What are SAP Calculations?

What is SAP?

The Standard Assessment Procedure (SAP) is the UK Government's recommended methodology for measuring the thermal efficiency of residential buildings. The first version was published in 1995 and subsequently replaced by newer versions in 1998, 2001, 2005, 2009 and most recently 2012. It calculates the typical energy usage for space and water heating. The COemissions are also calculated as part of the process.

SAP 2005 was the basis for checking new dwellings for compliance with Building Regulations in the UK in respect of the conservation of fuel and power since 6 April 2006 (England & Wales: Approved Document L1), 1 November 2006(Northern Ireland Technical Booklet F1) and 1 May 2007 (Scotland Technical Handbook 6, Domestic). SAP2009 was in force from 1st October 2010 and was replaced by SAP 2012 on 6th April 2014, with a further tightening of standards.

Stringent new regulations are imminent with the Government's Future Homes Standard expected to be finalised soon.


We are having an extension built, does this need a SAP Calculation?

Increasingly yes, especially if there is a high level of glazing (over 25% of the floor area) in the extension, the architect or builder should  arrange for the detailed SAP Calculations to be completed in order to show that the completed dwelling complies with Building Regulations in terms of new or upgraded thermal elements.

In certain circumstances this may be demonstrated by calculating area weighted u-values for the thermal elements. However if this approach is not applicable then compliance may be demonstrated on the basis of a whole house calculation where the existing house plus the proposed extension must have lower emissions than the existing house plus a notional extension built to reference values. This can sometimes provide the flexibility to upgrade parts of the existing house to help achieve compliance and of course we will give you the necessary advice to help you achieve compliance. 

It is advisable to have these calculations done at an early stage in the build to avoid costly changes to achieve Building Regulations compliance. Building Control Officers are asking for calculations for many more extensions and this will increase further when the new Building Regulations come into force Don’t get caught out! It can be costly to make changes to achieve compliance once construction is advanced.


We are having a new house built and have been told we need to get SAP Calculations done before the Building Control Officer will give approval?

That’s correct. SAP or Standard Assessment Procedure is the method used whereby the thermal efficiency of a dwelling is calculated from the plans and specifications. 

It ia normally done in two stages; firstly at the ‘Design’ stage, submitted with the initial Building Regulations submission for approval by the Building Control Officer before any works commence and then again at the ‘As Built’ stage, within 5 days of completion of the project when the calculations are submitted for the BCO to sign off (you will not be able to sell the dwelling without this completion certificate!).  


Remember: You will need SAP Calculations and an On Construction EPC for new builds and conversions before Building Control sign off. Without sign off you will be unable to complete a sale!