BS 9250:2007
$189.07
Code of practice for design of the airtightness of ceilings in pitched roofs
| Published By | Publication Date | Number of Pages |
| BSI | 2007 | 48 |
This 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 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 covering: 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, buildings.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 3 | Contents 1 Scope 1 2 Normative references 1 3 Terms and definitions 2 4 Design criteria 3 5 Materials, fittings and accessories 8 6 Design details and installation 11 Annexes Annex A (informative) Requirements for airtightness and control of condensation in the Building Regulations 38 Bibliography 40 List of figures Figure 1 – Defining the conditioned zone in a cold-roof building 5 Figure 2 – Defining the conditioned zone in a warm-roof building 6 Figure 3 – Joint in AVCL as a membrane with solid support, sealed using adhesive or double-sided tape 12 Figure 4 – Joint in AVCL as a membrane with solid support, sealed using adhesive or double-sided tape and secured with a compression batten 13 Figure 5 – Joint in AVCL as a membrane without solid support, sealed using adhesive tape (non-preferred solution) 14 Figure 6 – Continuity of AVCL ensured at stud partition 15 Figure 7 – Continuity of AVCL ensured at a purlin 16 Figure 8 – Joints in an air barrier formed by bevel-edged plasterboard, joined at a joist or rafter 17 Figure 9 – Joints in an air barrier formed by square-edged plasterboard, joined at a joist or rafter 18 Figure 10 – Ensuring an air-tight seal at the junction of a masonry cavity wall and ceiling using air-impermeable foil or lining paper 19 Figure 11 – Ensuring an air-tight seal at the top of a masonry cavity wall using plasterboard jointing tape (cold roof) 20 Figure 12 – Joints in an air barrier formed by a plasterboard-lined timber frame wall using plasterboard tape 21 Figure 13 – Joints in an air barrier formed by plasterboard lining a metal frame wall (cold roof) 22 Figure 14 – Joint in an air barrier formed by plasterboard lining an internally insulated wall (cold roof) 23 Figure 15 – Joint in an air barrier formed by plasterboard lining an externally insulated wall (cold roof) 24 Figure 16 – Join in a plastered masonry cavity wall using plasterboard jointing tape 25 Figure 17 – Join in a plastered internal block wall using plasterboard jointing tape 26 Figure 18 – Ensuring an air-tight seal at the top of a masonry cavity wall below a warm roof 27 Figure 19 – Warm roof construction with a small void above insulation 28 Figure 20 – Illustrative detail of a pipe penetration with collar 29 Figure 21 – Illustrative detail of a cable penetration with support and grommet 30 Figure 22 – Example of a pendant light fitting 31 |
| 4 | Figure 23 – Example of a flush light fitting 32 Figure 24 – Example of a recessed light fitting showing a sealed hood or box 33 Figure 25 – Illustrative detail of a drop-down loft hatch with seals 34 Figure 26 – Illustrative detail of a tubular rooflight 35 Figure 27 – Illustrative detail of a sealed ventilation duct in a ceiling 37 Figure 28 – Illustrative detail of a window in a warm roof 37 List of tables Table 1 – Whole building airtightness requirements by building type 4 Table 2 – Sealant types 9 Table 3 – Draught strips 9 |
| 5 | Foreword |
| 7 | 1 Scope 2 Normative references |
| 8 | 3 Terms and definitions 3.1 air barrier 3.2 air and vapour control layerAVCL 3.3 cold pitched roof 3.4 conditioned zone 3.5 vapour control layer VCL 3.6 warm pitched roof |
| 9 | 3.7 well-sealed ceiling 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, including 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 through cracks. f) The total leakage through all recessed light fittings should not exceed 0.06 m3/h·m2 of 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 loft 4 Design criteria 4.1 Airtightness of ceilings |
| 10 | 4.1.1 General 4.1.2 Airtightness requirements Table 1 Whole building airtightness requirements by building type |
| 11 | 4.1.3 Conditioned zones of the building and roof space 4.1.3.1 Cold roof Figure 1 Defining the conditioned zone in a cold-roof building |
| 12 | 4.1.3.2 Warm roof Figure 2 Defining the conditioned zone in a warm-roof building |
| 13 | 4.1.4 Halls and stairwells that connect directly to the ceiling at roof level (warm and cold roofs) 4.1.5 Bathrooms and kitchens that connect directly to the ceiling at roof level (warm and cold roofs) 4.2 Air barrier 4.3 Air and vapour control layers |
| 14 | 5 Materials, fittings and accessories 5.1 Air barriers/AVCLs 1) flexible plastic sheet (e.g. low density and high density polyethylene sheets are frequently used as air barriers); and/or 2) rigid material (e.g. plasterboard or plywood). 5.2 Sealants 5.2.1 Sealing tapes COMMENTARY ON 5.2.1 BS 7116 provides guidance for the selection of double-sided pressure sensitive self-adhesive tapes including self-adhesive foamed tapes. 5.2.2 Liquid sealants COMMENTARY ON 5.2.2 Sealants for building construction joints are classified in British Standards by performance requirements, b… |
| 15 | Table 2 Sealant types 5.3 Compressible foam (draught stripping) COMMENTARY ON 5.3 General information on choice of draught strips is given in Table 3. Table 3 Draught strips |
| 16 | 5.4 Loft hatches 5.5 Light fittings a) BS EN 60598-1 in conjunction with BS 4533-102.1/EN 60598-2-1 for pendant fittings and flush fittings; or b) BS EN 60598-1 in conjunction with BS EN 60598-2-2 for recessed fittings. |
| 17 | 5.6 Pipe boots/top hats COMMENTARY ON 5.8 Pipe boots or top hat seals around pipes are available in flexible single piece “pull over” or semi-rigid two part types. Such products may not be suitable for multi pipe penetrations. 5.7 Ventilators 5.8 Fire alarms 6 Design details and installation 6.1 General – Details in both cold and warm roofs 6.1.1 Installation of AVCLs |
| 18 | Figure 3 Joint in AVCL as a membrane with solid support, sealed using adhesive or double-sided tape |
| 19 | Figure 4 Joint in AVCL as a membrane with solid support, sealed using adhesive or double-sided tape and secured with a compression batten |
| 20 | Figure 5 Joint in AVCL as a membrane without solid support, sealed using adhesive tape (non-preferred solution) |
| 21 | Figure 6 Continuity of AVCL ensured at stud partition |
| 22 | Figure 7 Continuity of AVCL ensured at a purlin |
| 23 | 6.1.2 Joints in an air barrier formed by plasterboard Figure 8 Joints in an air barrier formed by bevel-edged plasterboard, joined at a joist or rafter |
| 24 | Figure 9 Joints in an air barrier formed by square-edged plasterboard, joined at a joist or rafter 6.2 Cold roofs 6.2.1 Ceiling-to-wall junctions 6.2.1.1 Plasterboard lined masonry cavity walls |
| 25 | Figure 10 Ensuring an air-tight seal at the junction of a masonry cavity wall and ceiling using air-impermeable foil or lining paper |
| 26 | Figure 11 Ensuring an air-tight seal at the top of a masonry cavity wall using plasterboard jointing tape (cold roof) |
| 27 | 6.2.1.2 Plasterboard lined timber frame walls Figure 12 Joints in an air barrier formed by a plasterboard-lined timber frame wall using plasterboard tape |
| 28 | 6.2.1.3 Plasterboard lined metal frame walls Figure 13 Joints in an air barrier formed by plasterboard lining a metal frame wall (cold roof) |
| 29 | 6.2.1.4 Plasterboard lined internally insulated solid walls Figure 14 Joint in an air barrier formed by plasterboard lining an internally insulated wall (cold roof) |
| 30 | 6.2.1.5 Plasterboard lined externally insulated walls Figure 15 Joint in an air barrier formed by plasterboard lining an externally insulated wall (cold roof) |
| 31 | 6.2.1.6 Plasterboard lined internal partitions 6.2.1.7 Plastered masonry cavity walls Figure 16 Join in a plastered masonry cavity wall using plasterboard jointing tape |
| 32 | 6.2.1.8 Plastered internal partitions Figure 17 Join in a plastered internal block wall using plasterboard jointing tape |
| 33 | 6.3 Warm roofs Figure 18 Ensuring an air-tight seal at the top of a masonry cavity wall below a warm roof |
| 34 | Figure 19 Warm roof construction with a small void above insulation |
| 35 | 6.4 Penetrations through ceilings 6.4.1 Pipes COMMENTARY ON 6.4.1 Where pipe seals or boot cannot be used it is important that any sealants or foams have some means of support during curing to ensure a well sealed junction. Figure 20 Illustrative detail of a pipe penetration with collar |
| 36 | 6.4.2 Cables Figure 21 Illustrative detail of a cable penetration with support and grommet 6.4.3 Light fittings |
| 37 | Figure 22 Example of a pendant light fitting |
| 38 | Figure 23 Example of a flush light fitting |
| 39 | Figure 24 Example of a recessed light fitting showing a sealed hood or box |
| 40 | 6.4.4 Loft hatches Figure 25 Illustrative detail of a drop-down loft hatch with seals |
| 41 | 6.4.5 Tubular rooflights Figure 26 Illustrative detail of a tubular rooflight |
| 42 | 6.4.6 Extraction outlets COMMENTARY ON 6.4.7 Extraction units, to which ducting is connected, remove unwanted water vapour from the building. It is impor… Figure 27 Illustrative detail of a sealed ventilation duct in a ceiling |
| 43 | 6.4.7 Roof windows Figure 28 Illustrative detail of a window in a warm roof |
| 44 | Annex A (informative) Requirements for airtightness and control of condensation in the Building Regulations A.1 Introduction A.2 Approved Document C – Site preparation and resistance to contaminants and moisture |
| 45 | A.3 Approved Document F – Ventilation A.4 Approved Document L – Conservation of fuel and power. |
| 46 | Bibliography [1] Airtightness in commercial and public buildings. B.C. Webb and R. Barton. Garston: BRE. 2002. [2] BRE IP 4/06. Airtightness of ceilings – Energy loss and condensation risk. Garston: BRE. March 2006. [3] BRE IP 5/06. Modelling condensation and air flow in pitched roofs. Garston: BRE. April 2006. [4] GREAT BRITAIN. Approved Document F – Ventilation, 2003. London: The Stationery Office. (http://www.planningportal.gov.uk) [5] GREAT BRITAIN. Building Regulations (Northern Ireland) 2000. (Amended 2005 and twice in 2006.) London: The Stationery Office. (http://www.planningportal.gov.uk) [6] SCOTLAND. Technical Handbooks 2007. Livingston: Scottish Building Standards Agency. (http://www.sbsa.gov.uk) [7] GREAT BRITAIN. Approved Document L2 – Air permeability requirements for buildings, 2006. London: The Stationery Office. (http://www.planningportal.gov.uk) [8] GREAT BRITAIN. Approved Document P – Electrical safety – Dwellings, 2006. London: The Stationery Office. (http://www.planningportal.gov.uk) [9] GREAT BRITAIN. Approved Document C – Site preparation and resistance to contaminants and moisture, 2006. London: The Stationery Office. (http://www.planningportal.gov.uk) [10] GREAT BRITAIN. Approved Document L1 – Conservation of fuel and power in dwellings, 2006. London: The Stationery Office. (http://www.planningportal.gov.uk) |
