Electronic Copy Design Data 7 General 7.1 Thermo-Foil ES, Thermo-Foil, Eco-Brite and Tape (Radiant Heat Barrier System) are effective in reducing the U value (thermal transmittance) in new or existing: solid or cavity masonry walls and timber-framed walls and ceilings ground supported, suspended, exposed and semi-exposed concrete and timber floors. Suspended ground floors must include suitable ventilation or a damp-proof membrane. The products also act as a vapour control layer in dwellings and buildings of similar occupancy, type and condition. 7.2 When the products are used as the vapour control layer it is essential that proper care and attention is given to maintaining its integrity and continuity. Further information is given in BRE Report No 262 : Thermal insulation : avoiding risks. 7.3 Where constructions need to comply with NHBC Standards or Zurich Building Guarantees Technical Standards, specifiers should observe the requirements of these documents. 7.4 The use of the products does not in itself promote infestation. The creation of voids within the structure, ie gaps between the wall lining and the sheet, may provide habitation for insects or vermin in areas already infested and such infestation may be difficult to eradicate. There is no food value in the materials used. Walls 7.5 New buildings should be designed and constructed in accordance with the relevant recommendations and codes of practice, namely BS 5268-2 : 1996 and/or BS 5628-3 : 2001. The walls must be in a good state of repair with no evidence of rain penetration, damp or frost damage. Roof tile underlay 7.6 When used as a roof tile underlay and/or heat reflecting barrier, the products must be installed in accordance with the Certificate holder’s instructions. 7.7 The products provide a satisfactory underlay in tiled and slated, ventilated pitched roofs constructed in accordance with BS 5534-1 : 1997. 7.8 The aluminium facings of the products, in conjunction with an air space, will contribute to increasing the thermal resistance of that air space. 7.9 Due to the reflective finish on the products, distortion of television reception may occur when using an aerial in the roof space. External aerials will not be affected. 4 8 Thermal insulation 8.1 For the purpose of U value calculations to determine if the requirements of the national Building (or other statutory) Regulations are met, it has been established by test that the product will provide additional thermal resistance, which can be incorporated into the calculations (see Table 2). For the purpose of establishing thermal resistance values, an emissivity of 0.05 (reflectivity of 0.95) may be used. Table 2 Thermal resistance values Direction of heat flow Thermal resistance values(1) (m2KW–1) of Thermo-Foil ES, Thermo-Foil, Eco-Brite and Tape with a minimum air space on one side 25 mm 0.45 0.51 0.67 0.80 Element of structure Ceiling Pitched roof (45°) Wall Floor upward upward horizontal downward (1) Thermal resistances were calculated to BS EN ISO 6946 : 1997 for a mean temperature of 10°C. 8.2 The requirement for limiting the heat loss through the building fabric will be satisfied if the U values of the building elements, including thermal bridging, do not exceed the maximum values in the relevant Elemental Method given in the national Building Regulations thus: England and Wales Approved Documents L1 or L2, Table 1 Scotland Technical Standards, Table 1 to J3.2 or Table to J8.3 Northern Ireland Technical Booklet F, Table 1.2 or 1.4. 8.3 Alternative approaches are also described in these documents, which allow for some flexibility in design of U values for individual constructional elements. 8.4 The ultimate thermal performance of the product will depend on the construction of the wall or ceiling against which it is installed. The dynamic performance of a structure can be determined by the admittance procedure given in CIBSE Guide A : 1999 Environmental Design. 8.5 The dynamic thermal performance of a building can be expressed as a ratio called the response factor (Equation 5.13 of CIBSE Guide A). Factors 4 are achieved for thermally-lightweight buildings and factors >4 for heavyweight buildings. The use of any form of insulation will affect this factor and it should be considered when designing heating systems for new buildings. Modifications to existing heating systems may also have to be considered in buildings upgraded by the application of the product. Methods of sizing heating plant are given in Section 5 of the CIBSE Guide A. previous page next page