SAP Calculations

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.

Where we work

Everywhere in England and Wales, from the desk. A SAP calculation is a desktop assessment from your drawings and specification — there is no site visit in it — so where the site is makes no difference to how we do it or how quickly. We assess plots across England and Wales — London boroughs, the Midlands, the North, the South West — and the only local question that ever matters is which planning authority you are under, because a few of them ask for more than Part L.

London is the one that does it systematically: the London Plan’s 35% carbon target, borough energy statements and carbon offset payments sit on top of Part L for many schemes there, so it has its own page.

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.

SAP is rarely the only report a dwelling needs — see the full stack of compliance services for residential buildings if you want the lot priced together.

Need it fast? Ask about ASAP, our priority fast-track SAP service.