UK Standard
CIBSE Domestic Heating Design Guide — Room Heat-Loss Method
CIBSE Domestic Heating Design Guide & Guide A (Environmental Design)
In short: The CIBSE method is the UK heating-engineering approach to calculating room heat loss from volume, fabric U-values, glazing, exposure and target temperatures — the basis for sizing radiators and heating systems.
What CIBSE Domestic Heating Design Guide covers
Published by the Chartered Institution of Building Services Engineers, it is the recognised reference for domestic heat-loss and radiator sizing in the UK.
Good practice adds a design margin (around 10%) over calculated heat loss to allow for cold snaps and radiator fouling over time.
Apply this standard
Calculators that use CIBSE Domestic Heating Design Guide
Official source: CIBSE — publications. Figures on this page are a plain-English summary for estimating purposes — always refer to the published standard for compliance.