Standard Assessment Procedure

Overview

The Standard Assessment Procedure (SAP) is the methodology used by the government to assess and compare the energy and environmental performance of dwellings. Its purpose is to provide accurate and reliable assessments of dwellings that are needed to underpin energy and environmental policy initiatives. The Simplified Building Energy Model (SBEM) is the methodology used by the government to assess and compare the energy and environmental performance of non-domestic properties.

The government is committed to increasing the accuracy of SAP. The most recent version of SAP 10 (10.2) came into force with the updated Part L building regulations in June 2022, and incorporated various changes to the methodology, including updated:

• fuel prices
• CO2 emissions
• primary energy factors

For existing dwellings, a simplified version of SAP called Reduced Data SAP (RdSAP) is used to assess their energy performance. An RdSAP assessment will use a set of assumptions about the dwelling based on conventions and requirements at the time it was constructed.

RdSAP 2012 is the current version used to produce assess energy performance in existing dwellings. The government is working on an RdSAP update (RdSAP 10.2) which we expect to publish in due course.

Background

SAP was developed by the Building Research Establishment (BRE) for the former Department of the Environment in 1992, as a tool to help deliver its energy efficiency policies. The SAP methodology is based on the BRE Domestic Energy Model (BREDEM), which provides a framework for calculating the energy consumption of dwellings.

In 1994 SAP was cited in Part L of the Building Regulations as a means of assessing dwelling performance. Reduced Data SAP (RDSAP) was introduced in 2005 as a lower cost method of assessing the energy performance of existing dwellings. SAP and RDSAP are used to underpin the delivery of a number of key energy and environmental policy initiatives, for example:

• to demonstrate that new dwellings comply with the Building Regulations
• Energy Performance Certificates (EPCs)
• the SAP methodology underpins the EPC, which can only be produced by a qualified and accredited assessor

How SAP works

SAP works by assessing how much energy a dwelling will consume when delivering a defined level of comfort and service provision. The assessment is based on standardised assumptions for occupancy and behaviour. This enables a like-for-like comparison of dwelling performance. Related factors, such as fuel costs and emissions of carbon dioxide (CO2), can be determined from the assessment.

SAP quantifies a dwelling’s performance in terms of:

• energy use per unit floor area
• a fuel-cost-based energy efficiency rating (the SAP Rating)
• emissions of CO2 (the Environmental Impact Rating)

These indicators of performance are based on estimates of annual energy consumption for the provision of space heating, domestic hot water, lighting and ventilation. Other SAP outputs include:

• estimate of appliance energy use
• the potential for overheating in summer
• the resultant cooling load

Future developments - SAP 11

In 2020 we commissioned a scoping project for the next version of SAP - SAP 11 - to advise on how it can be enhanced to support net zero commitments for buildings. A consortium led by Etude carried out the SAP 11 scoping project which made a number of recommendations, including how to make SAP more accurate, robust and fit for purpose to support the net zero commitment.

In October 2021 we appointed a consortium of experts led by the Building Research Establishment (BRE) to develop SAP / RdSAP 11. The SAP 11 project team is working with stakeholders to consider the Etude recommendations and how to implement them. We look forward to engaging further with industry through our SAP 11 consultation which we plan to launch next year.

SAP 11 will come into force in 2025, alongside the Future Homes Standard update of the Building Regulations.