1、BRITISH STANDARD BS 7456:1991 Incorporating Amendment No. 1 Code of practice for Stabilization and thermal insulation of cavity walls (with masonry or concrete inner and outer leaves) by filling with polyurethane (PUR) foam systemsBS7456:1991 This British Standard, having been prepared under the dir
2、ection of the Plastics and Rubber Standards Policy Committee, was published underthe authority of the Standards Board and comes intoeffect on 30 September 1991 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PRM/72 Draft for comment 88/43769 DC ISBN
3、0 580 19791 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics and Rubber Standards Policy Committee (PRM/-) to Technical Committee PRM/72, upon which the following bodies were represented: Association of Building Component Manuf
4、acturers Brick Development Association British Board of Agrment British Plastics Federation British Rigid Urethane Foam Manufacturers Association Calcium Silicate Brick Association Limited Cavity Foam Bureau Chief and Assistant Chief Fire Officers Association Department of the Environment (Building
5、Research Establishment) Department of the Environment (Construction Directorate) Engineering Equipment and Materials Users Association Flat Roofing Contractors Advisory Board Loss Prevention Council Ministry of Defence National Cavity Insulation Association National Federation of Roofing Contractors
6、 National House-building Council Phenolic Foam Manufacturers Association Polyethylene Foam Insulation Association Royal Institute of British Architects The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd. British
7、Urethane Foam Contractors Association (BUFCA) Department of the Environment Department of the Environment (Property Services Agency) RAPRA Technology Ltd. Amendments issued since publication Amd. No. Date Comments 8143 April 1994 Indicated by a sideline in the marginBS7456:1991 BSI 10-1999 i Content
8、s Page Committees responsible Inside front cover Foreword ii 0 Introduction 1 1 Scope 1 2 Definitions 1 3 Suitability of cavity walls 2 4 Polyurethane foam system 2 5 Thermal performance of installed polyurethane foam 2 6 Pre-installation preparation of the building 3 7 Filling process 3 8 Installat
9、ion of the polyurethane foam system 4 9 Post-installation activities 5 10 Declaration 6 11 Records 6 Appendix A Criteria of suitability of external cavity walls 8 Appendix B Fire performance of polyurethane foam when installed in a wall cavity 9 Appendix C Notes for designers 10 Appendix D Flue chec
10、ks for appliances of rated input not exceeding 60 kW 10 Appendix E Methods for determining cavity width 11 Figure 1 Staggered drilling pattern (representing maximum spacing) 4 Figure 2 Elevations of semi-detached property: unit area plan for injection 6 Figure 3 Overall pattern of filling for a nomi
11、nal 50 mm wide cavity 7 Figure 4 Measurement of cavity width 12 Figure 5 Estimation of cavity width 12 Publication(s) referred to Inside back coverBS7456:1991 ii BSI 10-1999 Foreword This British Standard has been prepared under the direction of the Plastics and Rubber Standards Policy Committee fro
12、m a draft prepared by the British Rigid Urethane Foam Manufacturers Association. Greater use is being made of insulation in construction as a consequence of changes in building regulations. The use of polyurethane (PUR) foam provides a means of providing thermal insulation in buildings of cavity wal
13、l construction having inner and outer masonry or concrete leaves, as well as providing a method of restoring the integrity of walls where the wall ties have become inoperative due to corrosion. A system of this type was first certified by the Agrment Board in 1975. This British Standard indicates cr
14、iteria for the selection of suitable buildings and defines the procedures and precautions to be followed to provide for the satisfactory injection of a PUR foam system into the cavity wall. The procedural advice and the controls needed on site have been fully detailed. BS 7457:1994 specifies rigid p
15、olyurethane foam systems which are suitable for use as described in this code of practice. It is recommended that installers have a quality management system complying with the requirements of Part 2 of BS 5750. A British Standard does not purport to include all the necessary provisions of a contrac
16、t. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 12, an inside back cover
17、 and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7456:1991 BSI 10-1999 1 0 Introduction A suitable polyurethane foam system may be injected into a masonry cavity w
18、all by injecting the liquid polyurethane system through properly spaced holes in the outer leaf. The polyurethane foam system expands in the cavity and sets to become a substantially closed-celled cross-linked rigid polyurethane foam which is strongly adhered to the inner and outer leaves, so that t
19、hese leaves become bonded together. Such a system comprises an isocyanate, a polyol (an isocyanate reactive resin usually containing two or more hydroxyl groups) and an expanding agent, which is a liquid at normal UK ambient temperatures and is usually incorporated as a liquid into the polyol compon
20、ent. Thus the operation consists on site of continuously mixing the two components correctly and inserting the resultant foam system into the cavity. The expansion results from the vapourization of the expanding agent due to the heat generated by reaction of the polyol and isocyanate. Because the st
21、rength of the rigid polyurethane foam is significant the system has been widely used for the restoration of the integrity of cavity walls in which the wall ties have become ineffective due to corrosion. The installed rigid polyurethane foam thus confers two benefits namely insulation and interleaf b
22、onding. Provided that the precautions referred to in this code of practice are followed no hazard should arise during or after installation. It should be stressed that, while polyurethane foam is a satisfactory replacement for normal metal wall ties, it does not prevent corrosion of existing ties in
23、 a wall nor halt the deterioration caused by such corrosion. All installations in walls to deal with corroding wall ties have to be accompanied by a suitable treatment of the existing ties such as removal, isolation (see A.9). 1 Scope This British Standard gives recommendations for the installation
24、of rigid polyurethane (PUR) foam systems complying with BS 7457:1994, which are dispensed on site, to fill cavities of maximum width150 mm of suitably constructed external walls of maximum continuous cavity height 12 m which have masonry or concrete inner and outer leaves, thereby providing addition
25、al thermal insulation to such walls and simultaneously, especially in the case of walls with damaged wall ties, improving their structural integrity. It defines what are suitably constructed external walls and indicates essential procedures and precautions necessary to optimise the filling process.
26、Walls built of random rubble are not covered by this code. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the following definitions apply. 2.1 cavity an air space between two leaves of an ex
27、ternal wall 2.2 polyurethane foam the cellular polymer resulting from the reaction of the two components of the foam system, i.e. the isocyanate and polyol components 2.3 polyurethane foam system a mixture of polyol component and isocyanate component which is to be injected into the cavity wall 2.4
28、indicator stick a rod, typically 5 mm in diameter and 250 mm long, inserted through an injection or sight hole in the leaf of a wall into the cavity to monitor the movement of the polyurethane foam in the wall cavity at that point during the filling process 2.5 installation contractor a company or o
29、rganization that undertakes the injecting of a suitable polyurethane foam system into wall cavities in order to restore the structural integrity and enhance thermal insulation 2.6 sight hole an additional hole drilled through either leaf of a wall into the cavity, used only to check that the polyure
30、thane foam system has reached that point in the cavity 2.7 unit area plan a method of dividing up the exterior walls of the building to show the sequence of foaming through the injection holesBS7456:1991 2 BSI 10-1999 2.8 cavity closer a building feature closing a cavity around an opening in the wal
31、l NOTEExamples are a sill or a lintel. 2.9 stop-end a vertical cavity closer, such as a reveal block, which limits the horizontal travel of a polyurethane foam system during injection 2.10 cream time the time taken after the polyurethane foam system(2.3) has been mixed for visible expansion to comme
32、nce 2.11 end of rise time the time taken after the polyurethane foam system(2.3) has been mixed for the foam expansion to be visibly completed 2.12 tack free time the time taken after the polyurethane foam system(2.3) has been mixed for the surface of the expanded polyurethane foam not to adhere to
33、the test stick 2.13 cavity brush a device introduced into a wall cavity to provide a barrier to the movement of the polyurethane foam 3 Suitability of cavity walls 3.1 General It is essential that only if the installation contractor(2.5) considers the building to be suitable or capable of being made
34、 suitable, should installation be carried out (see 3.2). Rectification of any defects should be carried out beforehand or form part of the contract. 3.2 Determination of suitability All the aspects in BS 8208-1 should be taken into account when assessing the general suitability of cavity walls for i
35、nsulation. In particular in this standard points of significance regarding suitability have been detailed in Appendix A. It is also essential that a survey document be prepared to record the results of the survey to be carried out which should include the following: a) a study of all relevant drawin
36、gs, if available, concerning the building structure; b) identification of any gaps which will allow the polyurethane foam system to escape from the cavity (e.g. gaps around windows, skirting boards and at the top of cavities); c) an inspection of the cavities using a borescope to assess the followin
37、g: 1) the general condition of the cavity (seeA.2.5); 2) the presence of any efflorescence; 3) the condition of damp-proof courses; 4) the failure of (and likely mode of failure of) any wall ties; 5) the necessity to remove wall ties (see A.9); 6) the positions of flues or other services present (e.
38、g. electrical cables) (see A.7); 7) whether a vapour barrier has been installed on the inner face of the outer leaf, since if such a vapour barrier is present foam should not be installed. In the case of a new construction allowance should be made for this in the design of the building; 8) the need
39、to remove debris (see clause 6); 9) whether the cavities have been closed at the top (see A.3); 10) the presence and location of any flues which need protection by applying non-combustible thermal insulation to prevent the polyurethane foam from coming into contact with the flue material (seeA.2.6 a
40、nd Appendix B). 4 Polyurethane foam system It is essential that the polyurethane foam system used in the filling process complies with BS7457:1994. 5 Thermal performance of installed polyurethane foam The thermal conductivity value used for design purposes should take into account the limited diffus
41、ion of gases that can take place in the foam with time. Generally this will be higher than or equal to the 30 day value. Additional information on this recommendation is contained in Annex A of BS7457:1994.BS7456:1991 BSI 10-1999 3 6 Pre-installation preparation of the building Carry out any rectifi
42、cation identified as necessary under 3.2. It is essential that cavities should be cleared by opening up at intervals along the damp course and above lintels and reveals. Debris should be removed, if necessary, from the cavity to a depth of 150 mm below the damp proof course. Any water should also be
43、 removed. It is also necessary to ensure that the following checks are carried out. a) All combustion appliances with flues against, through or adjacent to a cavity wall that is to be filled are to be operated to observe their performance prior to injection of the polyurethane foam system. b) The po
44、sition and purpose of all flues and vents are to be noted so that a proper drilling and injection pattern can be planned for the building. c) Holes in the cavity wall, especially in the inner leaf, are effectively sealed (for example with mortar) to limit the entry of the foam system or any vapours
45、into the occupiable parts of the building. d) Vents are sleeved using a non-combustible material to maintain facilities for air flow to (e.g. sub floor areas, larders, roof spaces, toilets, bathrooms) permanently ventilated areas. e) Means are provided at the junction of party walls to prevent spill
46、age of polyurethane foam system into the wall cavity of the adjoining property, e.g. by the installation of cavity brushes(2.13). f) If the window or door frames cross the cavity, that they are braced prior to installation of the polyurethane foam system to prevent distortion occurring. g) Cavities
47、are closed at the top with a non-combustible material if possible. Provided that all the checks detailed in a) to g) have been made and appropriate rectification effected where necessary, there will be no vapour hazard either during or after installation. Tests have shown that the occupational expos
48、ure limits (OEL) 1)for vapours of MDI 2)have never yet been exceeded within a building or outside a building during or after installation. 7 Filling process 7.1 General Rigid polyurethane foam is formed by reacting as two components an isocyanate with a polyhydroxyl compound containing an expanding
49、agent, catalysts and other additives. The liquid components are mixed in a hand gun and injected into the cavity wall through a series of holes, drilled in a predetermined pattern in the wall. The liquid mixture reacts in the cavity producing a cellular polymer which hardens into a rigid foam bonding strongly to inner and outer leaves of the cavity wall. NOTEBecause polyurethane foam can be difficult to remove when hardened any spillage should be cleaned up as soon as possible. 7.2 Storage Both the polyol component and the isocyanate component will have finite sh
