1、 BSI BS*7021 O1 1b24bb9 0403154 430 BS 7021 : 1989 UDC 678.06 : 69.024.1 : 678.026.34 :678.664 : 691 : 001.4 : 614.8 : 620 .1 : 006.76(083.75) 1 0 British standards Instihition. No part of this publiestion may be pbmcopd . o( otherwise reproduced without the prior permission in Writing of BSI Britis
2、h Standard Code of practice for Thermal insulation of roofs externally by means of sprayed rigid polyurethane (PUR) or polyisocyanurate (PI R) foam Isolation thermique extrieure des toitures par plaques rigides de mousse de polyurthane (PUR) ou de polyisocyanurate (Pi RI- Code de bonne pratique Leit
3、faden zur Auenwrmedrnrnung von Dchern mit PUR-oder PIR-Hartschaurn British Standards Institution 4 6; -. BSI BS+702L O1 lb2Ybbq 0403155 377 BS 7021 : 1989 Foreword This British Standard has been prepared under the direction of the Plastics Standards Committee from a draft submitted by the British Ur
4、ethane Foam Contractors Association. It gives recommendations for the thermal insulation of roofs, externally, by the application of sprayed rigid polyurethane (PUR) or polyisocyanurate (PIR) foam, including criteria for determining the suitability of roofs for spraying. In addition guidance is incl
5、uded on the following: (a) determining the suitability of roof surfaces for direct spraying; (b) the preparation of roof surfaces prior to spraying; (c) the selection and application of primers and vapour barriers; (d) the selection and application of the external protective membrane applied after s
6、praying; (e) the fire performance of the modified roof as well as guidance on the health and safety aspects associated with the work. Attention is drawn to BS 5241 : Part 1 which specifies suitable PUR and PIR foam systems for use as recomm- ended in this code of practice and is published simultaneo
7、usly. Attention is also drawn to the fact that polyurethane or polyisocyanurate rigid foams are organic and hence combustible. It is important therefore that reference be made to clauses 10 and 11 dealing with health and safety aspects and fire performance respectively. Finally attention is drawn to
8、 the precautions indicated in 5.2.2 for work on asbestos sheet roofs. Compliance with a British Standard does not of itself confer immunity from legal obligations. BS 7021 : 1989 Contents Page Foreword Committees responsible Inside front cover Back cover Code of practice O Introduction 2 Definition
9、3 Composition and designation 4 Thermal performance of installed foam 5 Insulation of existing roofs 6 Insulation of new roofs 7 Primers and vapour check coatings 8 Foam application procedure 9 Protective mem branes 1 scope 10 Health and safety aspects 11 Fire performance Appendices A Method for det
10、ermining the on-site adhesive strength of sprayed rigid PUR or PIR foam B Method for the on-site determination of overall foam density Figures 1 2 3 4 5 Typical self-adhesive force applicator Characteristic sprayed foam surface texture: smooth Characteristic sprayed foam surface texture: orange peel
11、 Characteristic sprayed foam surface texture: pop corn Characteristic sprayed foam surface texture: tree bark 2 2 2 2 2 2 4 5 5 7 8 9 13 14 9 10 11 12 13 1 BSI BS17021 01 II624669 0403157 L4T = BS 7021 : 1989 Code of practice O Introduction Rigid PUR or PIR foam is applied by spraying on to the exte
12、rior surfaces of the roofs of buildings to reduce heat losses. After curing automatically, the foam is in the form of an auto-adhesive continuous covering of insulation of the correct thickness to confer on the roof a predetermined thermal transmittance value. The foam is applied to new and existing
13、 roofs of any configuration, although it is presently confined, in the UK, to the roofs of industrial, commercial and institutional buildings rather than domestic dwellings. Sprayed foam can be applied to almost all roofing materials although their surface preparation procedures often differ. This m
14、ethod of applying thermal insulation is particularly suitable for existing roofs. Providing the existing roof is sound the foam can be sprayed on to the old surface. If sections have deteriorated it is necessary to replace them before applying sprayed foam. The foam is always protected by a protecti
15、ve membrane which is sprayed on to the foam as soon as possible after the latter has cured. The function of the membrane is to protect the foam from solar radiation and from the ingress of water. These membranes are auto-adhesive continuous films which follow exactly the surface of the foam, They ar
16、e usually in the form of durable elastomeric materials which have a high weather resistance. Both the foam and the membrane are applied by means of purpose-built spraying machines. The foam components are delivered to the site as liquids. The foam components (usually two) are pumped under pressure b
17、y the machine in metered amounts and are intimately mixed in the spray gun when spraying. It is essential that spraying is carried out by trained operators. The reaction between the mixed liquids causes expansion of the inherent expanding agent to form the final foam. The membrane ingredients are us
18、ually premixed on site immediately prior to its application. 1 Scope This British Standard code of practice gives recommend- ations for the thermal insulation of roofs externally by spraying with rigid polyurethane (PUR) or polyisocyanurate (PIR) foam, and their subsequent protection by means of a p
19、rotective membrane applied in liquid form. NOTE. The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definition For the purposes of this British Standard the following definition applies. 2.1 flat roof. A roof having an angle to the horizontal of less t
20、han 10 and otherwise complying with the requirements of BS 6229. 3 Composition and designation 3.1 General It is essential that the thermally insulating sprayed polyurethane (PUR) or polyisocyanurate (PI RI foam should comply with BS 5241 : Part 1. 3.2 Designation It is essential that designers spec
21、ify, in accordance with BS 5241 : Part 1, the correct type of foam for their particular application.?lpe 2 and type 4foams with their higher compressive strengths are for general use on roofs and flat roofs, whereas type 1 and type 3should be considered only for applications where the higher compres
22、sive strength characteristics are not needed, e.g. roof surfaces with a slope greater or equal to 45. 4 Thermal performance of installed foam The thermal conductivily value used for design p (2) edges of adjacent deck units should be fully supported or attached to prevent differential movement under
23、 load. 6.2 Surface preparation 6.2.1 General. Sprayed foam can be applied to any suitably prepared roof deck material, including timber, woodwool, concrete, profiled metal and corrugated sheeting or cement/ fibre composites. Preparation procedures pertinent to particular materials are given in 6.2.2
24、 to 6.2.5 inclusive. 6.2.2 Concrete and screeded roofs. Concrete and cement screeds can become waterlogged if not adequately protected. Vents are rarely effective in removing this water and provision should be made for drainage downwards. This can be achieved by the installation of appropriately spa
25、ced temporary holes in the structural concrete roof. Lightweight aggregate and aerated concrete screeds are best avoided, since they have a tendency to hold water. It is essential that a waterproof membrane should be applied before the application of the sprayed foam to provide weather protection, t
26、o protect the foam from residual moisture in the substrate and to act as a vapour check to reduce interstitial condensation. 6.2.3 Timber decking and woodwool slabs. Timber decking and woodwool slabs should be adequately fixed and protected from moisture by the application of built up roofing. Spray
27、ed foamshould not be applied directly to timber decking or woodwool slabs. Unfaced boards and tongued and grooved timber should be protected by a two layer bituminous membrane applied on site. The first layer should be partially attached either by nailing or by the use of a perforated membrane of ty
28、pe 3G in accordance with BS 747. The second layer should then be fully bedded in hot bitumen. Timber decking should be designed to the requirements of NHBC practice note No. 13. Special attention should be paid to edge detailing to ensure adequate support, continuity of the vapour check and allowanc
29、e for any differential movement. 6.2.4 Troughed metal decking and sheeting 6.2.4.1 Decking and sheeting flat roofs with a pitch of less than 4O. When the pitch of the flat roof is less than 4“. water cannot drain fully from the troughs of the decking and therefore a flat rigid board should be attach
30、ed to the top of the decking to receive the sprayed foam. Such boards should be restrained against wind uplift and protected against the ingress of moisture during construction. Various types of rigid boards are suitable, including the following materials: (a) wood chipboard of type II or I i/i I I
31、in accordance with BS 5669; (b) exterior grade plywood in accordance with BS 1088 (c) insulating board in accordance with BS 1142 : Part 3. Various grades of rigid insulation board may also be suitable but compressible material, e.g. mineral fibre, should not be used. Boards should be attached by bo
32、nding with a suitable adhesive such as hot bitumen or by mechanical means. Suitable screw fixings should be applied at a rate of not less than five per square metre. More fixings will be required in areas of high wind uplift and into aluminium decking. Built-up roofing should be applied to act as a
33、weather protection and vapour check. 6.2.4.2 Decking and sheeting roofs with a pitch greater than or equal to 4O. Sprayed foam should be applied directly to the troughed metal sheeting. Such roofs should be constructed using protected steel or aluminium sheets and fixed in accordance with CP 143: Pa
34、rts 1 and 10. The roofs should be constructed with falls into separate eaves or valley gutters. The application of sprayed foam into gutters is not recommended and the use of an insulated metal or glass reinforced plastics gutter system is preferable. The sheets should be fixed using self tapping sc
35、rews with sealing washers set into the sheet troughs. End and side laps should be sealed using a mastic strip to prevent the passage of moisture. Cappings and other flashings should be rigid and adequately fixed to prevent excessive movement that could rupture the foam. 6.25 Corrugatedcement fibre s
36、heets. It is essential that corrugated cement fibre sheets are fixed in accordance with the manufacturers instructions since the application of sprayed foam does not strengthen the sheeting. CAUTION. It is essential that fragile roof notices are erected at all access points. 4 BSI BS*702L OL m Lb24b
37、b 04031ibO 734 m Where a vapour check is required all sheeting laps should be sealed and the sheeting treated with an appropriate two coat proprietary sealing compound (see 7.2). Separate insulated gutters should be provided as with metal roofs. Cement fibre sheeting should be generally fixed using
38、projecting hook bolts through the crown. Such projections should be kept to the minimum. 7 Primers and vapour check coatings 7.1 Primers Primers are occasionally required to be applied prior to spraying with foam. They should be applied strictly in accordance with the suppliers instructions and allo
39、wed to dry thoroughly for the period specified by the supplier before applying the foam. Some primer coatings are specified to protect the substrate, e.g. mild or stainless steel. NOTE. BS 5493 gives information on the wide variety of coating systems available for use on steel. Additional informatio
40、n ir available from coating manufacturers. 7.2 Vapour check coatings Where condensation is occurring the application of sprayed foam will greatly reduce or eliminate the problem altogether by keeping the temperature of the existing roof structure above the dew point for a given relative humidity lev
41、el existing inside the building. Such situations should be carefully analysed to ensure that there will be no excessive and progressive build-up of interstitial condensation in the foam. The foam has a low but finite water vapour transmission rate, so if there is a risk of interstitial condensation
42、this can be reduced by the application of a vapour check coating on the warm side of the foam. For new roofs the attention of the roof designer is drawn to the appropriate guidance contained in BS 6229 when determining if a vapour check coating should be installed. On existing roofs the existing wat
43、erproofing will often provide sufficient resistance to the passage of water vapour. Where greater resistance is required, a continuous elastomeric coating of low permeability should be used. 7.3 Application procedure 7.3.1 Surface preparation. It is essential that the surface to receive the coating
44、should be clean and dry. Surface preparation should be carried out as detailed in 6.2. 7.3.2 Application of primer or vapour check coatings Coatings may be applied by brush roller or spraying equipment. The spraying equipment should be in good working order. Compressed air sources should have moistu
45、re traps from which water should be bled frequently. Before the application of a non-aqueous system begins, all hoses and guns should be flushed out with solvent. It is essential that all flames and sparks should be avoided. Welding and smoking in the application area should be prohibited, and spray
46、 guns earthed. Coatings should not be applied in cold, damp conditions where there is likely to be surface moisture. The coating airless BS 7021 : 1989 suppliers instructions should be followed at all times. Vapour check coatings should be applied in at least two layers using the technique of cross-
47、hatching to ensure complete coverage and avoiding the formation of pin-holes. 7.3.3 Quality control. Before the application of foam the substrate should be visually examined to check that the roof is covered by the applied coating. Regular samples should be taken to check for adhesion and coating th
48、ickness. Any areas not complying with the suppliers specification should be re-coated. 8 Foam application procedure 8.1 Dispensing machine The foam systems should be sprayed through standard purpose-built machines, which have at least the following facilities: (a) positive displacement metering pump
49、s which accurately pump the components as separate streams to the mixing spray gun at the correct ratio, e.g. double acting piston pumps joined to a comvon yoke with cross-sectional area ratios equivalent to the volume mixing ratio of the chemical system in use; (b) a mixing spray gun which intimately mixes and dispenses the mixed components in the form of a spray; (c) temperature controlled, in-line, heat exchangers and hoses; (d) pressure and temperature gauges for each component hose. 8.2 Liquid foam components It is essential that all containers of liquid components sho
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