Accepted Manuscript

Title: Thermal insulating plaster as a solution for refurbishinghistoric building envelopes: first experimental results

Author: Lorenza Bianco Valentina Serra Stefano FantucciMarco Dutto Marco Massolino

PII: S0378-7788(14)00941-4DOI: http://dx.doi.org/doi:10.1016/j.enbuild.2014.11.016Reference: ENB 5479

To appear in: ENB

Received date: 15-10-2014Accepted date: 1-11-2014

Please cite this article as: L. Bianco, V. Serra, S. Fantucci, M. Dutto, M.Massolino, Thermal insulating plaster as a solution for refurbishing historicbuilding envelopes: first experimental results, Energy and Buildings (2014),http://dx.doi.org/10.1016/j.enbuild.2014.11.016

This is a PDF file of an unedited manuscript that has been accepted for publication.As a service to our customers we are providing this early version of the manuscript.The manuscript will undergo copyediting, typesetting, and review of the resulting proofbefore it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers thatapply to the journal pertain.

Page 1 of 24

Accep

ted

Man

uscr

ipt

Thermal insulating plaster as a solution for refurbishing historic building envelopes: first experimental

results

Lorenza Bianco1, Valentina Serra

1*, Stefano Fantucci

1, Marco Dutto

2, Marco Massolino

2

1 Department of Energy, Politecnico di Torino, TEBE Research Group, Turin, Italy

2 Vimark srl - Peveragno (Cuneo), Italy

Corresponding author* Valentina Serra, Politecnico di Torino, Dept. of Energy, Corso Duca degli Abruzzi 24,

10129 Torino, 0039110904431, valentina.serra@polito.it

ABSTRACT

In Italy, historic buildings constitute 20% of the built environment. Although historic buildings are usually

excluded from the obligation of adopting specific energy standard, energy related aspects should be

nevertheless faced and managed in order to exploit the building “usability” potential, to attain indoor

environmental quality and energy efficiency conditions. The energy refurbishment of this kind of building is,

however, a very complex matter that leads to a number of question concerning buildings conservation and

valorisation aspects. A non invasive technique, that is, the application of thermal plaster to the internal side of

a building envelope, has been investigated in this paper. Thanks to its relatively easy installation and

reversibility, thermal insulating plaster seems to represent a very interesting solution as it is able to offer a

good compromise between energy and conservation aspects.

The aim of this work is to present a thermal, vegetal based insulating plaster, which has recently been

developed within a research project, and to investigate its potential to reduce the heat flux exchanged through

the vertical envelope of historic buildings, by means of measurements carried out in both the laboratory and in

the field, for a real case application.

KEYWORDS thermal insulating plaster, building envelope, historic building, built heritage, energy

refurbishment, retrofitting.

1. INTRODUCTION

The refurbishment of existing buildings is a crucial point for the achievement of the energy and climate

objectives of the European Union (EU) for 2020 and 2050. The energy performance of existing buildings

is still very poor, and the construction sector is responsible, on average, for 35% of the energy

consumption in Europe and in Italy [1]. The problem is made, even more complex in Italy, by the

*Manuscript

Page 2 of 24

Accep

ted

Man

uscr

ipt

remarked presence of historic buildings, which constitute 20% of the existing building stock (2 out of 10

buildings were built before 1919) [2].

Passing from energy related aspects to the cultural ones, according to the Italian Constitution (art.9),

historic buildings should be preserved and protected because they constitute a source of knowledge of the

architectural history of the country. Consequently, the strategy concerning the protection of historic

buildings must be enhanced, and it could be more easily implemented if buildings continue to have a

function and a role, as theorized by Annoni in 1946 [3]. Specific maintenance interventions, are therefore

needed to refurbish the buildings from the energy point of view. Although historic buildings are usually

excluded from the obligation of adopting specific energy standards, energy related aspects should be faced

and managed in order to exploit the building “usability” potential, so as to create acceptable indoor

environmental quality and energy efficiency conditions.

The energy refurbishment of this kind of building is a very complex matter that leads to a number of

question concerning conservation and valorisation of the building aspects and which require “one case at a

time” approach [3], when deciding how and where to intervene on a building.

A literature review has shown, that a qualitative and quantitative approach to the energy and sustainability

of heritage buildings needs to be applied [4]. Furthermore, the lack of a methodology, technologies and

knowledge on historic building retrofitting has been observed. Till now, only a few experimental and

modelling activity researches have been conducted on this topic [5,6]. One study has recently presented a

methodology, based on MCDM analysis (multiple-criteria decision-making), to select the best solution for

the internal insulation of a brick wall in a historic building [5].

Thanks to the relatively easy installation and reversibility, thermal insulating plaster seems to represent a

very interesting solution, as it is able to offer a good compromise between energy and conservation

aspects for those buildings where it can be applied (i.e. no frescoed walls). The first results of a research

project, aimed at developing new kinds of plaster and insulation materials with low embodied energy, are

presented. In this work, the analysis has focused on a new thermal, vegetal based plaster, developed

specifically for internal insulation. In particular, the study here presented deals with its applicability to the

internal side of an existing historical building envelope under refurbishment, and assesses the impact on the

thermal flux reduction.

Page 3 of 24

Accep

ted

Man

uscr

ipt

The thermal insulating plaster has been tested in the laboratory to assess its thermal properties and in a

real historic building, to investigate its potential to reduce the heat flux exchanged through the vertical

envelope on which it has been applied.

2. THERMAL INSULATING PLASTER

Plaster has been used for thousands of years as constructive element in buildings, especially in Europe. The

versatility of this material allows it to be both used internally and externally, with the possibility of applying

rendering or plastering mortar to different substrates, constructions and compositions. Thermal insulating

plaster represents one of the possible solutions that can be adopted to face energy related problems in

existing and historic buildings. The workability of thermal plaster is very similar to that of traditional plaster,

as it can be used on non-aligned, out of square, or even on curved supports. Thermal insulating plaster is in

fact flexible and can be suitable for any architectural or design solution. Moreover, thermal insulating plaster

is characterised by a high water vapour diffusion coefficient, with a water vapour resistance factor (µ value)

of between 5 and 15. For this reason, the application of this technology to existing walls is possible for

envelopes affected by capillary rising damp, a problem which is very often present in historic buildings.

Thermal insulating plaster has been studied not only to be a finishing or a protection layer of the walls, but

also to improve their thermal resistance. These special kinds of plaster are characterised by thermal

conductivity values that are more than ten times lower than traditional plaster (standard lime plaster 0.7

W/(mK)) and they are divided into two categories: plaster with natural binders (natural hydraulic lime) and

plaster with cement or artificial binders. These types of plaster are usually pre-mixed and ready to use and

are made with Light Weight Aggregates (LWA), such as cork, clay, perlite, pearls of expanded polystyrene,

expanded glass, etc. LWA are able to significantly improve the thermal and acoustical insulation

performances of the component. Additionally, the weight of the component is noticeably reduced, compared

to traditional ones [7].

New kinds of thermal insulating plaster are still being studied to reduce their thickness and to improve their

thermal conductivity. Research is moving towards new aggregates, that is, innovative or natural materials.

High-tech solutions, such as aerogel or phase change material (PCM) based plaster, are also being

investigated.

Page 4 of 24

Accep

ted

Man

uscr

ipt

In this paper, the results related to traditional and advanced materials for thermal plaster are presented, with

particular focus on the thermal properties of a vegetal based plaster. Vegetal aggregate materials, derived

from corncobs, were added to a natural Wasselonne hydraulic lime and expanded silica (perlite), and the

resulting plaster was tested through a laboratory analysis and in field measurements. The particle size

distribution of the ingredients was studied in the laboratory to obtain the best combination from the physical,

mechanical and thermal points of view. Wasselonne lime is a Natural Hydraulic Lime (NHL 2, according to

the EN 459-1:2010 standard [8]) that has been extracted since 1932 in the Alsace region, France, and it

constitutes a significant percentage of the final product. The natural aggregate in these prototypes was 43%

(33% corncobs and 10% of dried expanded silica) and it played a double role: firstly, it contributed to an

improvement in the insulation of the plaster by exploiting a waste material (i.e. the corncobs) and, secondly,

the mechanical properties of the plaster were improved and the risk of cracking was hence reduced.

Furthermore, the natural binder gave a high water vapour diffusion coefficient to the plaster (that is, higher

than cement binders). Application tests were carried out by spraying the thermal insulating plaster onto a test

wall using a plastering machine (Figs. 1a and 1b).

The results have showed that this technology is capable of supporting greater thicknesses of thermal

insulating plaster (above 10 cm) than traditional insulating plaster. The same result could only be achieved

using a traditional plaster through the repeated application of thin plaster layers onto its support with the

consequent risk of cracking. The sample that passed the first mechanical test and presented the best

performance was named VGT_04, and the results related to this sample are hereafter presented. The results

concerning long - term decay and the marcescence and oxidation processes are not yet available, but these

important aspects are currently under investigation. Furthermore, on the basis of the ISO 14040:2006

standard [9], a life cycle analysis is also being conducted.

3. THE MEASUREMENTS

3.1 Laboratory measurement methodology

Laboratory measurements have been performed to assess the equivalent thermal conductivity of the thermal

plaster samples (10 cm thickness and 60x60 cm size, as shown in Figure 2a). A set of experimental

measurements was carried out with heat flow meter apparatus, in accordance with the EN 12667:2001

international standard [10]. The apparatus, a Lasercomp FOX600, consists of a single sample, heat flow

Page 5 of 24

Accep

ted

Man

uscr

ipt

meter with a guarded ring equipped with two plates containing heat flow meters placed above and below the

sample (Fig. 2b). Specifications details of the equipment are given in Table 1.

The instrument was designed and set up in accordance with the ASTMC518, 1991 [11] standard and it was

calibrated with “1450b NIST SRM” calibration reference samples and an EPS sample (expanded

polystyrene). All the samples were previously tested and certified by NIST. In order to avoid any additional

surface resistances, due to the sample discontinuity, all the specimens were sandwiched between two rubber

3 mm sheets with a thermal conductivity of 0.073 W/(mK) at 10 °C. The uncertainty of the measured thermal

conductivities were determined for each measurement in accordance with ENV 13005:1999 [12]. The

resulting uncertainty values were within ±2%, according to EN 12667:2001 [10] (annex B), including the

additional uncertainty caused by subtracting the resistance of the rubber sheets.

Laboratory measurements were performed on two different samples (A and B) of the same thermal plaster

(VGT_04 with natural Wasselonne hydraulic lime and vegetal aggregate materials). Before the tests, both

specimens were dried to constant mass in a ventilated oven for 48 h at 60°C to determine their mass. The

relative loss in mass was calculated comparing the mass of the samples before and after the drying cycle. The

tests were carried out at three different mean temperatures: 10, 25 and 40 °C, respectively, with a

temperature difference of 20 °C, to minimize temperature - difference measurement errors.

As is known the measurement principle is to create a constant temperature difference between the upper

plate and the lower plate, and to measure the specific heat flux and surface temperatures in steady state

conditions. The equivalent thermal conductivity [W/ (mK)] is then calculated using Equation 1, where s is

the sample thickness [m], q is the specific heat flux [W/m2] and ∆ts is the temperature difference between

the two faces of the plate [°C].

seq tqs /)( [W/m°C] (1)

3.2. Laboratory measurement results

The sample specifications are shown in Table 2. Samples A and B differ mainly as far as the density is

concerned: sample A presents a higher density than sample B for both humid and dried samples. The thermal

conductivity of the two different samples is reported in Table 3. In Figure 3, which shows the equivalent

thermal conductivity vs. average temperature of the plates, it is possible to observe the influence of the water

content on the thermal conductivity.

Page 6 of 24

Accep

ted

Man

uscr

ipt

Both samples demonstrate quasi-linear behaviour: the difference between the dry and the humid samples is

between 8% and 17% for sample A, and between 3% and 4% for sample B, depending on the set-point

temperatures. The divergence between samples A and B was due to their different water contents.

The experimental results show that vegetal aggregates have a great potential to reduce the thermal

conductivity of plaster, compared to traditional cement thermal plaster with lime. From an analysis of the

results merges that, the thermal conductivity of the thermal insulating plaster (VGT_04) is 0.08 – 0.13

W/(mK) range while the reference sample is the 0.25-0.27 W/(mK) range. This means that samples A and B

are 2.5 and 3 times more insulating than the reference sample. It should be emphasized that the results

achieved with these natural aggregates are in line with the literature values [13] obtained for different

aggregates (i.e EPS, cork).

3.3. In field measurements: the case study

In order to investigate the performance of the analysed technology on an actual building, a set of

measurements was performed in a real application on the building envelope of a historic building under

refurbishment in Turin, the ex Albergo di Virtù, 1580 (Fig.4). This historic building, which has a

monumental value for the city of Turin, will become to a top category hotel, reinstating its original function.

The vertical opaque envelope of the building presents a 500 mm thick and heterogeneous (brick and stone)

wall. Thanks to the involvement of the contractor in the project, it was possible during the refurbishment to

use two identical rooms with the same South - East orientation as test rooms. A 60 mm layer of thermal

insulating plaster, made up of Wasselonne natural hydraulic lime and vegetal aggregate materials (VGT_04),

was applied to the wall of a room facing the external environment (Fig.5a); in the other room, the same

external reference wall was left without any internal finishing (Fig. 5b). The air temperature was controlled

in both rooms through electric heaters, with a temperature set point of 23°C.

The thermo-physical behaviour and the energy performance of the vertical envelope was assessed by means

of the continuous measurements of the heat flux, surface temperature and air temperature (according to ISO

9869-1:2014) [14]. The position of the probes was decided after an infrared image campaign of the

investigated walls through a NEC Thermo Tracer (TH9100 MV/WV). In this way, the sensors were

positioned in homogenous and representative areas of the wall (avoiding thermal bridges and discontinuity of

the material). Heat flux meters, which had previously been tested in the laboratory, were placed on the

Page 7 of 24

Accep

ted

Man

uscr

ipt

internal surface of both walls. The internal and external surface temperatures and the indoor and outdoor air

temperatures were measured by means of thermocouples (TT-types, previously calibrated in the laboratory).

The instruments were connected to two data loggers placed in each test room, which retrieved data every 15

minutes. Hourly values were then calculated off-line for the data elaboration.

The thermal performance of the wall with VGT_04 was established, on one hand, through an assessment of

the thermal transmittance and, on the other hand, through the calculation of the daily transmitted energy. The

equivalent thermal transmittance was evaluated through the progressive average methodology, where the

average values, of the specific heat flux (in W/m2) and the temperature differences between internal and

external air, were used instead of the instantaneous values (ISO 9869 1994) [14], according to equation (2).

ns

n

t

AQU

)(

)/(*

[W/m

2°C] (2)

The total daily transmitted energy e24 (in Wh/m2) is defined as the energy transferred through the façade on a

daily basis. The convention used during the measurements was that a negative value of heat flux meant heat

losses and a positive one meant heat gains. The total daily energy (equation 3) was then obtained from the

integral over the 24 h (from 00 am to 00 pm of the following day) of the surface heat flux exchanged on the

indoor surface of the façade.

dtqe

00:24

00:00

24 )( [Wh/m2] (3)

3.4. Infield measurement results

The first step of the infield measurement was an infrared image campaign. It was necessary to verify the

homogeneity of the walls in order to evaluate where to position the sensors. The infrared and visible images

of the two tested walls are presented in Figure 6. The surface temperature is slightly lower in the lower part

of the plastered wall, on the floor and below the window, due to thermal bridges and discontinuity of the

material. The surface temperature of the reference wall is affected to a great extent by the finishing

discontinuity. A central position, where the node with the lateral partition wall did not influence the surface

temperatures, was chosen for the heat flux meter.

The daily energy of a seven days campaign, characterised by a rather high temperature difference between

the indoor and the outdoor environment, is plotted in Figure 7. Boundary conditions, during the selected

Page 8 of 24

Accep

ted

Man

uscr

ipt

days, were similar in the two test rooms. The average air temperature in the room with the thermal plaster

(VGT_04) in the selected days was between 22.6 and 23.6 °C, while an average daily indoor air temperature

of between 22.5 and 22.8 °C was measured in the reference room. A minimum average daily outdoor air

temperature of 11.7 and a maximum value of 17.7 °C were measured in the considered days.

In Figure 7, it is possible to notice that the energy losses through the reference wall are always higher than

those through the wall with the thermal plaster. The measured heat flux values are negative for each day.

Since the outdoor air temperature was always lower than the indoor air temperature, the daily energy that

crossed the reference wall was between 20% (day 3) and 41% (day 7) higher than the daily energy through

the VGT_04 wall. As the boundary condition and the wall structure were the same, it is possible to state that

the difference monitored between the two test rooms was due to the presence of the thermal plaster layer.

In order to have a more complete picture of the energy performance of the tested wall, a new measurement

campaign was carried out in a more representative period, in order to collect enough data to assess the

thermal conductance/transmittance of the wall with the average method. The data collected in this first

campaign, which was performed in a cold April (very cold nights but also sunny days) shows highly

dynamic behaviour of the wall, and it was therefore not possible to define the stationary equivalent thermal

transmittance in a proper way.

The equivalent thermal transmittance of the plastered wall was 0.56 W/(m2K), as shown in Figure 8, which

means a thermal transmittance of the bare wall of about 0.8 W/(m2K), calculated assuming the thermal

resistance of the thermal plaster as resulting from the ratio of the measured value of the thermal conductivity

to the real applied thickness. Unfortunately, it was not possible to measure the bare wall in the other test

room since it was under refurbishment during the second measurement period. The comparison between the

two values confirm that 6 cm of VGT_04 thermal plaster can reduce heat loss by about 30%.

4. CONCLUSIONS

In this paper, thermal insulating plaster has been investigated as a possible option for historic building

refurbishment. A new thermal insulating plaster was obtained adding to the natural hydraulic lime of

Wasselonne, vegetal aggregate materials deriving from the waste of the corn production, which lend higher

mechanical properties to the plaster and allows higher layer thicknesses.

Page 9 of 24

Accep

ted

Man

uscr

ipt

Results concerning laboratory measurement and the monitoring campaign in a real application on the

building envelope of a historic building located in Turin are discussed. The low thermal conductivity of the

new material, which is 2.5/3 times lower than conventional plaster, has led to a significant reduction in the

energy that crosses the wall (about 20% - 40%).

Other analyses are ongoing with the aim of further diminishing this value. However, its good hygrothermal

behaviour and its very low embodied energy already make it a real competitive and marketable solution for

the retrofitting of existing buildings. Future work is necessary in order to evaluate the decay of the

technology in long-term application.

NOMENCLATURE

e24 Wh/m2 daily energy

λeq W/m°C equivalent thermal conductivity

λ W/m°C thermal conductivity

q W/m2 specific heat flux

Q W heat flux

s m thickness

Δts °C surface temperature difference

U* W/m2°C equivalent thermal transmittance

ACKNOWLEDGEMENTS

The research was developed in the framework of the POLIGHT project “SI2 – Sistemi isolanti innovativi”,

funded by the Regione Piemonte. The project was developed in co-operation with DAD_Politecnico di

Torino, VIMARK s.r.l., AGRINDUSTRIA s.n.c., CLUSTER s.r.l., ARTI E MESTIERI and ATC Torino-

Agenzia Territoriale per la casa della provincia di Torino.

REFERENCES

[1] Strategia Energetica Nazionale: per un’energia più competitiva e sostenibile, marzo 2013, approved by

DM 8 march 2013.

[2] ISTAT 2013. Rapporto Bes. Il benessere equo e sostenibile in Italia, capitolo 09, Il paesaggio e

patrimonio culturale, march 2013.

[3] A. Annoni, Scienza ed arte del restauro architettonico. Idee ed esempi, Edizioni Artistiche Framar,

Milano, (1946), p. 14.

Page 10 of 24

Accep

ted

Man

uscr

ipt

[4] K. Fabbri, Energy incidence of historic building: Leaving no stone unturned, Journal of Cultural

Heritage, 14s (2013) e25–e27.

[5] J. Zagorskas, E. K. Zavadskas, Z. Turskis, M. Burinskiene, A. Blumberga, D. Blumbergaba, Thermal

insulation alternatives of historic brick buildings in Baltic Sea Region, Energy and Buildings, 78 (2014) 35-

42.

[6] F. Ascione, F. De Rossi, G.P. Vanoli, Energy retrofit of historical buildings: theoretical and experimental

investigations for the modelling of reliable performance scenarios. Energy and buildings, 43 (2011) 1925-

1936.

[7] L. M. Silva, R. A. Ribeiro, J. A. Labrincha, V. M. Ferreira,. Role of lightweight fillers on the properties

of a mixed-binder mortar. Cement & Concrete Composites, 32 (2010) 19-24.

[8] EN 459-1. 2010 - Building lime. Part 1: Definitions, specifications and conformity criteria.

[9] ISO 14040. 2006 - Environmental management - Life cycle assessment - Principles and framework.

[10] EN 12667. 2001 - Thermal performance of building materials and products - Determination of thermal

resistance by means of guarded hot plate and heat flow meter methods - Products of high and medium

thermal resistance.

[11] ASTM C518. 1991. Test Method for Steady-State Heat Flux Measurements and Thermal Transmission

Properties by Means of the Heat Flow Meter Apparatus.

[12] ENV 13005. 1999. Guide to the expression of uncertainty in measurement.

[13] F. Favoino, M. Perino, V. Serra, Improving thermal performance of plasters by means of recycled and

phase change materials. Proceedings, in: Healthy Buildings 2012, Brisbane (AU), 8 - 12 July 2012, 1-2.

[14] ISO 9869. 1994. Thermal insulation - Building elements - In-situ measurement of thermal resistance and

thermal transmittance.

Page 11 of 24

Accep

ted

Man

uscr

ipt

Table 1, Experimental apparatus (hot plate) specifications

Thermal conductivity range ~ 0.01 - 0.2 W/(mK)

Accuracy ~ 1 %

Reproducibility ~ 0.5 %

Temperature control stability ~ ± 0.03 °C

Thickness measurement precision ~ ± 0.025 mm

Maximum sample size ~ 610 x 610 mm

Actual measuring area 254 x 254 mm

Maximum sample thickness ~ 203 mm

Table 2, Samples of VGT_04 specification

Name Time of

drying

Density Sample size Sample

thickness

[h] [kg/m3] [mm] [mm]

Sample “A” 0 507 600x600 100

Sample“A dry” 48 496 600x600 100

Sample “B” 0 402 300x300 50

Sample“B dry” 48 400 300x300 50

Table 3. Sample VGT_04 A and VGT_04 B thermal equivalent conductivity results for Δt=20°C

Sample A Sample B taverage λeq λeq.dry λeq λeq.dry Δλ

[°C] [W/(mK)] [W/(mK)] [W/(mK)] [W/(mK)] [%]

40.00 0.126 0.105 0.092 0.088 ±2%

25.00 0.115 0.100 0.089 0.086 ±2%

10.00 0.107 0.098 0.086 0.083 ±2%

Table(s) with Caption(s)

Page 12 of 24

Accep

ted

Man

uscr

ipt

List of figure captions

Figure 1. a) Evaluation of the possible thickness for thermal insulating plaster applications (left)

b), Mechanical application of the thermal insulating plaster (right)

Figure 2. a) Thermal plaster sample (left), b) Experimental apparatus: hot plate (right)

Figure 3. Experimental result: thermal conductivity vs average temperature of the plates for samples A and B

of VGT 04, for both humid and dry conditions, and a reference cement thermal plaster

Figure 4, Piazza Carlina Turin, ex Albergo di Virtù during the refurbishment

Figure 5. a) Tested wall with the thermal plaster, b) Reference tested wall

Figure 6. Infrared images: test room with the thermal insulating plaster VGT_04 (upper), and the bare wall of

the reference test room (lower)

Figure 7. Daily energy through the reference wall and the thermal insulating plaster wall

Figure 8. Equivalent thermal transmittance of the tested wall with thermal plaster VGT_04 (b)

List of Figure Captions

Page 13 of 24

Accep

ted

Man

uscr

ipt

1a

Page 14 of 24

Accep

ted

Man

uscr

ipt

1b

Page 15 of 24

Accep

ted

Man

uscr

ipt

2a

Page 16 of 24

Accep

ted

Man

uscr

ipt

2b

Page 17 of 24

Accep

ted

Man

uscr

ipt

3

Page 18 of 24

Accep

ted

Man

uscr

ipt

4

Page 19 of 24

Accep

ted

Man

uscr

ipt

5a

Page 20 of 24

Accep

ted

Man

uscr

ipt

5b

Page 21 of 24

Accep

ted

Man

uscr

ipt

6

Page 22 of 24

Accep

ted

Man

uscr

ipt

7

Page 23 of 24

Accep

ted

Man

uscr

ipt

8

Page 24 of 24

Accep

ted

Man

uscr

ipt

- Thermal insulating plaster is a possible option for historic building refurbishment

- A new thermal insulating plaster vegetal based is investigated in the laboratory and infield on a real

historic building

- Vegetal aggregate materials lend higher mechanical properties to the plaster and allows higher layer

thicknesses

- The low thermal conductivity of the new material led to a significant reduction in the energy that

crosses the wall

*Highlights (for review)