Design and Detailing for Airtightness

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Acknowledgements

The author, Chris Morgan of Locate Architects, would like to thank the following people for their invaluable contribution to developing this guide:

Steering Group:
Jim Mitchell, Architecture Policy Unit, Scottish Executive
Mike Thornton, Energy Savings Trust
Misia Jack, Scottish Federation of Housing Associations
Fionn Stevenson, EDG (Ecological Design Group), Dundee University / SEDA (Chair)

Advisory Group:
Finlay Black, Tulloch Construction
John Gilbert, John Gilbert Architects
Paul Jennings, Stroma Technology
Liz McLean, East Lothian Council Architecture Department
David Olivier, Energy Advisory Associates
Paola Sassi, Cardiff University
Ian Walker, Communities Scotland
Peter Warm, WarmHomes

Production Assistance:
Parr Architects, Edinburgh
Ralph Ogg & Partners, Perth
Building Performance Group, London

My thanks also go also to the numerous individuals in the manufacturing and construction industry who have specifically helped to develop the details in this guide through freely giving their advice and information.

SEDA gratefully acknowledges the funding from the Scottish Executive’s Sustainable Action Grant which made this guide possible.

Acronyms

ATTMA - Air Tightness Testing and Measurement Association
BPEO - Best Practical Environmental Option
BRE - Building Research Establishment
BS EN - British Standard European Norm
CIBSE - Chartered Institute of Building Service Engineers
CIRIA - Construction Industry Research and Information Association
EC - European Community
EU - European Union
NBS - National Building Specification
NGO - Non-governmental Organisation
RIAS - Royal Incorporation of Architects in Scotland
RIBA - Royal Institute of British Architects
SEDA - Scottish Ecological Design Association
SEPA - Scottish Environmental Protection Agency
UKAS - United Kingdom Accreditation Service

References

Web based Information

General Information
(much also to be found on Company websites noted below)

Air Infiltration and Ventilation Centre
32 2 655 77 11 (Holland) (Operating Agent is INIVE, contact Dr. Peter Wouters, there is no participating agent in the UK)
http://www.aivc.org/ or http://www.inive.org

CIBSE (Chartered Institution of Building Services Engineers)
0208 675 5211 (London)
http://www.cibse.org/

BSRIA Ltd.
01344 465 600 (Berkshire)
http://www.bsria.co.uk/

Research Council Canada: Institute for Research in Construction
http://irc.nrc-cnrc.gc.ca/irccontents.html

UK Companies Specialising in Airtightness Testing etc.

Stroma Technology Ltd.
01924 870 677 (West Yorkshire)
http://www.stroma-ats.co.uk

Building Envelope Technologies
(00353) 055 28869 (Co. Wexord, Eire)
http://www.betechnologies.ie/page6.html

BSRIA Ltd.
01344 465 600 (Berkshire)
http://www.bsria.co.uk/

HRS Services Ltd.
0114 272 3004 (Sheffield)
http://www.air-tightness.co.uk/

Chiltern Dynamics
01494 569 830 (Buckinghamshire)
http://www.chilterndynamics.co.uk/airtightness_framer.htm

BRE
01923 664 500 (Watford)
http://www.bre.co.uk/service.jsp?id=134 or
http://projects.bre.co.uk/envdiv/airtight/index.htm

Wintech Test Engineering
01952 586 580 (Shropshire)
http://www.wintechairpressuretesting.co.uk/

Steel Construction Institute
(Testing of Construction Types rather than whole Buildings)
http://www.steel-sci.org/consultancy/Thermal/default.html

Published Information

Standards and Regulations

British Standards Institution

BS EN 13829: 2001 Thermal performance of buildings: Determination of buildings - fan pressurization method
BS 4255: Rubber used in preformed gaskets for weather exclusion from buildings Part 1: 1986 Specification for non-cellular gaskets .
BS 4873: 1986 Specification for aluminium alloy windows
BS 5368: Methods 01 testing windows Part 1: 1976 (EN 42) Air permeability test
BS 5925: 1991 Code of practice for ventilation principles and designing for natural ventilation
BS 6375: Performance of windows: Part 1: 1989 Classification for weathertightness (including guidance on selection and specification)
BS 6510: 1984 Specification for steel windows, sills, wind0w boards and doors
BS 7386: 1997 Specification for draughtstrips for the draught control of existing doors and windows in housing (including test methods)
BS 7412: 1991 Specification for plastics windows made from PVCu extruded hollow profiles
BS 8200: 1985 Code of practice for design of non-loadbearing external vertical enclosures of buildings

International Organisation for Standardisation (ISO)

ISO 6589: 1981 Nr permeability of joints, watertightness
ISO 6613: 1980 Nr permeability of tests on windows and doors
ISO 9972: 1996 Thermal Insulation – Determination of building airtightness – fan pressurization method

Building Regulations

Conservation of Fuel and Power
England and Wales. Approved Document L2. 2002 edition.
Northern Ireland. Part FF of the Building Regulations (Northern Ireland). 1990.
Scotland. Part J of the Technical Standards for Compliance with the Building Standards. 1990.

Ventilation
England and Wales. Approved Document F.1995 edition.
Northern Ireland. Part K of the Building Regulations (Northern Ireland). 1990.
Scotland. Part K of the Technical Standards for Compliance with the Building Standards. 1990.

Offices, Shops and Railway Premises Act 1963.

By Specific Organisations

Chartered Institute of Building Services Engineers (CIBSE)

Testing buildings for air leakage. CIBSE Technical Memorandum TM23, London, 2000.
Building energy code. Part 2 (a) Calculation of energy demands and targets for newly built, heated and naturally ventilated buildings

BRE

BRE Reports
BR 154 Improving the Habitability of large panel system dwellings. 1989
BR 162 Background Ventilation of Dwellings: A Review, 1989
BR 262 Thermal Insulation: Avoiding Risks. 2002
BR 359 Airtightness in UK Dwellings: BRE’s test results and their significance. 1998
BR 448 Airtightness in Commercial and Public Buildings 2002

BRE Digests
306 Domestic Draughtproofing: Ventilation Considerations
350 Climate and site development
Part 1: general climate of the UK
Part 2: influence of microclimate
Part 3: improving microclimate through design
398 Continuous mechanical ventilation in dwellings: Design Installation and Operation
399 Natural ventilation in non Domestic buildings

BRE Good Building Guide
32 Ventilating thatched roofs

BRE Good Repair guide
21 Improving ventilation in housing

BRE Information Papers
14/79 Resistance to Air Flow through External Walls
6/89 Use of BREFAN to Measure the Airtightness of Non-domestic Buildings
5/95 Testing the performance of terminals for ventilation systems, chimneys and flues
6/95 Flow resistance and wind performance of some common ventilation terminals
13/95 The passive gas tracer method for monitoring ventilation rates in buildings
4/98 Night ventilation for cooling office buildings
12/98 Trickle ventilators in offices
4/99 Ventilators: ventilation and acoustic effectíveness
5/99 Humidistat-controlled extract fans
1/00 Airtightness in UK Dwellings
12/00 Positive input ventilation in dwellings
9/04 Maintaining good air quality in your home

Energy Efficiency Office

A list of publications related to energy conservation and management in
commercial and public buildings is available from BRECSU at BRE.

Metal Cladding and Roofing Manufacturers Association.

Guidance for the design of metal cladding and rooting to comply with AD L2. Tech. Note 14, 2002 Edition.

AIVC (Air Infiltration and Ventilation Centre)

Lecompte J G N. Airtightness of Masonry Walls. Proceedings of the 8th AIVC Conference Uberlingen, Germany 1987

Liddament M W. A guide to energy efficient ventilation. 1996.

Limb M J. Air infiltration and ventilation Glossary. Technical Note 36. 1992.

Limb M J. Ventilation and Building Airtightness: an international comparison of Standards, Codes of Practice and Regulations. Technical Note 43. 1994.

Shaw C Y & Brown W C. Effect of a Gas Flue Chimney on the Air Leakage Characteristic of a Two-storey House. Proceedings of the 3rd AIVC Conference London, UK 1982

Sherman M & Dickerhoff D. Airtightness of US Dwellings (Lawrence Berkeley Laboratory Report No. 35700) Proceedings of the 15th AIVC Conference, ppv236-234. 1994

General

Bankvall, C. Thermal transmittance of building envelope as influenced by air infiltration and workmanship, in Proc. Conf.Energy Conservation and the Built Environment,Vol III 3.152-31.63. 1982

Bordass W. Envelope Airtightness. Architects’ Journal, pp48-51, 13th April 2000

Carlsson, B., Elmroth, A. & Engvall, P.A. Airtightness and Thermal Insulation: Building Design Solutions. Stockholm, Statens Råd för Byggnadsforskning.1980

Dickson D J. Air Flow through and Within Masonry Walls. The Electricity Council Research Centre (now EA Technology) Memorandum ECRC/M1420, Capenhurst UK 1981

Doran, S. 2003 Improving the thermal performance of buildings in practice, BRE Project Report 16476.

Elmroth A. Build Tight – Ventilate Right. Air Infiltration Review, Air Infiltration Centre, Bracknell UK 1980

Elmroth A. et al, Airtightness and Thermal Insulation: Building Design Solutions. Swedish Building Research Council 1980.

Elmroth A & Lodgberg A. Well Insulated Airtight Buildings, Energy Consumption, Indoor Climate, Ventilation and Air Infiltration. Proceedings of 8th CIB Congress, Oslo 1980

Eyre, D, Air-Vapour Barriers, Saskatchewan Research Council Jan 1983

Gaze A I. Airtightness of Timber Frame Housing: Tests to Assess Methods of Reducing Air Leakage for Typical Joints. TRADA Research Report 14/86, High Wycombe UK 1986

Hens, H., Janssens, A. & Deprataere, W Cavity walls with high insulation quality: performance prediction using calculation procedures and field testing, IEA Annex 32, IBEPA. 1999

Hruby V & Svendsen S. Airtightness Control of Single-Family Houses. Building Physics 2002 – 6th Nordic Symposium, Session 20: Building Design and Technology 2 pp.837-842 2002

Jennings P. Airtightness in buildings. (Parts 1 & 2) Building for a Future magazine Winter 00/01, Spring 01

Kim A & Shaw C Y. Seasonal Variations in Airtightness of Two Detached Houses. ASTM Symposium on Measured Air Leakage of Buildings, Philadelphia, USA, 1984

Kronval J. Testing houses for air leakage using a pressurization method. ASHRAE transactions, Vol 84, Part 1, 1978

Lecompte, J. The influence of natural convection on the thermal quality of insulated cavity construction, Building Research and Practice, CIB. 1990

Lowe R J, Curwell S R, Bell M & Ahmad A. Airtightness in Masonry Dwellings: Laboratory and Field Experience. Building Services Engineering Research and Technology 15(3), pp 149-155, 1994

Lowe R: Impacts of construction defects on heat loss and CO2 emissions from dwellings. Leeds Metropolitan University - Student Handout (0113 283 1717) Dec. 2003

Meier A. Infiltration: Just ACH50 Divided by 20? Home Energy, pp 35-37, Jan./Feb. 1994

Perera E & Parkins L. Build Tight – Ventilate Right. Building Services, CIBSE June 1992

Persily A K. Envelope design guidelines for federal office buildings: thermal integrity and airtightness. National Institute of Standards and Technology. US Dept. of Commerce, 1993

Potter I N. Airtightness Specifications. BSRIA Specification 10/98, BSRIA Bracknell 1998

Potter I N. Envelope Integrity Demonstration Studys. BSRIA Technical Note TN/99, BSRIA Bracknell 1999

Saxhof B et al, Insulation and Airtightness of Six Low Energy Houses at Hjortekaer, Thermal Insulation Laboratory, Danish technical University Noember 1982

Shaw CY, Reardon JT and Cheung MS. Changes in air leakage levels of six Canadian office buildings. ASHRAE Journal, 1993

Shaw C Y, Gasparetto S & Reardon J T. Methods for Measuring Air Leakage in High Rise Apartments. ASTM Special Technical Publication STP 1067 Philadelphia, USA, 1990

Sherman M. Estimation of Infiltration from Leakage and Climate Indicators. Energy and Buildings 10, ’87

Siviour J B. Plasterboard Fixing for Thermal Integrity. The Electricity Council Research Centre (now EA Technology) Memorandum ECRC/M2238, Capenhurst UK 1988

Siviour, J.B. Experimental U-Values of Some House Walls. Building Services, Engineering, Research & Technology 15 (1). 1994

Scivyer C, Perera E & Webb B. Build Tight: The Orkney Experience. Building Services, CIBSE, July 1994

Socolow, R.H. 1978 Saving Energy in the Home: Princeton’s Experiments at Twin Rivers, Princeton University Press.

Uvslokk, S. The importance of wind barriers for wood frame construction. in 8th AIVC conf, Ueberlingen DBR, September. 1987

Glossary

This glossary has been developed to be as consistent as possible with those defined in Technical Note AIVC 36 Air Infiltration and Ventilation Glossary

Air barrier
An air barrier comprises materials and/or components, which are air impervious or virtually so, separating conditioned spaces (heated), from unconditioned spaces (unheated).

Air change rate
The rate at which outside air enters a space divided by the volume of that space. This is expressed as ach (air changes per hour).

Air curtain
A stream of high velocity, temperature-controlled air which is directed across an opening. It enables control of conditions in a space, which has an open entrance.

Air exfiltration
The uncontrolled outward leakage of indoor air through cracks, discontinuities and other unintentional openings in the building envelope.

Air infiltration
The uncontrolled inward leakage of outdoor air through cracks, discontinuities and other unintentional openings in the building envelope.

Air leakage audit
The inspection of materials and components, between conditioned and unconditioned spaces to try to establish where major discontinuities in an air barrier system might exist.

Air leakage index
The leakage of air (m3.h-1) in or out of a building space, per unit area (m2) of envelope (excluding ground floor area ,except for non-ground supported lower floors) at a reference pressure of 50 Pa between inside and outside the building.

Air permeability
The leakage of air (m3.h-1) in or out of a building space, per unit area (m2) of envelope (including ground floor area) at a reference pressure of 50 Pa between inside and outside the building.

Air leakage rate
The leakage of air (m3.h-1) in or out of a building space, per unit volume (m3) at a reference pressure of 50 Pa between inside and outside the building.

Air leakage path
A route by which air enters or leaves a building or flows through a component.

Airtightness
A term describing the leakiness of a building. The smaller the leakage for a given pressure difference across a building, the tighter the building envelope.

Airtightness layer
A layer built in to the external envelope to minimise air infiltration/exfiltration. It may consist of a wide range of materials (for example,sealants, gaskets, glazing or membranes) and should be continuous to be effective.

Breather membrane
A water-resistant sheet which allows transmission of water vapour, but which provides resistance to airflow.

Conditioned zone
The occupied zone in a building requiring heating or cooling and normally bounded by an airtightness layer.

Draught
Excessive air movement within the conditioned zone, which may cause discomfort.

Draughtproofing
Filling gaps between opening parts of components and their frames.

Envelope area
The boundary or barrier (m2) separating the interior volume of the building from the outside environment. This includes the area of the external walls, roof and depending upon the air leakage parameter specified the area of the ground supported floor.

Fan pressurisation test
A method of testing air leakage of a building. It allows airflow and pressure difference across the envelope to be measured and an estimate of leakage to be obtained.

Infiltration rate
The rate at which outside air infiltrates a building or a room under natural meteorological conditions (normally expressed in air changes per hour or litres per second)

Infrared camera
A camera sensitive to the infrared part of the spectrum, which can be used to ‘see’ locally cooled areas on the internal surfaces or heated areas on internal and external surfaces of the envelope of a building.

Minimum ventilation requirement
The minimum quantity of outdoor or conditioned air which must enter a building to maintain an acceptable indoor air environment for occupants.

Natural ventilation
The movement (caused by wind and outside temperature) of outdoor air into a room or space through intentionally provided openings, such as windows and doors and non-powered ventilators.

Smoke test
A building (or parts of it) is filled with smoke using smoke machines and then pressurised to force the smoke through gaps in the building envelope.

Smoke tube/pencil
A hand held device which produces smoke in small quantities for more specific identification of leakage paths within a building under pressurisation or depressurisation, or under natural infiltration.

Stack effect
Air movement through a building caused by differences in the density of air due to temperature differences between the air inside and outside of the building.

Thermography
The use of cameras sensitive to infrared radiation to identify thermal weak spots in the envelope of the building and to help identify air leakage paths through gaps and cracks in the building.

Vapour control layer
A layer impervious to water vapour and usually enclosing an occupied space.

Ventilation
Supplying or removing air, by natural or mechanical means, to or from a space.

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