Part L1 SAP Calculations & EPC

Walker Energy Analysis provides SAP calculations and EPCs for new build and conversion dwellings across the UK, with our accredited On Construction Domestic Energy Assessors. We provide Part L1 compliance through from the design stage calculation to the as-built assessment and the EPC that follows from it.

SAP for New Build and Conversions

SAP, the Standard Assessment Procedure, is the methodology used to assess Part L1 compliance for new dwellings, and for conversions creating a new dwelling from a building not previously used as one. As an accredited OCDEA, this is what our accreditation covers, and it’s what we assess from design stage through to completion.

Design Stage and As-Built, Both Covered

Part L1 compliance is checked at two points, and both carry their own SAP calculation.

The design stage SAP calculation is produced before construction begins, based on the specification as drawn, and confirms the target and predicted dwelling emission rates and primary energy rates meet target.

The as-built SAP calculation is produced once construction is finished, using the measured air permeability and any specification changes made on site, and this is what the final EPC is generated from. Building control checks the as-built figures against the design stage submission, so any drift between what was specified and what was actually built shows up here.

SAP calculations for new build and conversion dwellings
Design stage assessment for building control notification
As-built assessment, incorporating measured air permeability and construction changes
EPC production and lodgement, direct from the confirmed as-built calculation
Accredited OCDEA assessment, covering the full new build and conversion process

Working at Any Design Stage

Design Stage / Pre-Construction: full SAP calculation for building control notification, based on the proposed specification.

As-Built / Completion: updated SAP calculation reflecting the completed dwelling and measured air test results, plus the resulting EPC.

Mid-Project Design Changes: fast re-runs when specifications shift during construction, so the as-built calculation and EPC reflect what was actually built.

Why Work With Us

We’re a specialist energy consultancy, and an accredited OCDEA. This is the core of what we do, not a sideline. Every calculation runs through recognised SAP software as standard, we turn changes around quickly, and results come back in a format your team and building control can use immediately.

FAQs

Q: What counts as a qualifying conversion for SAP?

A: A conversion creating a new dwelling from a building not previously used as one, a barn conversion, or an office converted to residential use, for example, rather than works to a property that’s already a dwelling.

Q: Do you need two separate SAP calculations?
A: Yes, one at design stage before work starts, and one as-built, after completion, using the measured air permeability. The as-built calculation is what the EPC is generated from.

Q: When is the EPC generated?
A: From the confirmed as-built SAP calculation, once construction is complete and the measured air permeability is in.

Q: What happens if the specification changes during construction?
A: We update the as-built calculation to reflect what was actually built and confirm the dwelling still meets target. Any changes from the design stage specification are accounted for directly in the final figures.