Last edited 14 Jul 2019

Standard Assessment Procedure SAP

The Standard Assessment Procedure for the Energy Rating of Dwellings (SAP) was developed by BRE based on the BRE Domestic Energy Model (BREDEM) and was published by BRE and the Department of the Environment in 1992. In 1994 it was first cited in Part L of the building regulations and it has now been adopted by the UK Government as the methodology for calculating the energy performance of dwellings.

The most recent version, SAP 2012, came into force for building regulations compliance on 6 April 2014. The 2009 version SAP 2009 may still be used on projects for which transitional arrangements apply, see 2013 changes to the approved documents for part L of the building regulations for more information.

In 2018, SAP 10 was published to allow comparisons with SAP 2012 and for understanding the methodological changes made ahead of any future use. As such, it is not a consultation version and SAP 2012 remains the version to be used until further notice. For more information, see Changes in SAP 10.

SAP provides a framework for calculating the energy performance of self-contained dwellings and individual flats (excluding common areas):

Energy consumption per unit floor area.
Energy cost rating adjusted for floor area (the SAP rating) expressed on a scale of 1 to 100, where a lower rating indicates higher running costs.
CO2 emissions adjusted for floor area (Environmental Impact rating or EI rating) expressed on a scale of 1 to 100, where a lower rating indicates higher running costs.
The Dwelling Emission Rate (DER) which is a similar indicator to the Environmental Impact rating, but where CO2 emissions are expressed in kg/m²/year.
The Target Fabric Energy Efficiency (TFEE) which is the minimum energy performance requirement for a new dwelling expresses as the amount of energy demand in units of kilowatt-hours per square metre of floor area per year (kWh/(m^2.year).

These calculations are based on:

Construction materials and thermal insulation of the building fabric.
Air leakage and ventilation equipment.
Efficiency and control of heating systems.
Solar gains.
Choice of fuel for space and water heating, ventilation and lighting.
Space cooling.
Renewable energy technologies.

SAP calculations are required to demonstration compliance with part L of the building regulations for new dwellings, new buildings converted to dwellings and some extensions and refurbishment work. Calculations should be carried out using a computer program approved for SAP calculations by BRE on behalf of the government.

The Dwelling Emission Rate (DER) is calculated based on the proposed design and specification for the dwelling. This is compared with a Target Emission Rate (TER), also calculated using SAP, but based on a notional dwelling of similar size and shape to the proposed dwelling. The TER sets the minimum acceptable standard of performance. The DER must not exceed the TER.

The Target Fabric Energy Efficency TFEE is the minimum energy performance requirement for a new dwelling. The Dwelling Fabric Energy Efficiency (DFEE) rate is the actual energy performance of the new dwelling. The DFEE must not exceed the TFEE. See Target fabric energy efficiency rate for more information.

A 'design' SAP report must be submitted as part of a building regulations application before construction begins. An 'as-built' SAP report must be submitted once the construction is complete, based on the actual design and specification that has been constructed, and taking into account air-leakage tests. An Energy Performance Certificate (EPC) must also be prepared.

The future development of SAP is likely to include consideration of feed in tariffs (FIT) and inclusion of on-site and off-site measures to mitigate carbon emissions to satisfy the government's target for zero-carbon homes by 2016.