What is a SAP calculation?
A SAP (Standard Assessment Procedure) calculation is the methodology Building Control uses to check that a new dwelling complies with Part L of the Building Regulations. Dwelling data — areas, volumes, u-values, heating systems, renewables — is modelled against a ‘notional’ target dwelling. The dwelling passes when its CO₂ emissions (DER) and fabric energy efficiency (DFEE) beat the notional targets.
When do you need one?
- New build dwellings — design-stage SAP before work starts, as-built SAP plus EPC on completion.
- Conversions — barn conversions, office-to-residential, flat splits and similar changes of use.
- Over-glazed extensions — Building Control will ask for notional-vs-proposed SAP calculations if glazing exceeds 25% of the new floor area.
Why Energycount?
We assess hundreds of dwellings a year across the UK, advising from initial design through to completion — not just running the numbers, but helping specify the most cost-effective route to a pass. Thermal bridging is often the cheapest win: our ΨMonkey psi calculator lets us (and you) calculate accurate junction Ψ-values instead of using punitive defaults.
Need it fast? Ask about ASAP, our priority fast-track SAP service.