion-permeable insulating materials suchas mineral fibres, even those without vapourbarrier, are absolutely safe with respect to sat-uration in winter. The thermal insulationremains dry during the condensing period.However, the increase in the water content ofthe masonry exceeds the limit of 1.0 kglm'zaccording to DIN 4108 part 3. The necessarydrying-out during the evaporating period isachieved. Theoretical studies with a constantinternal climate and practical external climate[95] confirm this assumption for certain typesof masonry. As in the laboratory tests, theyproduce higher moisture fluctuations in themasonry compared with the use of denserinsulation materials or vapour barriers. Buttjoints near the covering on the inner face inconjunction with rigid expanded foams or min-eral fibre boards, with vapour barriers interrupt-ed at the butt joints, have no measurable effecton the water content of the masonry. Investiga-tions carried out on existing structures confirmthe laboratory measurements, Insulating ma-terials with active capil laries, e.g. calcium sil i-cate, have recently been favoured for the inter-nal insulation of buildings with facades worthpreserving [73]. A thickness of just 40 mm can

183

Building science

2.6.65 Schematic presentation of moisture loss in ex-ternal walls with claddings. With ideal ventilation(O" = 4),the wall moisture is carried away withthe air (right). With less than ideal or no ventila-tion (Oa < O,), some moisture diffusing out of thewall can condense and drain away (left) [7]

2.6.66 Condensation mass mwr in relation to diffusion-equivalent air layer thickness of inner leafThermal insulation layer: mineral fibre boardsOuter leaf: clay facing bricks

.\--:___=-=-

0 . 5 1 . 0 1 . 5 mDiffusion-equivalent air layer thickness

0.1 0 .2Thickness of inner leaf

0.3 m (u=5)

Water vapour convection

Walls and roofs must be airtight to prevent thethrough-flow and convection of internal humidi-ty, which can lead to the formation of conden-sation. Special attention should be paid to theairtightness of junctions with other componentsand service penetrations. Transverse flows inventilation layers within a construction betweenrooms heated to different temperatures shouldalso be avoided. Facing masonry and timberframes, as well as masonry to DIN 1053 part 1 ,are not airtight without further treatment. Thesetypes of walls must be given a coat of plasterto DIN 18550 part 2 on one side or made air-tight by other suitable measures. Plasters toD lN 1 8550 DarL 2 or 1 B55B are classed as air-t ight layers.

Protection against driving rain

Driving rain loads on walls are caused by thesimultaneous effect of rain and wind blowingagainst the facade. The rainwater can beabsorbed by the wall by way of the capillaryaction of the surface or enter via cracks, gapsor defective seals as a result of the oressurebuild-up. lt must be ensured that the waterentering the construction can escape again tothe outside air, Providing a wall with proteciionagainst driving rain in order to l imit the absorp-tion of water by capillary action and to guaran-tee evaporation opportunities can be achievedthrough constructional measures (e.9. externalcladding, twin-leaf masonry) or through render-ing or coatings. The measures to be takendepend on the intensity of the driving rain load,which is determined by the direction of thewind and the level of precipitation as well asthe local situation and type of building. Accord-ingly, three loading groups are defined in DIN4108 part 3 in order to assess the behaviour ofexternal walls subjected to driving rain. A rain-fall map of Germany provides general informa-tion about precipitation levels. However, this isonly the starting point for assessing driving rainbecause the local circumstances, alt itude andform of the building (roof overhang, height ofbuilding) must also be taken into account (seefig. 2.6.68). Therefore, the loading groups forGermany are defined with associated explana-tions:

Loading group I - low driving rain loadAs a rule, this loading group applies to regionswith annual precipitation levels < 600 mm butalso to locations well protected from the windin regions with higher levels of precipitation.

Loadlng group ll - moderate driving rain loadAs a rule, this loading group applies to regionswith annual orecipitation levels of 600-800 mmas well as to locations well protected from thewind in regions with higher levels of precipita-tion and to tall bulldings or buildings in exposedpositions in regions where the local rain and

wind conditions would otherwise cause them tobe allocated to the low driving rain loading group.

Loading group lll - high driving rain loadAs a rule, this loading group applies to regionswith annual precipitation levels > 800 mm or towindy regions, even those with lower levels ofprecipitation (e.9. coastal areas, hil ly andmountainous regions, the foothil ls of the Alps),as well as to tall buildings or buildings inexposed positions in regions where the localrain and wind conditions would otherwisecause them to be allocated to the moderatedriving rain loading group.

External walls with rain protection provided byrendering or coatings are assessed using thewater absorption coefficient w for waterabsorption during rai,nfall and the diffusion.equivalent air layer thickness sd of the layerproviding rain protection for the loss of waterduring dry periods [106]. In order to l imit theshort{erm increase in moisture during rainfall,the water absorotion coefficient should notexceed a certain value, even when drying-outis guaranteed in the long term. The lower thediffusion-equivalent air layer thickness sd of thesurface layer, the more quickly the componentloses water - which entered during driving rain- in the dry period. So such a surface layershould be water-resistant or water-repellentwith respect to rain protection, but at the sametime remain as permeable as possible forwater vaoour to allow the moisture which haspenetrated to escape quickly. The require-ments for rain protection provided by renderingand coatings are defined in DIN 4108 part 3(see table 2.6.69).The rain orotection is confined to the outer leafin the case of twin-leaf walls with an air spaceor masonry with a ventilated cladding. Aittight-ness and thermal insulation are the tasks of thejnner leaf. ln a full-f i l l cavity wall, the cavityinsulation should not impair the resistance todriving rain, and moisture should not be able toreach the inner leaf via the insulation. The cavi-ty insulation must be covered by a standard,otherwise its serviceability will have to be veri-f ied in accordance with building authority regu-lations. Loose materials and mineral fibreboards must possess hydrophobic propertiesto repel the water. An overlapping steppedjoint is adequate for plastic foams in order toguarantee that the water drains to the base ofthe wall. lf loose cavity insulation materials areemployed, suitable measures must be taken atthe openings at the base of the external leaf inorder to prevent material from escaping. Aswith a cavity wall, a damp proof course mustbe provided at the base and above all open-ings together with weep holes to allow drivingrain which has penetrated the outer leaf todrain away.When using thermal insulation composite sys-tems, cracks in the rendering could endanger

,$i

m 800

ing/m'

600,llI 400

200

184

Climate-related moisture control

the driving rain protection and impair the ther-mal insulation mainly provided by the externalthermal insulation layer, The effects of cracksin rendering have been investigated on exter-nal walls subjected to natural weather condi-tions at the open-air test centre of the Fraun-hofer Institute for Building Physics [14]. Afterthree year,s of exposure to the weather, it cangenerally be said that for rendering on rigidexpanded polystyrene and polyurethane foamsheets as well as hydrophobic mineral f ibreboards, cracks with a width of approx. 0.2 mmdo not impair the function of the rendering asrain protection to any significant extent, pro-vided the substrate does not conduct throughcapillary action or is water-resistant. As asimple planning aid, DIN 4108 part 3 givesexamples of the classification of standardtypes of wall according to the three loadinggroups (see 2.6.70). However, this does notrule out the use of other types of constructionproved by years of practical experience.

2.6.67 Drying-out oppodunities in relation to the diffu-sion-equivalent air layer thickness of insulationmaterial when using outer leaves of clay facingbricks and engineering bricks

Engineer ing

Xi"to'

--{1----I bricks

requirement coefficient

2.6.68 Allocation of driving rain groups according toposition and form of building

m*/m*

t12I

l"0.8

0.6

o.4

0.2

air layer thicknesssd

w x s dkg/m6o s

2,6.70 Examples of the allocation of standard wall types and loading groups according to DIN 4108 part 3Loading group I Loading group ll Loading group llllow driving rain load moderate driving rain load high driving rain loadRendering to DIN 18550 pt 1without special requirementsfor driving rainprotection. External walls of masonry,wall panels, concrete or similar. Wood-wool lightweightboards (with reinforced joints). Multi-ply lightweight boards(reinforced over entire surface)t o D I N 1 1 0 1 ,instal led according to DIN 1102

Water-resistant renderin gto DIN 18550 pt 1 on

Water-repellent rendering toDIN 18550 pts 1-4 or synthetic resinplaster to DIN 18550 on

. External walls of masonry, wall panels, concrete or similar'Wood-wool and multi-ply lightweight boardsto DIN 1101, insta l led according to DIN 1102

;r;lE3E

____-,,"i< :l:l l E f i i t t * t t t

Diffusion.equivalent air layer thicknessu x s of insulation material

2.6.69 Requirements for rain protection to rendering and coatings according to DIN 4108 part 3 - -Diffusion-equivalent

- Product

< w < 2 . 0

leafto DIN 1053 ot 1. 310 mm thick to(wjth internal plasteo

aoolied in thick- or thin-bed mortar

(with internal plaster)

Externat walls with tiles or pan"

pt 1, 375 mm thickTwin-lealto DIN 1053 pt 1 with partial-or full-fill cavity

to DIN 18515 pt 1 appl iedin water-repellent mortar

External walls with dense microstructure outer laver of concrete to DIN 1 045 and DIN 1045 pt 1 (draft) asDIN 4219 pts 1 &

with ventilated e)dernal to DIN 18516 ots 1, 3 & 4with external insulation by means of a thermal insulation plaster system to 1 8550 pt 3 or an approved

thermal insulationExternal walls in timber with weatherNote: Drained ioints between

tion 8.2 of DIN 68800 pt 2

185

Building science

2.6.71 Sound levels of various sources

Jet engine (at 25 m) -

D^^ ^ r^ ' ' ^I v v v , u u v -

Heavy goods traffic -

Conversation ;

Library -

Bedroom >

1 1 0

100 <-- Pneumatic drill

90

,..- Average traffic6U

70

- OfficeOU

50

40 < Living room

30

20< Forest

1 0

0 Llmi t of audibi l i ty

Excitation of structure-borne sound

Sound insulation

Sound insulation is becoming more and moreimportant throughout the building industry. Thisprimarily concerns questions relating to thehealth and well-being of people. Sound insu-lation is particularly important in housing be-cause this is where oeople relax and rest andneed to be shielded from the everyday noisesof their neighbours. And sound insulation is anindispensable part of the building system ifschools, hospitals and offices are to be usedproperly. Sound insulation in buildings beginsat the design stage. For instance, noise-sensitive rooms like bedrooms and livingrooms should be placed within the plan layoutso that they are unlikely to be affected byunacceptable external noise; a useful expedi-ent is to group those rooms with similar func-tions together. Besides careful planning, soundinsulation measures can only be successfulwhen great care is exercised during construc-tion, Even minor flaws in workmanship can leadto, for example, acoustic bridges for structure-borne noise, which then practically null ify theentire sound insulation measures. Putting rightsuch problems subsequently is in many casesimpossible or at best extremely expensive.

Terms and definitions

Sound insulation is the protection againstsound which is conveyed in various ways(see fig, 2.6.72):

. Airborne sound is sound which propagates inair (a gaseous medium). Upon striking a solidbody (building component), partof the airborne sound is reflected and part isabsorbed or attenuated.

' Structure-borne sound is sound which propa:gates in solid materials. In buildings these arefrequently noises caused by building servicesand machinery which are then conveyed viathe construction.

. lmpact sound is a special form of structure-borne sound caused by people walkingacross the floor.

Sound is the mechanical vibration of an elasticmedium whose frequency l ies within the audi-ble range of the human ear (between 16 and20 000 Hz). Frequency f is defined as the num-ber of vibrations per second. As the frequencyincreases the pitch rises. A doubling of the fre-quency corresponds to one octave. In buildingacoustics we are generally concerned with arange of f ive octaves - from 100 to 3150 Hz(see fig. 2.6.73). The periodic sound vibrationgenerates an alternating pressure in air or f lu-ids known as sound pressure p. The soundpressure is superimposed on the static pres-sure present in the respective medium and canbe measured by using a microphone.The sound pressure level L describes sound

Sound leveldB(A)

140

130

120

Jet aircraft taking off(at 100 m)

2.6.72 Airborne and structure-borne sound

Excitation of airborne sound

2.6.73 Frequency ranges

Infrasound Audible range

*)),),

186

Ultrasound

R r r i l r l i n n a a n r r e + i n c

Speech -----?

Sound insulation

events in building acoustics. As the human earis in a position to perceive a range equal to 1 x106, the sound pressure level (often abbreviat-ed to SPL) is described using a logarithmicscale, This is the base 10 logarithm of the ratioof the square of the respective sound pressurep to the square of the reference sound pres-sure po:

L = 10 log,o (p'/po')

The unit of sound oressure or sound level dif-ference is the decibel (dB). The sound level isspecified using the A-scale dB(A); this is basedon the A-weighting network, which approxi-mates to a scale of volume comoarable to thatof the sensitivity of the human ear. A sound thatincreases by 10 dB is perceived to be twice asloud, The sound level extends from the l imit ofaudibil i ty 0 dB(A) to the pain threshold . A num-ber of typical sound levels are given in fig.2.6.71. So sound insulation means reducing thesound levels of sound sources to an accept-able level when they cannot be diminished.The sound reduction index R describes theinsulating effect of components against air-borne sound. This is calculated from the soundlevel difference befuueen hryo rooms (sourceand receiving rooms) taking into account theabsorption surface A of the receiving room andthe test surface of the comoonent S:

R = ! - L r + 1 0 t o g , o ( S / A )

fhe airborne sound insulation rndex R* is asingle value for the simple identif ication ofbuilding components. As shown infig.2.6.74,a curve B, the shape of which takes intoaccount the sensitivity of the human ear, abovethe l ine of measured frequencies M, is dis-placed downwards in steos of 1 dB unti l theaverage undershoot U of the displaced gradecurve below the measured curve is max. 2 dB.The sound reduction index of the displacedgrade curve at 500 Hz is taken as the singleidentifying value.In practice the airborne sound insulation indexis specified taking into account the soundtransmission via flanking components (see fig.2.6.75). Flanking transmission is that part of theairborne sound transmission between two ad-jacent rooms which does not take place direct-ly via the separating component but instead viaauxil iary paths through adjoinin g components.lmpact sound is structure-borne sound gener-ated by walking or similar excitation of f loors orstairs, and is transmitted to the rooms belowpartly directly as airborne sound or via flankingcomponents as structure-borne sound waves,lmpact sound insuiation is usually improved bya two-layer arrangement in the form of the floorfinish being supported by a "floating" construc-tion on the structural f loor.A floating screed is a supporting layer which isseparated from the structural floor, and from

the walls on all sides as well as door framesand service penetrations, by a resil ient insulat-Ing layer.

Requirements

Minimum reouirements for sound insulationhave been laid down in a number of construc-tion law documents. DIN 4109 specifiesrequirements for airborne and impact soundinsulation befureen individual functional units inbuildings and requirements for protectionagainst external noise. lt should be noted herethat the requirements apply only to the soundperformance of separatin g componentsbefuueen different residential or office premis-es; there are no minimum requirements forsound insulation within residential or officepremises. Supplement 1 to DIN 4109 (exam-ples of details and methods of calculation) hasbeen implemented by the building authorit ies.Supplement 2 to DIN 41 09 (recommendationsfor enhanced sound insulation and sugges-tions for sound insulation within oremises) hasnot been implemented by the building authori-t ies, and necessitates a special agreementbetween developer and architect. Bearing inmind the increasing quality awareness ofusers, the designer should check whether theenhanced sound insulation measures of sup-plement 2 can be implemented taking intoaccount technical and economic aspects. Aguide to the contents of DIN 4109 and the sup-plements is given in fig. 2.6.76. Work on Euro-pean standardization is being carried out bythe technical committee CEN/TC 126 "Acousticproperties of building products and of build-ings" .The European standard is essentially con-cerned with the harmonization of testing meth-ods (laboratory and in situ), the evaluation oftest results and the drawing-up of methods ofcalculation for determining the acoustic perJor-mance of buildings based on the properties oftheir components. The standards being pro-duced for this by CEN will have a direct influ-ence on the provisions of DIN 4109. The Ger-man building acoustics standardization con-cept wil l have to undergo a fundamental over-haul. The DIN study groups responsible arecurrently working on a standardization conceptthat takes the harmonized codes into account.Both DIN 4109 and suoolement 1 wil l need tobe revised.The work to be carried out essentiallv involvesthe following areas:

' A revision of DIN 4109 while retaining the cur-rent level of reouirements.

. The production of a building componentcatalogue.

. The integration of the harmonized method ofcalculation in the German building acousticsconcept, including the drawing-up of instruc-tions.

2.6.74 Example of formation of average value with theaid of the evaluation curve

0100 204

authoritiesDIN 4109 Yes Protection of occupied

rooms against. noises from rooms notbelonging to the samepremises. noises from buildingservices and operationson the same premises. external noise and thenoise of commercial or

Supplement 1 Yesto DIN 4109

Examples of constructiondetails and methods ofcalculation

Supptement Z t lo Advice on design andconstruction andrecommendations forenhanced sound insulation

400 800 1600 3200 rzFrequencY f

1) LSM = alrborne sound nsulation margin

2.6.75 Transmission paths for airborne sound

Besides transmlssion through the separating wall (path 1 ),the alrborne sound is also transmitted via paths 2,3 and 4

2.6.76 Requirements and recommendations for soundinsulation

Designation lmplemented Contenlby bui ld ing

c d Bo

c. E

5 5 0F

lco

! l oc - "lo

Displaced

Flanking transmission

to DIN 4109

187

Building science

2.6.77 Aibo"ne sound insulation for walls and doors to prevent sound transmission from otherresidential or working areas _.__

Componenl Fequirementsto D IN 4109 r )

1. Multistorey buildings with apartments and work roomsParty walls betlveen apartments and walls betureen separateworK premrsesStaircase walls and walls adjacent to communal corridorsWalls adjacent to driveways, entrances to common garages etc.Walls to games or similar community roomsDoors' which lead from communal corridors or stairs to corridors andhallways in apartments and residential homes or from work rooms;. which lead from communal corridors or stairs directly

ronr l P'

dB

Recommendationsfor enhancedsound insulation

cr rnn lomon+ ?z l

r ^ ^ d R '

dB

53523j5555

> 5 5> 5 5

> 3 727

rooms - corridors and 372. Semidetached or terraced housesPartv walls 57 > 6 73. Hotels etc.Walls betvveen. oeorooms. corridors and bedroomsDoors

4747

a c > 3 7

The necessary work wil l involve masonry andreinforced concrete, steel and other frames,timber construction, elements (windows, doorsetc.) and building services.In Germany, supplement 3 to DIN 4109 hasbeen prepared for the transition period. Thiscontains a method for converting the airbornesound insulation index R* determined in thelaboratory without f lanking transmission into avalue R'w, which is sti l l required at present forthe German system. The reverse procedure,i.e. converting R'* to R*, is also included in thesu00lement .The level of requirements for sound insulationin buildings is not affected by the Europeanstandard, The establishment of requirementsremains exclusively the province of nationalbodies and can therefore be adjusted to therespective national traditions and develop-ments rn the construction industry, According-ly, DIN 4109 is not threatened in this respectby developments at European level.

Sound insulation against internal noise

f able 2.6.77 l ists the requirements of DIN 4109and the recommendations of supplement 2 toDIN 4109 for a number of selected walls forprotecting occupied rooms against soundtransmission from other residential or workingpremises. Sound insulation for occupants isalso important within the same residential andworking premises when rooms serve differentpurposes, or different working and resting peri-ods apply, or enhanced insulation require-ments are desirable, Supplement 2 to DIN41 09 contains recommendations for standardand enhanced sound insulation. Table 2.6.79provides an overview of the correspondingsuggestions for residential and office buildings.DIN 4109 stipulates values for the permissiblesound level in noise-sensitive rooms in order toprovide protection against noise from buildingservices and operations. In order to maintainthese values, requirements are laid down forthe airborne and imoact sound insulation ofcomponents between "particularly noisy"rooms and those sensitive to noise (see table2.6.80). The latter are understood to be l ivingrooms, bedrooms, hospital wards, classroomsand offices, "Particularly noisy" rooms are:

. Rooms with "pafticularly noisy" building plantor services if the maximum sound pressurelevel of the airborne sound in these rooms fre-quently exceeds 75 dB(A).

. Rooms housing containers for rubbish chutesand access corridors to such rooms from theoutside.

' Rooms for craft or commercial activities,including sales activit ies, if the maximumsound pressure level ofthe airborne sound inthese rooms frequently exceeds 75 dB(A).

. Restaurants. caf6s. snack bars and the l ike.

'between corridors and bedrooms4. Hospi ta ls, c l in icsWalls between' patients'rooms' corridors and patients'rooms. examination or consultation rooms' corridors and examination or consultation rooms. patients rooms and work or nursing roomsWalls betuveen' operating theatres or treatment rooms' corridors and operating theatres or treatment roomsWalls between' intensive care rooms' corridors and intensive care roomsDoors between' examination or consultation rooms. corridors and examination or consultation rooms' corridors and patients'rooms. operating theatres or treatment rooms

: golllqgrs and operating t atm,gn! r,og!lt!5, Schools and similar places of educationWalls between. classrooms or similar rooms' corridors and classrooms or similar roomsWalls between' stairs and classrooms or similar roomsWalls between

> 5 2

> 3 7

' "particularly noisy" rooms (e,9, sports halls, music rooms,work rooms) and classrooms or similar roomsDoors befureen' corridors and classrooms or similar rooms1) Extractfrom table 3 of DIN 41092) Extract from table 2 of supplement 2 to DIN 41093) The following applies to walls with doors: R'*(wall) = R*(doo| + 15 dB; wall widths < 300 mm are not consideredhere.

42

37

37

a c

52

55

32

188

Sound insulation

.Bowl ing a l leys' Kitchens for hotels etc., hospitals, clinics,restaurants; not included here are smallkitchens, preparation rooms and communalkitchens.

'Theatres'Sports hal ls. Music and work rooms.

2.6.78 The airborne sound insulation index R'- according to the mass law

3 4 5 6 I 10 20 30 4050 70 100 200 300 500700

Area-related mass m' (kglm2)

c a nc v v-:cco v v

E.gEA ^ A

=C

; 3 0cfo@a 2 0c - -

c

Concrete, masonry, gypsum,g lass and s imi la r bu i ld ingmaterials

Sher ST" ' r t

to mm thicki

nr)er, timbel 0en\'atrv3S

for sound insulation within residential or to DIN 4109Suggestions forstandard soundinsulationreqd R'*dB

enhanced soundinsulationreqd R'*dB

Residential buildinqWalls without doors between "noisy"and "quiet" rooms with different uses,e.g. between living room andchild's bedroom.

> 4 7

Office buildinqsWalls between rooms for normal office activitiesWalls between corridors and rooms for normal office activitiesWalls to rooms for intensive mentalactivities or for handling confidential matters,e.g. between director's office andanteroom

In many cases it is necessary to provide addi-tional structure-borne insulation to machines,apparatus and pipes opposite soffits and wallsof the building. No figures can be specifiedhere because it depends on the magnitude ofthe structure-borne sound generated by themachine or apparatus, which is very different ineach case. Suppldment 2 to DIN 4109 pro-vides general design advice. There is norequirement with respect to the airborne soundinsulation index for the sound insulation ofwalls built to conceal building services andplant if the area-related mass of the wall is atleast 220 kg/m2 - such walls comply with thepermissible sound level for noises generatedby water pipes (including waste water pipes).Walls with an area-related mass < 220 kg/m2must be verified by a suitability test to provethat they are adequate. Excessive noise trans-mission in such situations can be effectivelyreduced by attaching a non-rigid facing of min-eral fibre board and plasterboard on the sideof the noise-sensitive room, Modern systemsfor such walls, with a facing or cladding the fullheight of the room, provide very good soundinsulation.

Sound insulation against external noise

Various noise level ranges, classified accord-ing to the actual or expected "representativeexternal noise level", form the basis of the pro-visions for the required airborne sound insula-tion of external components to protect againstexternal noise. Different requirements havebeen laid down for the bedrooms in hosoitalsand clinics. occuoied rooms in residentialaccommodation, hotel bedrooms and class-rooms as well as offices (see table 2.6.81 ).As the enclosing external components usuallyconsisi of several different surfaces with differ-ent sound insulation properties, the require-ments apply to the resulting sound reductionindex R'*,,"" calculated from the individualsound reduction indexes of the different surfaces.The required sound reduction indices have tobe increased or decreased depending on theratio ofthe total external surface of a room tothe plan area of the room. For instance, for astandard ceil ing height of 2.5 m, the require-ments given in table 2.6.81 are already accept-able for a room depth of 3 m and reductions ofup to -3 dB may be exploited for greater roomdeoths.The requirements for the resulting sound reduc-tion index for rooms in residential buildinos

Walls betvveen corridors and rooms for intensive mentalactivities or for confidential mattersDoors in walls between rooms for normal officeactivities or in walls between corridors and such roomsDoors rn walls to rooms for intensive mental activities 37or for handling confidential matters or in walls betweencorridors and such rooms

2.6.80 Requirements for airborne sound insulation of walls and floors between "particularly noisy" +ooms and thoseto be insulated

Type of room Airborne sound insulationindex R'* reqddB

75- 80with "particularly noisy"

or servrcesRooms for craft or commercial activities,

sales activitiesKitchens for hotels etc.,hospitals, clinics, restaurants,snack bars etc.

57

Kitchens as abovebut also in ooeration after 10 o.m.

57

Restaurants etc. not occuoied after 1 0 p.rh,Restaurants etc. - max. sound levelLAF < 85 dB(A) - also occupied after 10 p.m

Restaurants etc. - max. sound level 85 dB(A) < LAF < 95 dB(A)e.q. with electroacousticNote: LAF = time-related sound level, which is measured with the frequency evaluation A and the time evaluationF (= fast) as a function of the time.

189

Building science

Noiselevelrange

2.6.81 Noise level ranges and sound reduction indexR'",r"" to be maintained

Critical R'*,ru. reqd for externalexternal componentnoise (in dB)level Bed- Occupied Officesl)dB(A) rooms rooms

r) There are no stipulations for the external components ofrooms in which, owing to the nature of the activities car-ried out in those rooms, external noise which enters suchrooms makes only a minor contribution to the internalnoise level.2) The reouirements in these cases are to be establishedaccording to the local circumstances.

2.6.82 Aiborne sound insulation index of party wallswithout plaster, after Gosele

R'_ tdBlwithout with

plaster240 mm vertically perforatedclay bricks250 mm in-situ concrete240 mm hollow blocks ofn ' rmi^a ^^n^rd f6

200 mm storey-height aeratedconcrele panets

2.6.83 Different sound insulation of vertically perforatedclay brick walls with approximately equal area-related mass but different oerforations. afterJ. Lang

Unit cross-section Web cross-section(schematic)

| <55 35 30l l 56 -60 35 30 30i l l 61 -65 40 35 30lv 66-70 45 40 35v 71 -75 50 45 40vl 76-80 , ) 50 45vll > 80 2) 2) 50

50 531 1 5 3

16 49

45 47

r o uXc)c.5c 6 0.9blo _ ^O C U

ocl

8 4 0

500 1000 2000 Hz

Frequency f

WffiNAA: m'= 435 kglm2, R*= 59 dB

(continuous webs from outside to inside)B: m' = 42okglm2, R*= 49 dB

(webs offset with respect to each other)

30

X r

with a standard ceil ing height of 2.5 m, roomdepths of at least 4.5 m, and 10-60% windowarea, are deemed to be fulf i l led when the indi-vidual sound reduction indices given in tablesin DIN 4109 - according to the proportion ofwindow area - are maintained for the wall andwtndow.The sound reduction indices of venti lationducts and roller blind boxes and the associat-ed reference area should be taken intoaccount when calculating the resulting soundreduction index. Facil it ies for temporary ventila-tion (e.9. opening l ights and flaps) are evaluat-ed in the closed condition. those for oermanentventilation (e.9. sound-attenuated ventilationopenings) in the operating condition.The representative external noise level is deter-mined for the various noise sources usingappropriate methods of measurement andevaluation. DIN 4.109 contains a traffic noisenomogram in which the average level can beread off depending on the volume of traffic andthe distance of the building from the centre ofthe road. Special analyses for traffic situationsin which the nomogram cannot be used as wellas for rail and waterborne traffic are coveredby DIN 18005 part 2.For air traffic, i.e. airports, the "Law governingprotection against aircraft noise" lays downnoise protection zones. The provisions of thislaw, or more rigorous national regulations,apply within these protected zones.The representative external noise level for com-mercial and industrial ooerations makes use ofthe daily immissions value given in the devel-opment plan for the respective area categoryaccording to Germany's Noise Abatement Act.

Single-leaf walls

The sound insulation of thick, single-leaf, homo-geneous walls depends in the first instance ontheir area-related mass. The relationshipbetween the airborne sound insulation indexR'* and the area-related mass is shown in fig.2.6.78.The orerequisite for the correlationbetween the airborne sound insulation and thearea-related mass of a single-leaf wall is aclosed microstructure and sealed construction.lf this requirement is not fulf i l led, then the wallmust be sealed on at least one side by a com-plete covering of f irmly adhering plaster or cor-responding coating to insulate against directsound transmission [62], Table 2.6.82 showsthe difference in the airborne sound insulationindices for walls with and without plaster. Thecurve in tig.2.6.78 does not apply to l ightweightcomponents < 85 kg/m2 and, according to DIN4109, with an area-related mass > 630 kg/mscan only be used to describe the behaviour oftwin-leaf walls with continuous separating jointbecause in this range the achievable soundinsulation is l imited by the flanking compo-nents. The given sound reduction indices areachieved only if the average area-related mass

of the flanking components can be assumed tobe approx. 300 kg/m3.Besides the fact that sound insulation generallydepends on mass, the internal attenuation(material attenuation) of the material used isalso important to a certain extent. This attenua-tion is understood to be the ability of the mate-rial to convert part of the vibration energy intoheat and hence remove some ofthe energyfrom the vibration. lnvestigations carried out bythe Fraunhofer Institute for Building Physicshave shown that the airborne sound insulationindex can be set 2 dB higher thanks to thismaterial attenuation effect for plastered walls ofautoclaved aerated concrete and lightweightconcrete containing aggregates of pumice orexpanded clay with gross densities < 800 kg/m3and an area-related mass < 250 kg/mz.Acoustic studies at Braunschweig Universityhave established this 2 dB bonus for plasteredwalls of calcium sil icate with gross densities< B0O kg/m3 as well.J. Lang 11071 showed long ago that clay brickwalls with comoarable masses but differentoerforations exhibited differences in their air-borne sound insulation index of up to 10 dB(see fig. 2.6.83). Gosele discovered one expla-nation for this in the effect of thickness reso-nances [62]. The measured deviations wereattributed to the arrangement of the webs with-in the masonry units. In one case the webspass through the unit in a straight l ine andserve to stiffen the unit; in another they are off-set with respect to each other and work like aset of springs in series. More recent studieshave revealed that the sound insulation of wallsmade from perforated units depends not onlyon the arrangement of perforations in the unitsbut also on numerous other factors, such asthe type of mortar bed, thickness of plaster andformat of the unit [176]. Figure 2.6.84 showsthe difference between the measured and cal-culated sound reduction indices for walls ofperforated units with different area-relatedmasses and different proportions of perfora'tions. The effects of the various influencingvariables on the sound insulation are sum-marised in table 2.6.85,Positive effects are brought about by:. harder mortar. thicker coats of plaster. shorter masonry units. coarsely structured perforations with thickwebs,

The problems associated with perforatedmasonry units appeared in clay, calcium sil i-cate and concrete units, and - according tocurrent findings - are not restricted to a certainbuilding material.f able 2.6.87 orovides an overview of the char-acteristic airborne sound insulation indices formasonry with normal-weight and lightweightmortar and plastered both sides. These valuesmust be reduced by '100 kg/m3 for a gross

190

100

Sound insulation

2.6.84 Difference between measured and calculated(to DIN 4109 supplement 1) airborne soundinsulation indices in relation to proportion of per-forations for various walls of oerforated masonrvunits, after Scholl

2,6.85 Influence of masonry unit geometry and type olconstruction on the sound insulation of walls ofoerforated units. after Scholl

Inf luencing var iable AR.u"c 0 "I;

c c 0ooCoo - r=o

Arran gement of perforationsType of mortarThickness of bed jointsThickness of plasterUnit format

10-15 dBapprox. 5 dBapprox. 5 dB

5-10 dB5 d B

The figures given here represent the maximum change insound insulation ARmax that occurred upon changing therespective influences for a constant wall mass in themeasurement data available.

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0Proportion of perforations (7o)

2.6.86 Airbornesoundinsulat ionindexR'wofs ingle- leafr ig idwal lswi thanon+igidcladding; character is t icvaluesaccordins to QIN:||Sgjlpplpmg[ 1

Area-relatedmass ofsol id wal lkct/m2

Airborne sound insulation index R'wr)withoutc laddingdB

with claddinggroup AdB

with claddinggroup BdB

100200300400500

3745475255

4950545658

4849535557

density > 1OO0 kg/mo and 50 kg/m3 for a grossdensity < 1000 kg/m3 for walls of l ightweight orautoclaved aerated concrete oanels. as well asfor gauged brickwork using thin-bed mortar.Another possibil i ty of improving the soundinsulation of internal walls - also subsequently- is to combine the solid wall skin with a non-rigid cladding on the "noisy" side of the separ-ating wall, We distinguish between two groupsdepending on the connection to the rigid wall(see fig, 2.6.88). Claddings of group A arefixed to the heavy wall via a supporting frame-work, while those of group B are free-standingor bonded to the substrate via a resil ient con-nection using mineral f ibre boards. Table2.6.86 specifies airborne sound insulationindices for solid walls with a cladding on oneside. lf, for example, for thermal insulation rea-sons, insulating batts with a high dynamic stiff-ness are attached to a single-leaf rigid walleither fully bonded over the whole surface orjust at discrete points, this can degrade thesound insulation if the insulatinq batts arecovered by plaster.

Twin-leaf party walls

Party walls of two heavy, rigid leaves with a

continuous separating joint bring about a con-siderable reduction in the sound transmissionbetween, for example, adjoining apartments,The sound reduction index of a twin-leaf partywall with continuous joint is determined fromthe area-related mass of both leaves, includingcoats of plaster, similarly to single-leaf compo-nents, The direct sound transmission (withoutflanking transmission) of a twin-leaf wall of solidleaves is 12 dB higher than could be expectedfor a single-leaf solid wall with the same mass.The joint extends without interruption from topof foundation to roof covering (see fig. 2.6.90).A joint passing through the foundation leads tobetter sound insulation in the basement but asthis is a problem in terms of sealing the build-ing, this arrangement remains an exception.The 12 dB bonus may only be taken intoaccount when the followinq conditions arecomplied with:

'The area-related mass of each leaf must beat least 150 kg/m2 and the distance betweenthe leaves at least 30 mm.

. With a separating joint > 50 mm, the area-related mass of each leaf may be reduced to100 kg/m'z,

'The joint must be fi l led completely with tightlyjointed resil ient boards, e,g. mineral f ibreimpact sound insulation boards.

. Such fibre boards are not reouired when thearea-related mass of each leaf is > 200 kg/m'?.

The joint between the leaves should not bemade too thin as this can very quickly lead toacoustic bridges. On the other hand, the opti-mum leaf spacings in terms of sound insulationare higher than the minimum values given in

densi ty th ickness insulat ionindexr)21class mm R'w (dB)

Normalmortar

1) Applies to flanking components with an average area-relaled mass m'L.mean of 300 kglm'?1 dB for a "riqid" connection between claddinq and wall.

The values are reduced by

2.6.87 Airborne sound insulation index R'* of walls plastered both sides in relation to the bulk density class and wallthickness

Gross Wall Airborne sound Grossdensityclass

Wallthicknessmm

Airborne soundinsulation indexr)2)R'w (dB)Normal Lightvveightmortar mortar

Lightweightmortar

1 . 00.5

1 , 20 .6

L O

175240300365

40434547

175240300365

394244^ x 5 5 3

4548c l

47 3)

5052

175240300365

41444648

40

4C

175240300365

0.7 ----i7s

4345

42

49

175240300365

4852

56

240300365

03 175240300365

175 50240 53300 55365 57

444649c l

43464850

o.g r 7s240300365

44474951

175240300365

c t

545759

45485052

'?) A total of 40 kg/m2 has been taken into account for the coats of plaster.3) These gross densities are not generally cqlbrned with lightweig

191

Building science

2.6.88 Sound performance of favourable claddinos to DIN 4109 supplement 1Groupl) Wall construction DescriptionB - i , t h i c k n e s s > 2 5 m m .o v r d u u i l ' v r v i l r v v e r v r I

(no connection ,/,/,/./,/,/,/,/,/,/,/,/ ).'i plastered, gap between wall and timber studding > 20 mm,or resillent free-standing in front of heavy wall, construction to DIN 1 102Connectlon ffiW _ Ito wal l ) * 6

nl

o Cladding of p lasterboard to DIN 18180, th ickness l2.5 or 15 mm,N construction to DIN 1 81 8.1 (currently in draft form), or of chipboard to D lN 68763,'+

thickness 10-16 mm, gap between wall and timber studding > 20 mm, free-standing'?)

^ in front of heavy wall, with cavity filled3) between timber studding,o

>5oo x- Cladding of wood-wool lighhveight boards to DIN 1101, thickness > 50 mm,

,--;- I ? plastered free-standing with 30-50 mm gap in front of heavy wall, construction to

/. nt o DIN 1 102, a 20 mm gap is sufficient when filling the cavity according to footnote 3

A'TIV\NVV\N\7\7Oonl

Cladding of p lasterboard to DIN 18180, th ickness 12.5 or 15 mm,Ov and fibre insulation boardsa), construction to DIN 18181\ (currently in draft form), discrete or linear fixing to heavy wall.

T

(with connectionto wall)

O(o^1 1

(o

"l.rt

Cladding of wood-wool lighhr/eight boards to DIN 1 101 , thickness > 25 mm,plastered, timber studding fixed to heavy wall,construct ion to DIN 1102.

Cladding of p lasterboard to DIN 18180, th ickness 12.5 or 15 mm,construction to DIN 18181 (currently in draft form),or of chipboard to DIN 68763, thickness 10-16 mm, with cavity fill ing3),timber studding fixed to heavy wall2).

> 500-

> 500

adding claddings of group B, and by at least 10 dB for claddings of group A.2) In these examples the timber studding may be replaced by sheet steel C wall sections to DIN 18182 pt 1 .3t Fibre insulation materials to DIN 18165 pt 1 , nominal thickness between 20 and 60 mm, Iinear f low resistance E > 5 kNs/ma.4) Fibre insulation materials to DIN 18165 Dt L aDolication tvoe WV-s. nominal thickness > 40 mm. s'>5 l\,4N/m3.

2,6,89 Examples of twin-leaf walls - two leaves employing normal-weight mortar with continuous separating joint between buildings - in relation to gross density classesto DIN 4109 suoDlement 1

Airborne soundinsulation index

(dB)

Gross density class of unit and min. wallFacing brickworkboth sides

l\.4in. thickness oi Unrt grossleaves without plaster densitymm class

thickness of leaves for twin-leaf masonry10 mm plaster P lVboth sides (lime-gypsumor gypsum plaster)2 x 10 kg/m'

Min. thickness ofleaves without plastermm

15 mm plaster P l , P l lor P lll both sidesoder P l l l ( l ime, l ime-cement or cement plaster)( 2x25kg /m2)Min. thickness ofleaves without plastermm

Unit grossdensityclass

Unit grossdensityclass

57 0.60.911 . 4

0.6r)0,82)1 ,03 )1 / 5 \

0.66)0 ,87)1 .07)1 A

1.0u)1 . 21 . 41 . 8

62 0.60.90.91 . 4

67 11 . 21 . 41 . 8

2 x2402 x 1 7 52 x 1 5 02 x 1 1 52 x 2 4 O175 + 24O2 x 1 7 52 x 1 1 52x240175 + 2402 x 1 7 51 1 5 + 1 7 5

2x2402 x 1 7 52 x 1 5 02 x 1 1 52 x 2 4 O2 x 1 7 52 x 1502 x 1 1 52 x24O175 + 2402 x 1 7 51 1 5 + 1 7 5

o.72t0.94)1 .24)

0,56)0.87)0 ,97)1 , 20.9e)1 . 21 . 4t . o

2 x 1 7 52 x 1502 x 1 1 5

2x2402 x 1 7 52 x 1502 x 1 1 52 x24O175 + 2402 + 1 7 51 1 5 + 1 7 52 x 1 1 52 . 2 2 x 1 1 5 2 . 2 2 x 1 1 5 2

l OO kg/m'?'?) The gross density class may be 0.3 less when spacing between leaves is > 50 mm and weight of each individual leaf is > 100 kg/m',3) The gross density class may be 0.4 less when spacing between leaves is > 50 mm and weight of each individual leaf is > 100 kg/m'?.at The gross density class may be 0.5 less when spacing beween leaves is > 50 mm and weight of each individual leaf is > 100 kg/m'?,s) The gross density class may be 0.6 less when spacing between leaves is > 50 mm and weight of each individual leaf is > 100 kg/m'?.6) For leaves of gas concrete units or panels to DIN 4165 or 4166, as well as lightweight concrete units with expanded clay aggregate to DIN 18151 or 18152, the gross density

class may be 0.1 less when spacing betu/een leaves is > 50 mm and weight of each individual leaf is > 100 kg/m'?.7 ) Fo r l eaveso f gasconc re teun i t so rpane l s toD lN4 l65o r4 l66 ,aswe l l as l i gh twe igh t conc re teun i t sw i t hexpandedc layagg rega te toD lN lS l5 l o r lS l 32 , t heg rossdens i t y

class may be 0.2 less when spacing between leaves is > 50 mm and weight of each individual leaf is > 100 kg/m'?.e) The gross density class may be 0,2 less for leaves of gas concrete units or panels to DIN 4165 or 4166, as well as lightweight concrete units with expanded clay aggregate to

D IN 18151 o r . 18152 .

192

Sound insulation

the standard, A twin-leaf solid party wall com-plies with the minimum requirements of DIN4.109 (R'* = 57 dB) when the leaves are each115 mm thick. the unit gross density class is1.4 and a total of 20 kg/m2 of plaster has beenaoplied. To meet the recommendations ofenhanced sound insulation with at least 67 dB,the thickness of each leaf must be increased to175 mm for the same unit gross density class.Table 2.6.89 specifies airborne sound insula-tion indices for various wall constructionsaccording to DIN 4109 supplement 1: thesehave been calculated on the basis of the massdependency of R'* and the 12 dB addition.

Flanking components

The airborne sound insulation between roomsdependson the construction not only of theseparating wall but also of the flanking com-ponents and the connection between separat-ing wall and flanking components. The soundreduction indices for separating componentsgiven in supplement 1 to DIN 4109 apply toflanking components provided the followingconditions are fulf i l led:. The average area-related mass R'r.r""nof the rigid flanking components is approx.300 kg/m'?.

.A rigid connection to the flanking compo-nents is guaranteed when the area-relatedmass ofthe separating components exceeds150 kg/m'z.

. The flanking components are continuous fromone room to the next.

.The joints between separating and flankingcomponents are sealed.

lf the average area-related mass of the flankingcomponents deviates from approx. 300 kg/m2,the soecified sound reduction index of theseparating component must be corrected (seetable 2,6,94). The influence of the correctionvalue Kr,, is relatively small. In contrast, theconnection between the separating wall andthe solid flanking components has a consider-able in f luence (see f ig . 2.6.91) . This is the casewhen a l ightweight thermal insulation externalwall passes a heavy separating wall betweenapartments without being firmly connected toit. Measurements carried out by the FraunhoferInstitute for Building Physics revealed adegrading of the sound reduction index of upto 10 dB in the case of non-bonded, i.e. butt-jointed, walls whose joint subsequentlycracked and was sealed with a permanentlyelastic compound.A fixed connection between the flanking, solidcomponents and the separating wall or f loor,provided this is of a heavy construction, isdesirable. The example in fig. 2.6.91 showstwo types of junction between a separating wallbetween apartments and an external wall: withslot and with butt joint. The buti joint betvreenmasonry walls is equivalent to toothing and

slots in terms of building acoustics and rigidityof the connection in the sense of DIN 4109,provided the butt joint between the walls is fullyfi l led with mortar. This applies to masonry inwhich all joints are fi l led with mortar as well asto masonry without mortar to the perpends. Theinclusion of stainless steel anchors providesadditional security,Another typical case of increased flankingsound transmission occurs when an externalwall is provided with a rigid-clad (plaster orplasterboard) layer of insulation of rigidexpanded foam or wood-wool lightweightboards on the inside in order to improve ther-mal insulation (see fig. 2,6.93) [5]. The increasein flanking transmission brought about by theresonance effect is on average about 10 dB.This means that the requirements for separat-ing walls and floors befuveen apartments areno longer fulf i l led.

External walls

Facades are generally made up of walls withwindows and doors. The resulting airbornesound insulation index may be calculatedaccording to DIN 41 09 taking into account thetotal area and the areas of the individual com-ponents and their airborne sound insulationindices or - more simply - designed as shownin the example in figure 2.6.95 using tables ofvalues. The airborne sound insulation indicesof the windows are obtained from the testcertificates of manufacturers. Recommendedvalues for common types of windows with in-sulat ing g laz ing are inc luded in supplement 1to DIN 4109.The airborne sound insulation index of anexternal masonry wall depends on its construc-tion (see fig,2.6.92). For single-leaf externalwalls it is init ially the thermal insulation thatgoverns which wall material of low gross densi-ty is required. Wall thicknesses of 300-365 mmand gross densities of 500-BO0 kg/m3 generallyorovide sound reduction indices of between 45and 51 dB depending on the mass of the exter-nal component. lf a rendered thermal insulationlayer is attached to the outside, then - as hasbeen known for some time - coats of plaster onwood-wool l ightweight boards degrade thethermal insulation of a wall [61 ]. Later studieshave conflrmed this trend for insulation materi-als of high dynamic stiffness (polystyrene parti-cle foam), while insulation materials with lowstiffness (mineral wool) bring about improve-ments in some cases but a worsening in othersdepending on the weight of plaster and thematerial of the solid wall 11661. Investigationshave recently beencarried out on I4 different thermal insulationcomposite sybtems on a wall of calcium sil icateperforated units [147]. lmprovements in theinsulation sound index of up to 4 dB wereestablished for insulation materials with lowdynamic stiffness (mineral f ibre boards with

2.6,90 Joints between buildings with or without joint infoundation and ioint at roof level

Ground floor

Basement floor

2.6.91 Flanking transmission via flanking component;junction between party wall and external wallusing slot or butt joint

LOng-rermrel iabi l i ty

Tension-resistantconnectton

Flat anchor300 x 22 x 0.75 mm

V4A steel

Tension-resistantconnection

Flat anchor300 x 22 x 0.75 mm

V4A steel

-T

2 3 6 5 1

2 365 .1

f f i [

Building science

2,6,92 Examples of airborne sound insulation index R'*for various external wall constructions

Single-leaf external wall Single-leaf wall with thermal45-51 dB insulation composite system

47_51 dB

tl

I300 - 365

I - - f

Single-leaf wall withventilated curtain wall57 dB

r ig id expandedfoam boards.

175t-_|

Twin-leaf masonry with andwithout thermal insulation55-66 dB

horizontal f ibres or elasticized rigid expandedpolystyrene boards) and rendering with a higharea-related mass. Non-elasticized rigidexpanded polystyrene boards resulted in aworsening of -1 to -3 dB, mineral wool with ver-tical f ibres (laminated boards) -5 dB. lnstalla-tion by way of profiled rails presents thechance to achieve an improvement of 2 dB,even with a thin coat of plaster. Basically, anexternal wall with thermal insulation compositesystem can achieve a high degree of soundinsulation against external noise because theloadbearing wall does not need to contribute tothe thermal insulation and can therefore bebuilt using a heavy type of construction. Theairborne sound insulation index of a 175 mmthick calcium sil icate external wall with thermalinsulation composite system lies between 47and 51 dB depending on the particular con-struction.According to DIN 4109 supplement 1 , the posi-tive effect of a ventilated facade may not betaken into account when assessing the soundinsulation against external noise. Only the area-related mass of the inner leaf is assumed tocontribute to the sound insulation. However,solid external walls can achieve considerablyhigher airborne sound insulation indices withthe ventilated facades currently available[167]. Depending on the type of joints, type ofinsulation material and supporting construc-tion, the sound insulation of solid external wallswith ventilated facades may be increased byup to ARw = 15 dB with a careful considerationof all boundary conditions relevant to buildingacoustics. For a twin-leaf external wall, the air-borne sound insulation index is calculated fromthe sum of the area-related masses of bothleaves. The following amounts may be addedto the value determined in this wav for the twin-leaf type of construction:

. 5 dB if the area-related mass of adjoininginternal walls does not exceed 5O7o of theinner leaf of the external wall.

. B dB if the area-related mass of adjoininginternal walls exceeds 50% of the inner leaf ofthe external wall.

175t

2.6.93 Example of external wall cladding detrimental to sound performance (rigid thermal insulation boards on innerface), after Gosele

Externai wall 240 mmwithoutc ladd ing

withc ladd jngR',* = 47 dB

masonry, clad internallywith 12.5 mm -\plasterboard on 30 mm

r l

LJ

t t

f':]----JI J-tI L------lPf-_-_l

".]---_--]

63(dC

o

U

c. dB

o!.gc ^ ^o tiuFo=co

loa

2.6.94 Correction values KL,1 to DIN 4109 for the airborne sound insulation index R'*.* for rigid walls at flankingcomponents of average area-related mass m'r,."un

Type of separating component K, , in dB for average area-related mass

m'r,,"un in kg/m2

400 350 150Single- leaf , r ig id wal lsand floors

-1 -1

Single- leaf , r ig id wal ls +2 +1 0with non-r ig id c laddings

194

Sound insulation

It is possible to achieve an airborne soundinsulation index of 55-66 dB for cavity, partial-f i l l or full{ i l l external walls using the customaryforms of construction. The results of investiga-tions into calcium sil icate walls show, for thesame wall construction, the effects of theremaining air space and the type of insulationmaterial [92]. Using rigid expanded poly-styrene boards as the thermal insulation withan air space of 40 mm (padialJil l) produces aresult 2 dB higher than full cavity insulation.On the other hand, f i l l ing the cavity completelywith mineral f ibre boards or hyperlite loose{il lmaterial results in a 2 dB advantage over rigidexoanded olastic boards.

50 dB

2.6,95 Resulting sound reduction index R'*,.*.,"" (dB) in relation to sound reduction index of wall, sound reduction

index of window and its proportion of the area (%)

Wall: 50 dBWindow: 35 dBat 25% window area proportionFacade: 40 dB

Sound reductionindex of wall

SoLrnd reCuction index of window R.^, "

in dB for a window area proportion (%)O E I D

30dB 32 dB J 5 0 b

4Oo/o353535

25% 3Oo/o35 3435 3535 35

455055

40%333333

50o/o323333

25%373737

3Oo/o3637

5Oo/o343434

25% 30%393940

50o/o373737

3940

383838

andard constructionsSound red. Sound reduction index ofwindowindex 37 dB 40 dB

for a window area propoftion42 dB 45 dB

of wall 254/o 3Oo/o 25% 3ook 4Oo/o 5O/o 25o/o 4OVo 5O/o 257;o 3Oo/o SOa/o

50 a2 a2 a1 ag 45 44 43 43 46 46 45 44 48 48 47

60 43 42 41 40 46 45 44 43 48 47 46 45 51 50 49 48

65 43 42 41 40 46 45 44 43 48 47 46 45 51 50 49 48

b) External walls and windows with high sound insulation

Building science

2.6.96_ Bui ld ing mater ia ls c lasses to DIN 4102 part 1Buildrng materials class Buildilg authority deslsnglgnA incombustible materialsA 1A 2

combustible materialsnot readily flammable materialsflammable materialshighly f lammable mater ia ls-

2.6.97 Fire resistance.classes F to DIN 4102Duration of fireresistance in minutes

BB 1B 2B 3

Fire resistanceciassffi

F J U

F 6 0F 9 0F 120F 180

Fire protection

The chief tasks of fire protection are to preventfires from starting and spreading, and shouldthat happen, to guarantee opportunities torescue persons, animals and property as wellas create the right conditions for effective fire-fighting. The compulsory building authorityrequirements may be supplemented by therequirements of the insurers. Satisfying theseis not compulsory but does lead to markedreductions in insurance premiums.Besides active flre-fighting measures, e.g.sprinkler systems and fire alarms, the empha-sis is on maintaining preventive fire protectionthrough constructional measures (referred toas structural f ire protectiorl). This includesguaranteeing adequate fire resistance for thecomponents, using materials that do not gener-ate any, or at least no excessive amounts of,smoke or toxic gases during a fire, and reduc-ing the risk of f ire through careful planningmeasures. The latter includes the arrangementof f ire compartments; the safeguarding ofescape and rescue routes; and means forventing smoke and heat.In Germany the building authority requirementsregarding fire protection are defined in theFederal State Building Codes supplementedby statutes, bye-laws and directives. The stan-dard covering fire protection is DIN 4102 (18paris), which contains both testing standardsfor investigating and assessing fire behaviourand information on analysing fire protection forclassified building materials and components.

Building material classes

The behaviour of building materials in fire isassessed and classified according to DIN4102 part1 . Building materials are classifiedaccording to their combustibil i ty as class A(incombustible) or class B (combustible) (seetable 2.6.96), The assessment criterion forincombustible building materials of class A1 istheir behaviour upon the outbreak of a fire. lfbuilding materials of class A 2 include com-bustible components, the spread of f lame, thedensity of conflagration gases and their toxicitymust be evaluated. This is intended to ensurethat despite containing combustible compo-nents the overall behaviour can be comparedto the purely inorganic A 1 materials, Com-bustible building materials are assessed withregard to their f lammability and rate of spreadof flame, Building materials of class B 3 - high-ly f lammable - can make a direct contributionto the outbreak of fire and so the Federal Out-l ine Building Code prohibits their use. The testfor B 2 involves a small, defined flame, the testfor B 1 typically an object on fire within theroom (e.9. waste paper basket in one corner).The behaviour of the building material in f ire isimportant for the building authority require-ments for two reasons. First, the material must

> 3 0> 6 0> 9 0> 120> 180

Extensive fireln one room

No contribution to fireVerV limited fire

Single object Limited contribution to firea!!9p!4!le !e!lr&!119Acceptable behaviour in fire

on fireNo spread of flameto adjoining surfacesof a prod,uct

No performance established

2.6.99 Determination of fire resistance class, after Kordina/lvlever Ottens

2.6.98 Comparison of qerman building materials classes with future European classesFire situation Product pedormance European building DIN 4 j02 building

Material behaviourH igh-temperatureor combustion behaviourof material,e.g. of concrete,steel, masonry, timber

Duration of fire resistance

Fire resistance class+

Class of material used

uesrgnaton

196

Fire protection

meet requirements when it is used as the sur-face of a component (e.9, wall and soffitcladding); second, when used as part of theconstruction of a component. The essentialparts of fire-resistant components must consistof incombustible materials,The European classes for the fire behaviour ofbuilding products have now been accepted bythe Standing Committee for the ConstructionIndustry. They wil l be published after work onthe standard and the associated test methodshas been completed. A comparison betweenthe European and German building materialsclasses could well look somethinq l ike table2.6.98.

Fire resistance classes

The safety of a structure during a fire dependsnot only on the combustibil i ty of the materialsbut also - in particular - on the duration of f ireresistance of the components. The fire resis-tance class of a comoonent is defined as theminimum duration in minutes for which thecomponent wlthstands a specified fire test. In afire test the sample is subjected to a preciselydefined temperature gradient, the international-ly standardized standard temperature curve(see fig. 2.6.100), and is assessed accordingto the following chief test criteria:' Maintaining the load-carrying capacity (stabil-

ity) - under load for loadbearing componentsor self-weight for non-loadbearing compo-nents.

' Maintaining a maximum permissible rate ofdeflection in the case of components onstatically determinate supports.

. Maintaining the room enclosure (integrity andinsulation) in the case of walls so that noignitable gases can escape and no crackscan form which might lead to ignition. Theincrease in temperature on the side remotefrom the fire should not exceed 140"C onaverage and 180'C at individual measuringpornts.

As can be seen in fig. 2.6.99, the duration offire resistance is essentially determined by thebehaviour of the material and influences spe-cif ic to the component. In the case of masonry,failure takes place due to the reduction in cross-section resulting from temperature-relatedfatigue of the masonry units and dehydration ofthe mortar. The duration of fire resistanceenables a component to be assigned to a fireresistance class (see lable 2.6.97). Componentclassifications can be coupled to materialrequirements with respect to building materialsc lasses according to f ig , 2.6.101 in indiv idualcases.The fire resistance classes are designated withdifferent letters depending on the type of com-ponent (see table 2.6.102) .

of the materials used for

essential partsr) other parts not classedof components as essential partsr)

of components

2,6.100 Standard temperaturecurve

600

60 90 120 1s0 180

Duration of fire ln minutes

2.6.101 Designation of fire resistance classes in conjunction with materials used according to DIN 4102 paft 2

Fire resistance Building materials class to DIN 4102 pt 1 Designationz) Code

- 12009-o@6o

.gof

6oo- Rnn-o

F

ctass 10table2.2.3-2

F 3 0 BB

BCompongnts oIFire resistance class F 30Fire resistance class F 30 andwith essential parts madefrom incombustible materials')Fire resistance class F 30 andmade from incombustible materialsFire resistance class F 60Fire resistance class F 60 andwith essential pafts madefrom incombustible materialsr)Fire resistance class F 60 and

F 3O.BF 3O-AB

F 6 0

F 9 0

F 3O-A

--I OLI-D

F 60-48

F 60-Amade from incombusJible matelialsFire resistance class F 90Fire resistance class F 90 andwith essential parts madefrom incombustible materialsr)Fire resistance class F 90 andmade from incombustible materials

Fire resistance class F 120 andwith essential parts madefrom incombustible materialsr)Fire resistance class F 120 and

F 9O-BF 9O-AB

F 9O-A

F 120

F 180

-Fire resisunce class F 120 i :zuB

made from incombustibrle materials

F 120-AB

F 1 20-A

F 1 80-BF 180-AB

F 1 BO-A

a

ABB

Fire resistance class F 180Fire resistance class F 180 andwith essential pads madefrom incombustible materialsr)Fire resistance class F 180 andmade from incombustible materials

1) Essential parts include:a) All loadbearing pads and those contributing to stability; for non-loadbearing parts also the parts that contribute to

their stability (e.9. frames for non-loadbearing walls).b) In enclosing components a continuous layer in the component plane that may not be destroyed in the testaccording to this standard,In floors this layer must be at least 50 mm thick in total; voids within this layer are permissible.

When assessing the fire behaviour of materials, surface coatings or other surface treatments need not beconsidered,

2) This designation concerns only the fire resistance of the component; the building authority requirements formaterials used in fittino out the lnterior, and which are connected to the component, are not affected by this.

f jStandard

197

Building science

2.6.102 Codes for designating components when specifying the fire resistance classComponent Code for designating

fire resistance classWalls, floors, columns, beamsExternal wallsFire protection closures, e.g. fire doorsVentilation ducts, fire stops (fire protection closures)Glazing

F

TL+<G

2.6.103 Types of walls: examples of plan layouts for residential and industrial buildings, after Hahn

Types and functions of walls

ln terms of the function of a wall, for fire protec-tion purposes we distinguish between load-bearing and non-loadbearing, and betweenenclosing and non-enclosing walls. Figure2.6..103 il lustrates these terms using practicalexamples [68].A non-loadbearing wall is a platetype compo-nent that - also in the case of fire * is essential-ly loaded by its own weight and does not pro-vide buckling restraint to loadbearing walls.However, it must transfer wind loads acting onits surface to loadbearing components.A loadbearing wall is a plate-type componentmainly loaded in compression for carrying bothvertical and horizontal loads. Walls contributingto the stabil ity of the building or other loadbear-ing components are to be considered as load-bearing walls from the point of view of f ire pro-tection.An enclosing wall is a wall, for example, alongan escape route, adjacent to a staircase, or aparty wall or fire wall. Such walls serve to pre-vent fire spreading from one room to the nextand are therefore subjected to fire on only oneside. Enclosing walls may be loadbearing or -non-loadbearing.A non-enclosing wall is a wall subjected to fireon two, three or four sides during a fire.

Requirements

The fundamentals of building authority f ire pro-tection requirements are contained in therespective State Building Codes and the asso-ciated statutes, as well as in technical buildingprovisions and administrative rules. Figure2.6.104 explains the relationships and mutualinfluences. All State Building Codes, the corre-sponding implementation acts and administra-tive rules make a distinction between normalbuildings for normal purposes, e,g. housing,and those of special construction for specialpurposes, e,g. places of assembly, hospitals,industrial buildings.Normal buildings for normal purposes make adistinction between the different types of build-ings. The classification in building classesaccording to f ig . 2.6.105 depends on ladderaccess for the fire brigade and so is directlyrelated to the height of the building.Buildings of special construction or for specialpurposes are dealt with only in principle in thebuilding codes. The State Building Codes arecomplemented by special acts and directivesthat take into account the soecial circum-stances of high-rise buildings, places ofassembly, restaurants, hospitals, businesspremises, schools and industrial buildings.The relationship between the requirementspadly described in the State Building Codesand the abstract classification according tooart 2 and other oarts of DIN 4102 is carriedout on the basis of the definit ions contained insome State Building Codes, or according to

Apartment I

l - -

+< 1.0 i4)

T -

l > 1 . 0 ( ,

Apartment ll

Apartment l l l

, f < r . o @

Industr ia l buj ld ing

@ Loadbear ing, enclosing wal ls

@ Loadbearing, non-enclosing wars

@ Non- loadbear ing,enclosingwarrs

@ Short walls, formerly designated as piers

Fire compartments

+ Direct ionof f loorspan

2.6.1 04 Overview of building authority fire protection regulations

Resident ia l bui ld ing

Rl '+ lLttr

Buildings and structures of spe-cial types for special purposes

Places of assembly, garages,business premises, hospitals,h igh-r ise bui ld ings, schools,industr ia l bui ld ings

D tN 4102D tN 18081DtN 18230

198

Fire protection

the l ist of standard building material. The rela-tionshio between construction law and DIN 4102is given in table 2,6.106. The primary component of the fire safety concept in the buildingcode is the compartmentation principle: f ireshould be restricted to as small an area aspossible. The first "f ire compartment" is thefunctional unit, e.g. a whole apaftment in anapartment block, bounded by the floors, partywalls and staircase walls. At the very least, thefire should not spread to neighbouring build-ings, which can be achieved by relatively highrequirements being placed on the fire walls. Inaddition. the State Building Codes demandthat large buildings themselves be subdividedinto fire compartments. However, the compart-mentation principle can be fully effective onlywhen the openings necessary for the use ofbuilding are appropriately closed. This appliesto building service penetrations, e.g. electriccables, pipes, as well as to openings such asflaps, doors and gates.

2,6.105 Classi f icat ion of bui ld ings in f ive bui ld ing c lasses according to the bui ld ing codes

Bui ld ing c lass3

Low-r ise bui ld ingsL a d d e r a c c e s s H < 8 m

Free-standingresident ia l bui ld ing

t housing uni t < 2 housing units > 3 holsing units

Otherbui ld ingsH > 8 m

For FFL > 7m <22 m

Building authority

Fire-retardant

High-r isebui ld ings

At least 1 occupiedroom > 22 mabove FFL

Fire brigade access possiblewith scaling ladder for FFL < 7 m

F 30-

designation

Fire resistance class F 30Fire resistance class F 30 withessential parts made fromincombustible materialsFire resistance class F 30 andmade from incombustible materials

-AB Fire-retardant

F3o4 #tql4s

F 9O-AB Fire-resistantFire resistance class F 90 withessential parts made fromincombustible materials

FFL <22 m

2 ,6 .106 to DIN 4102 and construction law4 1

loadbearing parts madeA number of primary fire protection require-ments for components in residential buildingsare given in table 2.6.107. The example givenhere is taken from the State Building Code forNorth Rhine-Westphalia (there are sometimesslight differences between the codes of theindividual federal states in Germany); thisbuilding code was adopted in its entirety for allthe federal states of former East Germany.Free-standing residential buildings with onehousing uni t (bui ld ing c lass 1) are not inc ludedin the table because there are no requirementsfor the fire resistance classes of components insuch buildings. However, the basic require-ment, that no highly flammable building mater-ials may be employed, sti l l applies, Conse-quently, the thermal insulation materials usedin walls with external or internal thermal insula-tion layer and twin-leaf masonry with additionalthermal insulation between the masonry leavesmust comply with building materials class B 2or higher.

Fire walls

Fire walls according to DIN 4102 part 3 mustcomply with the following enhanced require-ments:.They must be built from materials of buildingmaterials class A to DIN 4102 part 1 .

.They must comply with the requirementsof f ire resistance class F 90 or higher toDIN 4102 part 2; loadbearing walls mustsatisfy this requirement under concentricand eccentric loading.

. Fire walls must remain stable and fulf i l theirenclosing function after being subjected to animpact load (3 x 200 kg of lead shot in sack).

However, it is not only adequate to ensure thatfire walls comply with test requirements - theymust be properly located in practice andproperly constructed.

Fire resistance class F 90 andmade from incombustible materials

F 9O-A Fire-resistant andmade from incombustible materials

2,6.107 Summary of the most important requirements for structural fire protection for components customary in

buildings using the North Rhine-Westphalia Building Code as an exampleClass of bui ld ing ,Type ofbui ld ing

Any bui ld ing Other bui ld ings

of low height (FFL < 7 m)< 2 housing uni ts , > 3 housing uni ts bui ld ings

Residential

Loadbearing walls RoofOtherBasement

01 )F 3O-BF 3O-AB

Or tF 3O-ABAF 9O-AB

apart fromfrom high+ise

0 r )F 9O-ABF s94E_

Non-loadbearino external wallsExternal wall

A or F 30-B0B 2 ->suitable

B1Cladd ingBui ld ing end wal ls F 9O-AB

(F 30-B) +

0 r tF 3O-B

BWF 9O-AB

0 r )F 30-AB3)

/tron_R\

Floors

Parly wails - -

RoofOtherBasemenl

0 r )F 9O-AB

F 3O-B F 9O.AB F 9O-ABFgO-AB BW BWF 9O-AB

4 0 m F 9O.ABParty walls betuueen Roof

OtherF 3O-B F 3O-B F 3O-B

F 9O-ABStaircase

sat, itgqt=

f lonorallv annocqihla Walls - F 30-B F 30-AB

corndors as F 3O-ABA

qpgg!9q9

routes CladdingWalls, floorsOpen walkways

adjacent external walls Cladding1) Inside of roof F 30-B for buildings with gable facing the street'z) F 30-B for buildings with < 2 storeys above ground level3t F 30-B for buildings with < 2 storeys above ground level

F 3O-B F 60-48RoofFloorWalls

000

0F 3O.ABF 9O.AB

0F 9O-ABBW

00

F 9O-ABA

F 30-B/A for buildings with > 3 s.toreys atlove ground level

199

Bullding science

2.6.108 Fire protection requirements in the vicinity of fire wallsComponent ReqLlirements

WAIIS

+ impact load 3 x 3000 NmF 9 0No restrictionT 90 doors (self-closing mechanism)F 90 fire protection glazingS 90 fire stop to cable penelrations

nrr"ng

Loadbearing and bracing componentsNo. of openingsClosures to openings

The respective Federal State Building Codemust be adhered to

Between buildings forming a terraceWithin large bui ld ings

Depending on height of building and roof covering:< 3 full storeys extending to underside of roof covering> 3 full storeys at least 300 mm above roofsoft roof covering at least 500 mm above roof

Components may intrude, provided the remaining cross-sectionof the wall remains sealed and stable to F 90 standard.

109 Fire for ventilated cRequired building materials class ton<2 fu l l s t o reys

4n > 2 f u l lstoreys, high-r ise bui ld ings

The fire protection requirements for fire wallsare summarized in 2.6.108. DIN 4102 oart 4contains details of permissible slendernessratios and minimum thicknesses of f ire wallsand their junctions with other components.

Complex party walls

Complex party walls are merely referred to in afootnote in DIN 4102 part 3 because this is aninsurance industry term, The main point to benoted is that the provisions of the insurers, withlimitations on openings, call for f ire resistanceclass F 180, Complex walls must pass throughall storeys without any offsets. Componentsmay not intrude into nor bypass these walls..

Classification of proven components

DIN 4102 part 4 contains details of buildingmaterials, components and special compo-nents whose fire behaviour has been classifiedon the basis of tests. The products included inthe standard have already been verified interms of their behaviour in fire. The fire protec-tion classification of the walls is carried outaccording to:

'wall material. wall thickness. type of fire (from just one side or from morethan one side)

' utilization of the load-carrying capacity ofthe wall

lf a component is not fully utilized, its load-car--rying capacity during a fire is greater thanwhen it is uti l ized 100%. Therefore, in the stan-dard we distinguish between the utilization fac-tors o, = 1 .0 (1 00% utilization), dz = 0.6 (60%utilization) and c[', = 0.2 (2Oo/o utilization). Theclassification of walls, shallow lintels and chan-nel blocks filled with concrete can be found intables 38-42 of DIN 4102 part 4. The informa-tion in the tables applies to masonry accordingto DIN 1053. Plaster on the side facing the fireprolongs the duration of fire resistance. Thevalues in brackets in the tables relating to wallthicknesses refer to olastered walls becausecertain plasters have a positive influence onthe fire behaviour of masonry walls. Twin-leafwalls only require plaster on the outer faces.The tables are valid for all types of perpendsaccording to DIN 1053 part 1 , i.e. for perpendsfully f i l led with mortar, for "t ipped and tailed"perpends, and perpends without mortar (inter-lock or tongue and groove). Perforations inmasonry units or wall panels may not run per-pendicular to the plane of the wall.Masonry readily satisfies the requirements offire protection, generally through the wall thick-ness required for structural or building sciencereasons. Therefore, the extensive tables in DIN4102 parl4 can be considerably reduced byspecifying fire resistance class F 90 and 100%

Cladding B 2Support ingconstruct ion B2Thermal insulationMeans of

B 2A q t

B 1B 2 1)2)

B 1A 4 )

A 3 )

' )There are no restr ic t ions on using B 2 bui ld ing trame-like suppofiing constructions, provided the gapbetween cladding and insuiation does not exceed 40 mm and window/door reveals are protected by class A build-ing materials.

'?) The Bavarian Building Code permits timber supporting constructions for buildings up to 30 m high.3) Does not apply to elements for retaining layers of insulation.a) Does not apply to anchor systems covered by a buildirig authoritv certificate,

2.6.110 Single-andtwin- leaf f i rewal ls toDlN4102part .4|able45,Permissib leslenderness,min.wal l th icknessand min, spacing of leaves (fire load on one side). Values in brackets apply to walls with plaster, Design toDIN 1053 parls .l and 2 with permissible slenderness ratio ho/d. The eccentricity e may not exceed cll3.

Type of wall Masonrywithout plaster with plasterMin, thickness d (mm)for single-lealconstruction

twin-leaf6)construction

Walls of masonry3r to DIN 1053 parts 1 and 2using normal-weight mortar of mortar group ll,l l a o r l l l , l l l a .Masonry units to DIN 105 part 1 of gross density class > 1 .4

> .1.0

DIN 105 pad 2 of gross density class > 0 ,8

240300(240)JOC' '

2 x 1 7 52 x 2 O O(2 x 175)2 x24O

x 1uni ts to DIN 106 part 1 ' ) and DIN 106

part 1 A1 " as well as part 2 of gross density class > 1 . 4> 0.9

240300(300)300

2 x 1755)2 x 1 7 52 x2OO(2 x 175)2x240

units to DIN 4165 of gross density class > 0 .6> 0.64)> 0.56)

300240300

x 1 72 x24O(2 x 175)2 x

Masonry units to DIN 1 1 81 52 and > 0.8 240(1 75)300

X 1of gross density class (2 x 175)

2 x24O> 0.6(2 x 175)

'r Also with thin-bed mortar.2) d = 175 mm when using thin-bed mofiar and gauged brickwork.3t Utilization factor d2 < 0.6 when using lightweight mortar.o) Applies to thin-bed mortar and gauged brickwork with mortar to perpends and bed joints.5)d = 150 mm when using thin-bed mortar and gauged brickwork.6)Applies to thin-bed mortar and gauged brickwork with tongue and groove only in the case of mortar to perpends and

hcd ininiq

200

(240\

Fire protection

degree of uti l ization. Tables 2.6.11 1-1 '1 3 spe-cify the minimum thicknesses required toachieve fire resistance class F 90 employingmasonry of standard units. Besides the fireresistance class, f ire walls must also complywith the conditions given in table 2.6,110 withregard to slenderness ratio and wall thickness.Claddings may not be used in order to reducethe soecified wall thicknesses. Thinner wallsthan those given in DIN 4102 part 4 have beenproved for f ire walls of clay, calcium sil icate,autoclaved aerated concrete and lightweightconcrete units in tests to DIN 4102 part 3 [7,76,134,2091. Reference [67] contains com-prehensive information on fire protection inmasonry structures with practical examples.

External walls with thermal insulation

Single-leaf external walls with an external, ren-dered thermal insulation layer (thermal insula-tion composite system) are assessed in fireprotection terms according to the type of insu-lation material used.

Thermal insulation composite systems withinsulation materials of not readily f lammablepolystyrene particle foam (building materialsclass B 1) and a maximum thickness of 100 mmcomplying with a general building authoritycertificate may be used on masonry up to thehigh-rise building l imit. Thermal insulationcomposite systems using mineral materials,e.g. mineral wool products of building mater-ials class A 1 or A 2. are considered as a coatof plaster when classifying the wall. In terms offire protection, the external wall is equivalentto a plastered wall without thermal insulation.Thermal insulation composite systems withinsulation materials of building materials classB 2 may be employed only on buildings with amaximum of two full storeys. The fire protectionrequirements for curtain wall venti lated facadesdepend on the height of the bui ld ing; therequirements with respect to building materialsclasses for facade components are summar-ized in table 2.6.109. The fire protectionrequirements sti l l apply for venti lated external

wall claddings upon which doubt has beencast by certain tests [22].Thermal insulation materials of building materi-als class B 2 may be used up to the high-risebuilding l imit for partial- or full-f i l l cavity walls.In contrast to this, buildings of medium height(7-22 m) require that continuous layers of F 30-AB and F 90-AB components must consist ofc lass A bui ld ing mater ia ls .Flammable insulation materials of buildingmaterials class B 2 are permitted in the case o1internal insulation for buildings up Io 22 mheight. Special regulations apply to escaperoules.

2.6.1 13 Non-loadbearing, enclosing walls of masonryor wall panels to DIN 4102 part 4 table 38.Values in brackets apply to walls plasteredboth sides

Construction features Min. thickness (mm)for fire resistanceclass F 90

mmWalls

2.6.111 Loadbearing, enclosing walls of masonry toDIN 4102 part 4 table 39. Values in bracketsapply to walls plastered both sides. Utilizationfactor cr, = 1.9

Construction features Min. th ickness (mm)for fire resistanceclass F 90

Walls

o .

Z 77-lo'- d 1 m

2.6.112 Min. th ickness d of loadbear ing, non-enclosingwalls of masonry to DIN 4102 part 4 table 40(fire load on more than one side). Values inbrackets apply to walls plastered both sides.Utilization factor u, = 1.6

Construction features Min. th ickness (mm)for fire resistanceclass F 90

d 1dd l

Autoclaved aerated concreteBlocks & gauged brickworkto DIN 4165Gross density class > 0.5

175

(1 50)

Autoclaved aerated concreteBlocks & gauged br ickworkto DIN 4165Gross density class > 0.5using r)2)I i ^hh^ ,d i^h+ ^^n^r6 t6

Hol low blocks to DIN 18151Sol id br icks & blocks to DIN 18152Concrete masonry units to DIN 18153Gross density class > 0.6

Autoclaved aerated concrete 1001)Blocks & gauged brickwork to DIN 4165 (75)Panels & gauged brickwork elementsto D IN 4166

240(1 75)

240(1 75)

1)2) Lightweight concreteHol lowwal l e lements to DIN 18148Hol low blocks to DIN 18151Sol id br icks & blocks to DIN 18152Wal l e lements to DIN 18162

95(70)Lightweight concrete

Hol low blocks to DIN 18151Sol id br icks & blocks to DIN 18152Concrete masonry units to DIN 18153

175(140)

to DIN 105 pt 1 1

Gross density class > 0.6r)3)

Clay bricksSolid & vertically perforatedto DIN 105 pt 1using rr (1 1 5)Clay bricksLightweight & veftically perforatedto DIN 105 pt 2Gross density class > 0.8

t ) 3 )

Clay bricksSolid & vertically perforated

Li ghtwei ght vertically perloratedto DIN 105 pt 2Gross density class > 0.8using 1)3)

Perforatjon types A & B (115)

Li ghtwei ght vertical ly perforatedbricks type WUtilization factor 02 = 1.0 (24o)eablnm-ililSolid, perforated, blocks, hollow blocks &gauged brickwork to DIN 106 pt 1 & 1 A1 140

(1 15 )DIN 106 pt 1 A1Facing bricks toD IN 106 p t 2

1t2)

1) Normal-weight mortar2) Thin-bed mortar3) Lightvveight mortara) The values apply only to masonry of solid bricks, blocks

and gauged brickwork when 3.0 < exjst o < 4,5 N/mm2.

Clay bricksSolid & vertically perforatedto DIN 105 pt 1Li ghtwei ght vertically perforatedto DIN 105 pt 2

u s i n q r ) 3 ) Concrete uni ts to DIN 18153

t / c

t t c

(100)

P a r f n r a t i n n t \ / n a a A R R

Li ghtweight vertical ly perforated

( 1 1 5 )

124o'\

High-strength bricks & engineeringbr icks to DIN 105 pt 3High-strength engineering bricksto D IN 105 p l 4Calc ium si l icaLe 1 15Solid, perforated, blocks, (100)hollow blocks & gauged brickworkt o D I N 1 0 6 p t l & 1 A lGauged br ickworkto DIN 106 pt 1 &DIN 106 pt 1 A1Facing br icks lo DIN 106 pt 2r) d > 50 mm when using thin-bed monars.

Calcium silicateSolid, perforated, blocks, hollowblocks & gauged brickwork toD IN 106 p t 1 & ' l A1Facing br icks to DIN 106 pt 2

1)2)4 \

1) Normal-weight mortar'zt Thin-bed mortar3t Lightweight mortara) The values apply only to masonry of solid bricks,

blocks and gauged brickwork when3 .0<ex rs to<4 ,5N /mm'? .

1 1 5(1 15 )

201

Variables

Units and symbols for building science

Symbol Designation Uni t

m2

Moisture correction factor

F^ Reduction Jactor for sunshading

Specific transmission heat loss wKHeat conduction wn<Heat, heat energy J o r W s

O Annual heating energy requiremenl kWh/a

Qn Annual heating requirement kWh/a

O" Heat gain kWh/a

Qr Heat loss kWh/a

o Primary energy requiremenl kWh/a

O Energy requirement from renewable sources kWh/a

Q1 Total heat losses due to heating system kWh/a

O* Energy requirement for hot water provision kWh/a

Thermal resistance m2KlW

I nternal,/External surface resistance m2KNl

Total thermal resistance (air-to-air resistance) m2KAA/

Solar heat penetration

U (formerly k in Germany) Thermal transmittance W/m2K

Thermal transmittance, window frame W/m2K

Thermal transmittance, glazing Wm'?K

u,^, Thermal transmittance, window W/m2K

Volume m3

Water vapour diffusion resistance m'?hPa4<g

Temperature diffusivity m2/s

Heat penetration coetf icienl J/m'?Kso 5

Specific heat capacity J,&gKThickness

Cost index related to primary energy requiremenl

Temperature factor

Solar total energy transmittance

Water vapour diffusion flow rate kg/m'h

Thermal surface resistance coeff icient W/m'?K

Mass kg

ffiwr Area-related condensation mass kg/m2

ffiwv Area-related evaooration mass kg/m2

Air change rate No,,tr

P' P" Water vapour partial pressure,

water vapour saturation pressure Pa

Pi , P" Water vapour partial pressure, internal/external Pa

Heat flow rate W/m2

Water vapour diffusion-equivalent air layer thickness

Time

Mass-related moisture content kg/kg

Water absorption coeff icient kglm2ho 5

'4 (eta) Degree of utilization

$ (theta) Temperature .C

Air temDerature. internal/external .C

.Cr1 . Internal surface temperature

L (lambda) Thermal conductivityp (mv) Water vapour diffusion resistance index

p (rho) Gross/bulk density kg/m3

O (phi) Heat flow

Relative humidity

I (chi) Discrete thermal transmittance WiK

v (psi) Linear thermal transmittance WmKVolume-related moisture content m3/m3

m

K

J

s

h

P

kg

d'cdB

Hz

mere

Watt

Kelv in

J O U I e

year

second

hour

Pascal

kilogram

day

degree Celsius

decibel

Heftz

Sound jntensity W/m2

Sound oressure level. sound level dB

Sound reduction index dB

dBR,n, Airborne sound insulation inde^

Frequency t1z

202

Sound pressure Pa