Conventions for U-value calculations (2006 edition) BR 443
Note: This edition has been superceded by Conventions for U-value calculations (BR443 2e 2019).
BRE (Building Research Establishment) is an independent, research-based consultancy, testing and training organisation, operating in the built environment and associated industries.
Conventions for U-value calculations (2006 edition) BR 443, was written by Brian Anderson and published by BRE on 11 July 2006. The 44 page guide is in line with Part L of the Building Regulations (Conservation of fuel and power) which came into effect in April 2006.
U-values, (sometimes referred to as thermal transmittances and measured in W/m²K) represent how effective elements of a buildings fabric are as insulators. That is, how effective they are at preventing heat from transmitting between the inside and outside of a building. The lower the U-value of an element, the more slowly heat transmits across it, and so the better it performs as an insulator.
Calculation methods for U-values appropriate for demonstrating compliance with the building regulations are based on standards developed by the European Committee for Standardisation (CEN) and the International Organisation for Standardisation (ISO) and published as British Standards. They may be used for the relevant calculations by the Standard Assessment Procedure (SAP) for dwellings or by the Simplified Building Energy Model (SBEM) for other buildings.
Conventions for U-value calculations provides guidance about the calculation of U-values for architects and specifiers:
- It explains the different methods for calculating the U-values of roofs, walls, floors, basements, windows and doors.
- It provides detailed guidance about using those methods.
- It provides data relevant to typical UK constructions.
- It provides guidance about the thermal conductivity of materials.
- It provides guidance about issues that commonly arise when calculating U-values and how these apply to different construction types.
The contents of the guide include:
- Introduction.
- Numerical methods and simplified methods.
- Thermal properties of materials and products.
- Issues concerned with U-value calculations.
- Elements adjacent to an unheated space.
- Expression of results.
- U-values for walls.
- U-values for roofs.
- U-values for floors.
- U-values for basements.
- U-values for windows, roof windows and rooflights.
- U-values for doors.
- Appendix A: Elements adjacent to an unheated space.
- Appendix B: U-values of uninsulated floors.
- References and further reading.
[edit] Related articles on Designing Buildings
- Approved document L.
- BRE articles on Designing Buildings Wiki.
- Building regulations.
- Building Research Establishment.
- Conventions for calculating linear thermal transmittance and temperature factors.
- Conventions for U-value calculations (BR443 2e 2019).
- Energy performance certificate.
- Insulation.
- Kappa value.
- Simplified Building Energy Model.
- Standard Assessment Procedure.
- Thermal bridge.
- Thermal mass.
- U value.
- U-value conventions in practice: Worked examples using BR 443.
- What do design professionals need to know about U-value calculation conventions?
Featured articles and news
Download your free guide.
Four new types of prior approval for solar developments
Online Planning Portal application types from 5 September.
Election fails to spark construction industry revival
Contract awards and planning; post election.
Making diversity and inclusion easy for SMEs
The CIOB tool for companies with limited resources.
Sustainable Futures: Redefining Retrofit for Net Zero Living
BSRIA Briefing 2024, initial speakers announced.
Looking back at the UK's first Passivhaus leisure centre
Reflections on St Sidwell’s Point with CIAT.
A-Level results and electrical apprenticeships
Electrical Skills Index highlights areas with skills shortages.
One of the world's more unusual drive-throughs.
A quick introduction.
Hadrian's Wall Path and the national trails
The trails are heritage assets in their own right.
Articles on timely advice and hydraulic lime.
Building Designers Association of Australia
CIAT and BDAA sign Memorandum of Understanding.
Built Environment Inclusive partners issue statement committed to inclusion.
Building regulation requirements can have unintended consequences.
CIOB announces 2024/25 vice president
Sustainability champion Professor Saul Humphrey.
Accelerating towards a net-zero built environment.