DESIGN PROCESS
Rain noise Rain noise should be considered at design stage where quiet conditions are essential or where interference with speech communication is undesirable even for a short time – for example, schools, call centres, some offices and cinemas.
THERMAL BRIDGE Thermal bridges occur where the insulation layer within the building envelope is penetrated by a material with a relatively high thermal conductivity and at interfaces between building elements where there is a discontinuity in the insulation. Thermal bridges result in heat losses and lower internal surface temperatures around the bridge, which may lead to condensation. Repeating thermal bridges, such as C sections located with the insulated layer of light steel walls or brick ties, should be included in the U-value of the planar element. Non-repeating thermal bridges, such as floor junctions, windowsills and ridges, form additional heat transfer paths that are not accounted for in the elemental U-value. These are accounted for in energy performance assessments by the linear thermal transmittance ( Ψ -value) for each thermal bridge. In Approved Document L1a (effective on 15 June 2022) 4.16 advises: The designer and installer should review drawings to check that junctions are buildable and to ensure construction sequencing is carefully considered for each detail. PHOTOGRAPHIC EVIDENCE Section 4.17 (b) of Approved Document L1a states that before elements are concealed by subsequent work, an on-site audit should be undertaken to confirm that the designed details have been constructed. Photographs of the details should be taken in line with Appendix B. The photographs should be sufficiently detailed to show what has been installed and that it uses the materials specified in accordance with the agreed detail. Geolocation should be enabled to confirm the location, date and time of each image.
CONSERVATION OF FUEL AND POWER
PART L Part L of the Building Regulations for England and Wales (Conservation of fuel and power); Technical Booklet F1 and F2 for Northern Ireland (Conservation of fuel and power); and Section Six (Energy) of the Scottish Standards set the levels of thermal insulation required when carrying out building work, either for new build or refurbishment projects. These are expressed as a U-value that needs to be achieved. The required U-value will depend on the location of the project (England, Scotland or Wales), type of building (domestic or non-domestic) and application (floor, wall or roof).
U-VALUE A U-value (also known as planar thermal
transmittance) is a measure of the heat loss through a given area of a thermal element – for example, a wall, window or floor. Its units are expressed as Watts per metre squared per degree Kelvin (W/ m2K). The lower the U-value, the better insulated the element and, as such, more effective at preventing heat transfer. Refer to BR 443 Conventions for U-value calculations and BRE Digest 465 U-values for light steel-frame construction.
Ψ -VALUE (PSI) A Ψ -value (also known as linear thermal
transmittance) is a measure of the heat loss over a given length rather than area, at junctions between thermal elements – for example, where a floor joins an external wall and around openings. Its units are Watts per metre per degree Kelvin (W/mK). Lower Ψ -values mean less heat is lost through non- repeating thermal bridges.
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