1、BS 9250:2007Code of practice for design of the airtightness of ceilings in pitched roofsICS 91.060.20; 91.120.99NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when
2、 the document was last issued. BSI 2007ISBN 978 0 580 50809 7The following BSI references relate to the work on this standard:Committee reference B/542/1Draft for comment 06/3017888 DCPublication historyFirst published May 2007Amendments issued since publicationAmd. no. Date Text affectedBS 9250:200
3、7 BSI 2007 iBS 9250:2007ContentsForeword iii1 Scope 12 Normative references 13 Terms and definitions 24 Design criteria 35 Materials, fittings and accessories 86 Design details and installation 11AnnexesAnnex A (informative) Requirements for airtightness and control of condensation in the Building R
4、egulations 38Bibliography 40List of figuresFigure 1 Defining the conditioned zone in a cold-roof building 5Figure 2 Defining the conditioned zone in a warm-roof building 6Figure 3 Joint in AVCL as a membrane with solid support, sealed using adhesive or double-sided tape 12Figure 4 Joint in AVCL as a
5、 membrane with solid support, sealed using adhesive or double-sided tape and secured with a compression batten 13Figure 5 Joint in AVCL as a membrane without solid support, sealed using adhesive tape (non-preferred solution) 14Figure 6 Continuity of AVCL ensured at stud partition 15Figure 7 Continui
6、ty of AVCL ensured at a purlin 16Figure 8 Joints in an air barrier formed by bevel-edged plasterboard, joined at a joist or rafter 17Figure 9 Joints in an air barrier formed by square-edged plasterboard, joined at a joist or rafter 18Figure 10 Ensuring an air-tight seal at the junction of a masonry
7、cavity wall and ceiling using air-impermeable foil or lining paper 19Figure 11 Ensuring an air-tight seal at the top of a masonry cavity wall using plasterboard jointing tape (cold roof) 20Figure 12 Joints in an air barrier formed by a plasterboard-lined timber frame wall using plasterboard tape 21F
8、igure 13 Joints in an air barrier formed by plasterboard lining a metal frame wall (cold roof) 22Figure 14 Joint in an air barrier formed by plasterboard lining an internally insulated wall (cold roof) 23Figure 15 Joint in an air barrier formed by plasterboard lining an externally insulated wall (co
9、ld roof) 24Figure 16 Join in a plastered masonry cavity wall using plasterboard jointing tape 25Figure 17 Join in a plastered internal block wall using plasterboard jointing tape 26Figure 18 Ensuring an air-tight seal at the top of a masonry cavity wall below a warm roof 27Figure 19 Warm roof constr
10、uction with a small void above insulation 28Figure 20 Illustrative detail of a pipe penetration with collar 29Figure 21 Illustrative detail of a cable penetration with support and grommet 30Figure 22 Example of a pendant light fitting 31BS 9250:2007ii BSI 2007Figure 23 Example of a flush light fitti
11、ng 32Figure 24 Example of a recessed light fitting showing a sealed hood or box 33Figure 25 Illustrative detail of a drop-down loft hatch with seals 34Figure 26 Illustrative detail of a tubular rooflight 35Figure 27 Illustrative detail of a sealed ventilation duct in a ceiling 36Figure 28 Illustrati
12、ve detail of a window in a warm roof 37List of tablesTable 1 Whole building airtightness requirements by building type 4Table 2 Sealant types 9Table 3 Draught strips 9Summary of pagesThis document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 40, an inside back cover and
13、a back cover. BSI 2007 iiiBS 9250:2007ForewordPublishing informationThis British Standard was published by BSI and comes into effect on 31 May 2007. It was prepared by Subcommittee B/542/1, Slating and tiling, under the authority of Technical Committee B/542, Roofing and cladding products for discon
14、tinuous laying. A list of organizations represented on this committee can be obtained on request to its secretary.Information about this documentIn the UK some 70% to 80% of houses and some larger buildings such as schools and hospitals have cold pitched roofs, with insulation on the horizontal ceil
15、ing and an accessible, cold loft space above. Gaps in the ceiling, such as around loft hatches and service pipes, allow air to flow from the living space to the loft. Some of the heat and moisture generated in the living space passes through the gaps into the loft contributing to the energy loss fro
16、m the building and creating a risk of condensation in the loft space.Buildings with warm pitched roofs, where the insulation is at rafter level, use the loft as living space. If the walls and ceilings of the “room in the roof” have gaps through which air can flow, this will provide a route for energ
17、y loss and an increased risk of condensation.BS 5250, the code of practice for the control of condensation in buildings, recommends that air leakage through ceilings should be minimized and provides criteria for a “well sealed ceiling”. This standard provides practical guidance on methods for fulfil
18、ling the “well sealed ceiling” criteria. Use of this documentAs a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading.A
19、lthough this standard is intended for the design of domestic buildings, it also has more general relevance to other buildings.Any user claiming compliance with this British Standard is expected to be able to justify any course of action that deviates from its recommendations.Presentational conventio
20、nsThe provisions in this standard are presented in roman (i.e. upright) type. Its recommendations are expressed in sentences in which the principal auxiliary verb is “should”.Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a norma
21、tive element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.iv BSI 2007 This page deliberat
22、ely left blankBS 9250:2007 BSI 2007 1BS 9250:20071 ScopeThis standard provides guidance on methods that can be used to meet the “well sealed ceiling” requirements defined in BS 5250 for cold and warm pitched roofs.This standard provides architects, house builders, and building control officers with
23、robust design details for the construction of more airtight ceilings and for the control of air movement into pitched roofs.It provides guidance for dwellings and buildings of domestic type construction on the selection of materials, design principles, construction methods and design details coverin
24、g: the junction of walls and ceilings; junctions of ceiling materials; penetration through ceilings (e.g. pipes, outlets, cables, light fittings, loft hatches, tubular rooflights and roof windows).It includes cold and warm roof applications and will apply to new, and the refurbishment of existing, b
25、uildings.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.BS 4255-1, Rubber u
26、sed in preformed gaskets for weather exclusion from buildings Part 1: Specification for non-cellular gasketsBS 4533-102.1/EN 60598-2-1, Luminaires Part 102: Particular requirements Section 102.1 Specification for fixed general purpose luminairesBS 5250, Code of practice for control of condensation i
27、n buildings BS 6093, Code of practice for design of joints and jointing in building constructionBS 6213, Selection of construction sealants GuideBS 7116, Specification for double sided pressure sensitive adhesive tapesBS 7412, Plastics windows made from unplasticized polyvinyl chloride (PVC-U) extru
28、ded hollow profiles SpecificationBS 8000-16, Workmanship on building sites Part 16: Code of practice for sealing joints in buildings using sealantsBS EN 60598-2-2/IEC 598-2-2, Luminaires Part 2: Particular requirements Section 2: Recessed luminairesBS EN 13141-1, Ventilation for buildings Performanc
29、e testing of components/products for residential ventilation Part 1: Externally and internally mounted air transfer devicesBS EN 13963, Jointing materials for gypsum plasterboards Definitions, requirements and test methodsBS 9250:20072 BSI 20073 Terms and definitionsFor the purposes of this standard
30、, the following terms and definitions apply.3.1 air barrierbarrier comprising materials and/or components which are air impervious or virtually so, separating conditioned spaces (heated/cooled) from unconditioned spaces (unheated/cooled)NOTE An air barrier will not necessarily be vapour impervious.F
31、rom Airtightness in Commercial Public Buildings 13.2 air and vapour control layerAVCLsingle layer (often a membrane) controlling both air and vapour movement, thereby fulfilling the role of both an air barrier and a vapour control layerNOTE 1 The term “air and vapour control layer” has been adopted
32、throughout this standard recognizing that a well designed and installed vapour control layer also controls air movement.NOTE 2 The performance of an air and vapour control layer is dependent upon the material, workmanship and buildability, all of which need to be assessed by the designer.3.3 cold pi
33、tched roofpitched roof that has insulation on the horizontal ceiling and an unheated loft above that ceiling3.4 conditioned zoneoccupied zone in a building requiring heating or cooling and bounded by an airtightness layer or an air and vapour control layer to separate it from unconditioned zonesBase
34、d on Airtightness in Commercial Public Buildings 13.5 vapour control layerVCLmaterial of construction which substantially reduces the water vapour transfer through any building element in which it is incorporated or applied by limiting vapour diffusion (see BS 5250)NOTE 1 A well installed VCL will a
35、lso control air movement and in this standard is referred to as an “air and vapour control layer”.NOTE 2 The term “vapour control layer” is preferred to the terms “vapour check” and “vapour barrier” which usually refer to the materials alone. The performance of a vapour control layer is dependent up
36、on the material, workmanship and buildability, all of which need to be assessed by the designer.3.6 warm pitched roofpitched roof that has insulation at rafter level, providing a loft that can be used as a living space BSI 2007 3BS 9250:20073.7 well-sealed ceilingceiling that satisfies the following
37、 criteria:a) The design avoids constructional gaps, especially at the wall/ceiling junction and holes in the ceiling.b) No access door or hatch should be located in rooms where large amounts of moisture are produced, including kitchens or bathrooms.c) The air leakage rate through an access hatch, in
38、cluding its frame, when tested to BS EN 13141-1:2004 4.3 is less than 1 m3/h at a pressure difference of 2 Pa. d) Penetrations, such as those for services and rooflights, are permanently sealed with suitable proprietary products.e) The ceiling is sealed to the external walls to limit any leakage thr
39、ough cracks.f) The total leakage through all recessed light fittings should not exceed 0.06 m3/hm2of ceiling at 2 Pa pressure difference across the ceiling. g) The head of any cavity in any wall or partition should be sealed to prevent transfer of warm moist air into the loftBased on BS 52504 Design
40、 criteria4.1 Airtightness of ceilingsCOMMENTARY ON 4.1 Measurements in a range of houses have shown that, typically, 20% of the air entering the occupied rooms will leave via a cold loft, taking with it moisture and heat. The proportion entering a warm roof will be smaller, but can have a relatively
41、 greater risk of condensation because of the smaller volumes within the roof.Tests have shown that with 200 mm of mineral wool (an R-value of 4.50 m2W/K) on the floor of a cold loft and a typical unmodified ceiling, about half the heat transport into the roof takes place by air movement, with the ot
42、her half passing through the ceiling and insulation by conduction. Air movement was even more important in the case of moisture transport, carrying over 75% of the water vapour entering a cold loft from the rooms below, with the rest going by diffusion through the ceiling materials.There are therefo
43、re two benefits from ensuring that air movement from the occupied rooms in a house into the roof is minimized as far as possible:a) The heat loss and total energy demand of the house will be reduced. The change from a typical unsealed ceiling to a well sealed ceiling (see 3.5), which reduces the air
44、 transport into the roof by 70%, will save about 8% to 10% of the energy consumed in a typical house.b) The flow of moisture into the roof will be reduced very significantly, in most cases eliminating the risk of damaging condensation. A well sealed ceiling is a precondition of most third-party cert
45、ification of low vapour resistance underlays used in unventilated cold pitched roofs. However, where moisture loads in the building are likely to be high, an AVCL will be needed. BS 9250:20074 BSI 2007A BRE Information Paper, IP4/06, The airtightness of ceilings energy loss and condensation risk 2 p
46、rovides a more detailed explanation of the building physics relating to the condensation risk and energy losses in cold pitched roofs.The procedure for assessing the risks of condensation within structures that was specified in BS 5250:2002, makes use of a calculation procedure in BS EN ISO 13788:20
47、01. Because this procedure allows for only conduction and diffusion and specifically excludes structures with air flows through cracks and cavities, it cannot be used for assessing cold pitched roofs. This situation is noted in Amendment 1 of BS 5250:2002 and a second BRE Information Paper, IP 5/06
48、Modelling condensation and airflow in pitched roofs 3, has been published to give recommendations for the necessary assessment procedure.Reducing the ventilation rate in the conditioned zone can potentially cause problems of condensation and mould within the occupied rooms. The provisions of Approve
49、d Document F 4 in England and Wales (Building Regulations (Northern Ireland) 5 Part K or Building (Scotland) Regulations 2004 Technical Handbook 6 Section 3) and its associated guidance documents always have to be followed to ensure that the moisture produced by normal household activities is removed at source.4.1.1 GeneralAt the design stage the following should be considered: the conditioned zones of the building and
