Conventions for Calculating Linear Thermal Transmittance and Temperature Factors

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 information needed by designers and numerical modellers to carry out these calculations, so that users of the same software package or users of different software packages can obtain 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 second edition has been comprehensively updated and includes:

- additional junction types with guidance on how they should be modelled

- 7 new worked examples giving the determined values of linear thermal transmittance and temperature factors.