Improving The Thermal Performance Of Buildings

Cold bridging – also known as thermal bridging – can be thought of as weak areas in the insulation system of a building.

In the fight to improve energy efficiency, due consideration should be given to ways in which we can reduce cold bridging, thereby increasing the effectiveness of insulation. Cold bridging occurs in any place where there is a potential break in the continuity of the insulation, where heat will leak out, such as studwork, steel wall ties, holes made to accommodate pipes, and junctions around walls, floors and roofs. While one way to deal with cold bridging is to consider it at the initial design stage, there are also many effective products on the market which help reduce the heat loss associated with existing features. The latest version of the Part L energy efficiency regulations include supplementary material entitled ‘Part L Accredited Details (AD)’ which gives advice on how to design a range of junctions to best minimise both cold bridging and heat loss. The Building Research Establishment (BRE) supports industry and clients to achieve good thermal performance in buildings through publications, consultancy, research and advice on building design and regulatory requirements. BRE supports industry to achieve good thermal performance in buildings through publications, consultancy and research and provides services to clients seeking advice on building design and regulatory requirements. Thermal Modelling Building regulations require that thermal bridging be taken into account in SAP and SBEM calculations. The junctions that need to be accounted for include wall-floor junctions, wall-roof junctions, lintels, jambs, cills, intermediate floors, balconies, corners, party walls and other significant junctions. Their effects are expressed in terms of Ψ- values, or linear thermal transmittance values, and, unless they are recognised Accredited Details, they should be evaluated using thermal simulation software, following agreed conventions and standards. BRE Scotland specialise in undertaking analysis of the thermal performance of buildings, building components, junctions, thermal bridge analysis and associated services leading to legislative compliance and improved energy performance calculations. Conventions For U-value Calculations (BR 443, 2006 Edition) There are various standards dealing with the calculation of Uvalues of building elements. The conventions provide guidance on the use of the standards, indicating the methods of calculation that are appropriate for different constructional types, providing additional information about using the methods and providing data relevant to typical UK constructions. The U-value conventions were originally published in 2002 and the 2006 edition is an update which provides additional information and reflects changes in the underlying British Standards. It can be downloaded as a PDF from bre.co.uk and it is also available as a printed booklet from BREbookshop.com Conventions for Calculating Linear Thermal Transmittance And Temperature Factors (BR 497) Amongst other measures that address the need to reduce CO2 emissions, that of having better insulated buildings requires more sophisticated methods such as numerical modelling to calculate the heat loss caused by thermal bridging at wall, roof and floor junctions and around openings. This guide gives the conventions that should be followed by numerical modellers to produce consistent, reproducible results. For building regulation purposes two key modelling outputs, temperature factor and linear thermal transmittance, are identified. These key outputs will enable designers to confirm the adequacy of particular junction details and help with the development of novel solutions to improve the thermal performance of junctions. This publication can be purchased from BREbookshop.com, and live updates to BR 497 can be found at www.bre.co.uk