mc wall mc600 2013/52 - smart systems

MC WALL 2008/31 MC600 2013/52

CWCT CERTIFICATION CURTAIN WALL DESIGN AND INSTALLATION

CWCT Technical Seminar

Dr Stephen Ledbetter CWCT

Curtain wall Design and Installation

Part 1 – Construction Window and Screens NHBC definitions and Requirements

Part 2- Performance Structural Suitability

Deflection limits Loads Watertightness/Drainage Air Permeability Testing

Part 3- Interfaces Design Performance Cavity Walls Water/Air/Vapour Barrier

Technical Workshops

Richard Willets Tremco Key Account Manager for the WF&S Division

Tremco Illbruck Limited Hindley Green, Wigan WN2 4HT T: 01942 251400 F: 01942 251410 M: 07801 541187 [email protected] www.hilti.co.uk

Cinzia Bassan Specification Engineer at Hilti

Hilti (Gt. Britain) Ltd Trafford Park, Manchester M17 1BY T: 0800 886 100 F:0800 886 200 M: 07525 904701 E [email protected] www.hilti.co.uk

Paul J Anderson Guardian Architectural Specifications Manager

Guardian Industries UK LTD Goole, East Yorkshire DN14 8GA T: 01405 726800 F: 01405 726999 M: 07712 76464

mailto:[email protected]

http://www.hilti.co.uk/

http://www.hilti.co.uk/

Smart systems in house course

1

Glazing system requirements

Scope of today’s talks

• When is a window not a window?

• NHBC definitions and requirements

• Performance of more complex glazing schemes

• Interfaces

NHBC

• National House Building Council

• Provides new home warranties

• Leading provider in the UK

• Sets standards and gives a 10 year warranty

• Standards;– 6.7 Windows, doors and glazing

– 6.9 Curtain walling and cladding

NHBC requirements

• A full set of drawings

• A schedule of revisions

• Manufacturer’s specification

• Specific details of interfaces

• Fixing schedules

• Manufacturer’s details

• Details of on-site testing regime

• No possibility of:

– Site based design

– Ill considered details

– Bluffing

– Avoiding testing


2

NHBC requirements

• Certification

– CE Marking

– Kitemark

– BBA

– CWCT

• Made available to NHBC prior to construction

• Used as reference material

• The system should be used within the scope of the certification

Windows

• Building component for closing an opening in a wall that will admit light and may provide ventilation,

• Factory produced unit that has one or more openings bounded by a perimeter frame.

Windows

• Performance of a window normally assessed as an independent unit,

• Installer needs to ensure interfaces provide adequate performance.

Window assembly or screen

• Combination of components to give a larger area of glazing.

• Not a curtain wall


3

Window assemblies

• Construction of windows and horizontal or vertical joining bars

• May be disassembled to give stand-alone windows

Window assemblies

• Joining bars take many forms

• They have to support the window• They have to make the air and water seals

• It is helpful if they allow for tolerances in manufacture and construction work.

Glazing screen

• Glass supported to provide a glazed screen

• When disassembled it comprises glass or glazing units and framing / support components

Glazing screen

• Glazing screens range from simple shop front technology with shuffle glazing to more complex bolted and bonded glazing systems


4

EN 14351 – Window product standard

• Screen– Assembly of two or more

windows with or without separate frames

• The test for watertightnessand weathertightness shall be carried out on the screen or its individual components

• Watertightness– performance shall be

determined by the part with the least favourable performance

• Air permeability– The air permeability shall be

the sum of the air permeability of the individual parts and the joints

Types of window assembly

• Horizontal ribbon one window high,

• Vertical ribbon one window wide,

• May be assessed as a window but need to include jointing detail for;– Weathertightness,– Structural integrity may

be required,– Thermal performance

must be checked.


• Storey height assembly more than one window in each direction,

• May be assessed as a window but need to include jointing detail for;– Weathertightness,– Structural integrity,– Thermal performance

must be checked.


• Assembly more than one window in each direction that passes in front of floor slab,

• Assessed as a curtain wall.


5


Mount Pleasant, London

Stick system curtain wall

• System of framing members used to form a grillage,

• Commonly aluminium but steel used for fire resistance,

• Design of system includes gaskets and jointing details,

• Opaque and transparent infills glazed-in used to complete wall.

Stick wall

• Components selected to meet requirements of project,

• Framing members delivered to site as pre-cut and machined sections,

• Frames fixed to floor slab/structure,

• Opaque and transparent infills glazed-in.

Windows in curtain walling

• As required for ventilation and cooling

• ‘Pick n mix’ approach by architects

• Tried and tested combinations?

Lucy’s Oxford


6

Rainscreen walls

• Multi-layer construction;– Rainscreen panels,– Air gap,– Airtight backing wall,– Insulation,– Water proof membranes,– Vapour control layers,

• Windows fixed in openings in wall,

• Materials vary from system to system, but principles remain the same.

Backing wall

• Solid backing wall;– Masonry,– Concrete,

• Framed;– Site assembled,– Prefabricated.

Reasons for using rainscreen walls

• Architectural intent:– Larger opaque areas,– Wide range of materials,

• Wide range of cost,

• Used for both new-build and refurbishment/repair projects.

Consequences of using rainscreen walls

• Wall split into packages– Coordination of packages

required,• Standard components but

performance depends on interfaces,

• External access required,• Craneage depends on

degree of prefabrication,• Completion of back wall and

windows can allow internal work to proceed during rainscreen erection.


7

Windows in rainscreen walls

• High-rise layered wall construction

• ‘Punched’ window openings

• Windows installed on-site or off-site?

Brook House , Tottenham


1

Performance of window assemblies, screens and curtain walls

Structure

• Window assemblies comprising more than one tier and more than one window wide require structural framing members

• Screwing window frames together does not give stiffness

Structure

• Ribbon glazing with a single tier of windows may require stiff vertical joining bars

• Windows are generally designed and tested to be fitted in a stiff opening (A hole in a wall or a four edge support in a test cabinet)

• Fixing window frames on only the top and bottom edges will allow the windows to deflect more potentially impairing the glazing seals and the sealing of opening lights.

Deflection limits - General

• Excessive deflections can impair performance of gaskets and seals

• Strongly deflected glazing can cause feelings of discomfort as well as producing distorted reflections. Visual distortion is controlled by limits on deflection measured between points of support.


2

Deflection limits - General

• Mullions:Out-of-plane

– Length ≤ 3000 mm δ ≤ H/200– 3000 < length < 7500 δ ≤ 5+H/300– 7500 ≤ length δ ≤ H/250

– Limit of H/300 sometimes specified for structural sealant glazing. This limit applies to the SSG carrier frame between fixings to the mullion not to the mullion.

Local deflection

• The design of the infill normally assumes continuous support along the edge of the panel. To provide support the framing must be stiffer than the panel it supports. Deflection limits vary with the type of infill and are related to the length of the supported edge.

Deflection limits - Local

• Framing members with single glazing:– 1/125 of length along pane edge,

• Framing members with double glazing:– 1/175 of length along pane edge,

• Rainscreen panels:– 1/90 of span between points of attachment for aluminium,

glass or steel,– 1/360 of span between supports for stone.

Serviceability deflections (in-plane)

• Overall deflection of framing members:– Limited to:

• prevent glass contact,• prevent drainage failure,• maintain bite on glass,

– 1/500 or 3mm, – Primarily for transoms.


3

Loads (actions)

• Dead load, • Wind load,• Live load:

– Occupancy loads,– Access loads,– Snow loads,– Other loads,

• Induced loads,

• Impact.

Dead load

• EN 1991-1-1• Eurocode 1: Actions on

structures - Part 1-1: General actions - Densities, self-weight, imposed loads for buildings,– Glass 25kN/m3,– Aluminium 27kN/m3,– Steel 77 to 78.5kN/m3,– Normal weight concrete

24kN/m3.

Occupancy loads

Vertical loads• Not given in EN 1991-1-1• PD6688-1-1 gives non

contradictory complementary information for use in the UK and requires a vertical load of 1kN or 0.6kN/m on parapets

• CWCT requires:– 1 kN or 0.6 kN/m

Barrier loads• EN 1991-1-1• Height above floor level mot

more than 1200mm (1100mm in UK)

• Loads of:– 0.2 to 5.0 kN/m

Depending on occupancy,– 0.5 recommended for

offices,– NA gives same values as

BS 6399,– PD 6688-1-1 gives

distributed and point loads on infill.

Horizontal barrier loads

Line loadkN/m

UDLkN/m2

Point LoadkN

Residential 0.36/0.74 0.5/1.0 0.25/0.5

Office 0.74 1.0 0.5

Liable to crowding

1.5/3.0 1.5 1.5

Retail 1.5 1.5 1.5


4

Access loads

• Cradle loads

• A resting cradle is covered by the load opposite

• Larger loads may arise from collisions. These may be considered as:– Impact loads– Accidental loads

• General loads due to maintenance:– 500 N on a 100 mm square

Out-of-plane loads

• Access loads are less than the wind load for all but the smallest panels and therefore not a critical load on the frame,

• However, the panel itself should be checked for resistance to access loads,

• Barrier loads may be applied to the infill or transoms.

Snow load

• Standards:– BS 6399, Part 3,

– EN 1991-1-3 • Eurocode 1: Actions

on structures - Part 1-3: General actions -Snow loads

– Local snow code,

• Snow may settle on:– Ledges– Roofs– Canopies– Brise-soleil

• Snow load has a longer duration than wind load and cannot be added to wind load for design of glass (BS5516 applies a factor of 2.6 to snow and dead load).

Transferred loads

• Loads from additional elements:– Brise-soleil– Canopies– Signage– Etc..

– Fit-out.


5

Transferred loads

• Loads from additional elements:– Self-weight– Wind– Snow– Access

Induced loads

• Thermal loads;– Restrained thermal movement gives rise to potentially high

stresses and loads,

• Lack-of-fit;– Members that are forced to fit will:

• Carry some of the forcing load after fitting,• Impose additional loads on fixings and adjacent parts,

• Load pick-up;– Inappropriate connections may transfer load from the primary

structure to the building envelope components.

Watertightness

• Individual windows may have drained frames

• The joining bar seal may be imperfect and water passing this has to be drained

• Drainage from the window frame may be combined with drainage from the joining bar to reduce the number of openings

Drainage slots inpressure plates

Drainage slots incover caps

Setting blocks mayobstruct drainage

Drainage at transom


6

McAlpine 2008

Drainage to ends

• Setting blocks may obstruct drainage,

• Drainage paths may be very long,

• Where does the water go next?

Air leakage

• Need to know;

– Test pressure,

– Allowable leakage (if different from default values in Standard),

– Infiltration/exfiltration.

Air permeability

• Infiltration:– Normal basis of

classification,– Test at 300,450 or 600 Pa,

• Exfiltration:– Required as whole building

tests use exfiltration,– Test up to 100 Pa,– Specifier to state acceptable

air leakage,– Normally the same as for

infiltration at 100 Pa.

Water leakage

• Need to know:– Test pressure,– Whether dynamic test required,

• Water run off from large impermeable areas is great:– Test using 3.4 l/min/m2 (CWCT/AAMA),– Test using 2.0 l/min/m2 (CEN).


7

Proprietary stick system wall Test procedures

• Pressurise box,

• Water spray,

• Measure;– Air pressure,– Air leakage,– Water flow,– Deflections.

Preparation

• Erect by installation team,

• Allow curing time,

• Clean thoroughly.

Water tightness - dynamic pressure

• Aeroplane engine;– CWCT,– AAMA,– Limited by CE rules,

• European test;– Roving fan,

• CWCT Standard;– Mandatory for 600Pa and

above,– Optional below 600Pa.


8

Dynamic testing - fan

• EN 13050

• Optional test in EN framework,

• Allowed for face sealed curtain walls,

• Difficult to use with Brises soleil etc.

Other details that may affect application of test results

• Thickness of gaskets,• Jointing of gaskets,• Stiffness of glazing units,• Inserts in glazing rebates,• Movement joints,• Opening lights,• Different methods of glazing,• Different methods of

drainage;– Transom– Mullion,

• Different width of framing member,

• Components not supplied by system company,

• Workmanship,• Support conditions,• Interface details.

Different thickness gaskets Different methods of glazing


9

Windows and doors

• May be tested in accordance with window/door standards;– Does not include sills or interface details,– Deflection of curtain wall may impair seals of window,– Need to check performance level,

• May be included in curtain wall test,– Opening joints often taped up but allows testing of interface,

• The decision depends on:– Size of contract v cost of testing (risk),– Availability of previous test results for combination,– Evidence of previous use of combination,– Evidence available from alternative suppliers.

Site tests

• Inspection,

• Hose test,

• Spray bar test,

• Cabinet test,

• Whole building air leakage,

• Thermography.

Hose test Hose test - joint type

• Method is intended to test workmanship of site-sealed joints, i.e. Quality of sealant application and quality of gasket installation,

• May not be appropriate for joints in porous materials,

• Open (i.e. unsealed) joints should not be subjected to hose test,

• For rainscreen walls testing interfaces prior to rainscreen installation may be appropriate,– Spray bar probably more appropriate.


10

Hose test - joint type

• Openable joints can be subjected to hose test but method may need to be revised,– Joints which compress a

gasket likely to satisfy test,

– Joints which rely on a flipper gasket more likely to fail under test,

• NHBC Standard does not refer to testing opening joints.

Hose test - calibration

• If a laboratory test is carried out then hose test the same specimen to prove validity of test,

• If necessary, test openable joint at reduced water pressure:– Test opening joint at low water pressure, progressively

increasing pressure until joint fails,– Use last successful water pressure for remaining tests,

• If a laboratory test is not carried out then calibrate hose test using opening light with acceptable workmanship.

Spray bar

• European Standard (BS EN 13051:2001),

• Spray water from pipe with nozzles at uniform intervals:– Nozzles at 400 mm

centres and 250 mm from cladding surface,

– Flow rate equivalent to 5 litres/min. per m.

• Suitable for all joints providing water is not sprayed directly at joints.

Spray bar - method

• Objective is to simulate water running down face of cladding,– useful where there are penetrations through the cladding.

• Set spray bar up between 250 - 400 mm above area to be tested, which may be considered to be no more than 3.5 m below spray bar,

• Allow water to run down over face of cladding,

• Spray for 30 minutes, then turn off spray and continue to observe for 30 minutes,

• If failure occurs then lower spray bar to bottom of area and progressively work up.


11

Spray bar - joint type

• Open and operable joints should still pass:– providing water is not sprayed directly at joints.

Cabinet test

• Procedure similar to laboratory test,

• Fix pressure box to one side of sample:– Can use polythene sheet

and vacuum pump,– Must ensure sheet

doesn’t draw onto cladding,

• Spray water onto exterior face.


1

Window interfaces

Performance at interfaces

• Sealing:

• Dual seal recommended,– Outer primary water seal,– Drained cavity,– Inner seal provides

secondary water seal and air seal,

• Vapour seal?

• Other:

– Thermal bridging,– Transfer of loads,– Tolerance,– Movement,– Sound,– Fire,– Buildability,– Maintainability.

Windows in cavity walls

• The window may be fixed;– Flush, or almost with the outer face,– Flush, or almost with the inner face,– In, or near to, the plane of the cavity.

• This requires attention to detailing;– Damp proof membranes,– Sills and flashings,– Cavity closers,– Window pods. In outside

leafAcross the cavity

In inside leaf

To outside leaf

Position within facade

Sloping sill


2

Position within facade

• Positioning near the mid-plane:– Gives some weather protection by recessing the window– Allows continuity of thermal insulation.

• Positioning in the outer face is common with insulated panel systems.

• Positioning in the inner face is common with rainscreen walls.

Water barrier

• The water barrier comprises;– Breather membrane,– Flashing at head,– Window,– Window cill,– Breather membrane.

Air barrier

• The air barrier comprises;– Dry lining,– Head fit-out,– Window,– Window board,– Dry lining.

Vapour barrier

• The vapour barrier comprises;– Dry-lining,– Head fit-out,– Window,– Window board,– Dry lining.


3

Water and air barriers in rainscreens

Construction Water barrier Air barrier

Rainscreen window pods

• In a rainscreen wall a window pod of pressed metal or moulded plastic provides a water barrier

• It is integrated with the rainscreen panels and sealed to the window.

Curtain wall or screen to insulated render Curtain wall or screen to brick block wall


4

Curtain wall or screen to soffit Curtain wall or screen to balcony

Window to insulated render system Window interface in built up wall


5

Curtain wall/Brickwork interface

Window in precast concrete panel


6

Window cills

• Window cills serve three purposes, they;– Are a decorative feature concealing the window to wall joint,– They shed water so that it falls clear of the wall,– They, along with any cavity flashings, intercept all water in

cavities within or adjacent to the window that would otherwise run into the wall.

• Water may drain out of the base of the window frame, either through drainage openings or unintentionally through fixing holes. This should be intercepted and drained by the window sill.

Window cills

• Window cills should have a sloping top surface, 2o – 7o, so that water runs from them by gravity.

• This looks fine on the drawings but in practice water will also be driven along the cill by the wind. In this case water may flow over the end of the cill and drip into the wall.

• This is prevented by having an upstand at the end of the cill. Many standard cills comprise prismatic extruded profiles. However, some have end fitments to create a upstand.

Three dimensional flow


7

Structural aspects of interfaces

• Loads;– Self-weight– Wind-loading,– Snow loads,– Access loads,– Impact and similar loads,– Other applied loads.

• Movement;– Movement of the wall,– Expansion/contraction of

the window or door.

Load transfer

• All of the loads on a window or door have to be transferred to the supporting wall by the brackets and fixings.

• It is important that the brackets and fixings are capable of carrying these loads.

• The strength of the fixings will depend on the substrate into which they are fixed and the depth of embedment;– Lightweight and hollow blocks give the greatest concern

when considering the strength of fixings.

Self-weight loads

• These forces depend on the size of a window or door and also the thickness of the glass used.

• For example a glazing unit of size 1800 x 1200 mm and comprising 10-12-4 glazing will weigh 94.5 kg.

• Traditionally windows have been mounted in the plane of the wall and these loads have been carried by bearing the cill on the wall.

• With rainscreen and similar types of wall the window sits out of the plane of the wall and the brackets act as cantilevers.

Self-weight loads

• In-plane loads only.• Loads carried by bearing on a

packer.

• Out-of plane loads.• The cantilever bracket will be

subject to bending like a shelf bracket.


8

Wind loads

• Wind loads on windows and doors in the UK range from 600 -2400 Pa depending on;– Location,– Building size and shape.

• For a window 1800 x 1500 mm the wind load will be in the range 157 – 630 kg.

• This is far greater than the self-weight loads.

• The wind load may be positive or negative.

Impact and similar loads

• These are loads caused by;– Accidental human impact,– Moderate and anticipated abuse such as individuals climbing

through windows.

• For windows that are robust against wind load the fixings are normally strong enough to carry these loads.

• If large impact loads are anticipated or the window is intended to be blast resistant then fixings of greater strength will be required.

Other applied loads

• Any components fixed to a window or cladding panel will cause additional loads that have to be carried by the fixings. These include;– Brises soleil,– Signage,– Light fittings,– Aerials and satellite dishes.

• The resulting loads will comprise not only the self-weight but also any additional wind or snow load.

Fixings and brackets

• Windows should be fixed using adequate fixings at appropriate positions and spacing.

• These should be shown in system design manuals.

• The size and type of fixing will depend on the type and strength of block or concrete into which it is fixed.

• Additional fixings, deeper fixings or fixings of a different type may be required when fixing to very light-weight or hollow blocks.


9

Movement

• Window and door frames expand and contract as the temperature changes.

• It is important that windows are fixed in a way that allows this movement to occur.

• This is best achieved by not placing fixings near to frame joints as framing members will shorten during cooling and joints may fracture when pulled in tension.

Movement

• Do not place fixings in the zones indicated.• Follow system instructions.

Interface design – thermal bridging Interface design – thermal bridging

• Significant thermal bridge,– Serious internal surface

condensation.• Not a problem with the window

system,• The issue is the interface design

(non-standard),• Only solution without removing the

window was to try and insulate the reveal by adding an external pressing,

• Not ideal as only a very thin layer of insulation could be added.


10

Interface design

Only 10mm – limited performance.

Interface design

Original design

Modified design-Limited improvement

Reveal pressing

Interface design

• Another example of a window to built-up wall interface,– Window pod forms

thermal bridge back to steel framed wall.

Thermal bridge

No thermal break Very cold ~ 5°C

Interface design – thermal bridging

• Original design.


11

Warmer temperatures within wall~ 10°C

Interface design

Thermal break

• Modified design.

Membrane air seals

• These are critical to whole building air leakage rates

• Bonding is highly dependent on good workmanship

• Use a strip to clamp the membrane when bonding to:– Any soffit– Any surface that will give

low adhesion


1

Window interface in built up wall


2

Curtain wall/Brickwork interface


3


4

Window in precast concrete panel


5


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