SAP Assessments & New Build EPCs (Part L Compliance)

A SAP assessment is required for most new dwellings in the UK and is used to demonstrate compliance with Part L of the Building Regulations (Conservation of Fuel and Power). SAP calculations are also used to generate new build Energy Performance Certificates (EPCs).

Saxon Surveying provides SAP assessments for new build houses, flats, and residential conversions, with clear outputs suitable for Building Control approval.

What is a SAP assessment?

SAP (Standard Assessment Procedure) is the UK Government’s approved methodology for assessing the energy performance of new dwellings. Unlike EPCs for existing homes, SAP is a design-based calculation, using construction details and specifications rather than a physical survey alone.

SAP assessments:

Calculate a dwelling’s energy efficiency and carbon emissions
Demonstrate compliance with Part L requirements
Produce the new build EPC at completion

When is a SAP assessment required?

SAP assessments are typically required for:

New build houses and flats
Residential conversions (e.g. barns, offices to dwellings)
Change of use creating new dwellings
Certain major extensions or alterations where Part L is triggered

If a project creates a new dwelling or materially alters energy performance, Building Control will usually require SAP documentation.

SAP assessments and Building Regulations (Part L)

Part L of the Building Regulations sets minimum standards for energy efficiency in new dwellings. SAP assessments are used to demonstrate compliance by comparing:

Dwelling Emission Rate (DER) against
Target Emission Rate (TER)

If the proposed design does not meet Part L targets, changes may be required to insulation levels, glazing, heating systems, or renewable technologies before approval.

The SAP process explained

A SAP assessment is usually carried out in two key stages:

1. Design-stage SAP (Pre-construction)

Based on architectural drawings and specifications
Confirms whether the design meets Part L requirements
Produces compliance outputs for Building Control

2. As-built SAP & New Build EPC

Updated using final construction details
Produces the official EPC
Submitted to Building Control on completion

What information is needed for a SAP assessment?

To complete a SAP calculation, we typically require:

Architectural plans and sections
Construction details (walls, floors, roofs)
Window and door specifications
Heating and hot water system details
Ventilation strategy
Renewable technologies (if applicable)
Air-tightness test results (where required)

Early involvement can often reduce delays and design changes later.

What we provide

Our SAP service includes:

Design-stage SAP calculations
Part L compliance outputs for Building Control
As-built SAP updates
New build EPC production
Clear guidance if design changes are needed

We work with homeowners, developers, architects, and builders to keep projects moving smoothly.

SAP vs EPC – what’s the difference?

SAP is a calculation method used for new dwellings
RdSAP EPCs are used for existing homes
SAP assessments result in a new build EPC, but they are not interchangeable

If you’re unsure which applies to your project, we can advise before work begins.

Why choose Saxon Surveying?

SAP assessments carried out to current UK standards
Clear, practical advice for compliance
Experience with new builds, conversions, and residential developments
Straightforward communication with designers and Building Control
Local knowledge and reliable turnaround

Speak to us about SAP assessments

If you’re planning a new dwelling, conversion, or project requiring Part L compliance, we can help.

Talk to us about SAP Assessments Or return to our main overview: EPCs