BRE's expertise in thermal performance
BRE is the world’s largest research and technology organisation offering expertise in every aspect of the built environment and associated industries. We help clients create better, safer and more sustainable products, buildings, communities and businesses - and we support the innovation needed to achieve this. BRE are expert in the area of thermal performance of building fabric, and have consistently delivered for both public and private sector organisations in this area.
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 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 the BREbookshop.com
Updates to BR 497 can be found at Live updates to BR497
Conventions for U-value calculations
There are various standards dealing with the calculation of U-values 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 original 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 using the link on the right and it is also available as a printed booklet from BREbookshop.com
Thermal bridges in building construction - Heat flows and surface temperatures - Detailed calculations
(EN ISO 10211)
ISO 10211:2007 sets out the specifications for a three-dimensional and a two-dimensional geometrical model of a thermal bridge for the numerical calculation of:
- Heat flows, in order to assess the overall heat loss from a building or part of it
- Minimum surface temperatures, in order to assess the risk of surface condensation
These specifications include the geometrical boundaries and subdivisions of the model, the thermal boundary conditions, and the thermal values and relationships to be used.
BRE were involved in the development of EN ISO 10211.
Use of thermal imaging to determine the thermal performance of buildings
Infrared thermography is the analysis of thermal information from non-contact thermal imaging devices. It provides a visual representation of surface temperature and from this heats flow through the building fabric can be implied.
BRE offers thermal imaging of building fabric according to BS EN13187 and BRE 176. Our Thermographers hold Level 2 certification in Thermography and we use advanced thermal imaging cameras.
Thermal imaging of building fabric helps to;
- Identify areas of missing/defective insulation
- Identify thermal bridges
- Identify areas at risk from mould and condensation
- Provide quality control following the installation of insulation
- Satisfy requirements for BREEAM Assessments (Management Man 01: Sustainable procurement ) which states;
- The main contractor accounts for a thermographic survey within the project budget and programme of works.
- Once construction is complete a thermographic survey of the building fabric is undertaken in accordance with the appropriate standard and by a professional holding a valid Level 2 certificate in thermography.