The Standard Assessment Procedure (SAP) is the UK government’s recommended method system for measuring the energy rating of residential dwellings. The first version was published in 1995, and was replaced by newer versions in 1998, 2001, 2005, 2009 and 2012. It calculates the typical annual energy costs for space and water heating, and, from 2005, lighting. The CO2 emissions are also calculated. The SAP runs from 1 to 100+, with dwellings that have SAP>100 being net exporters of energy.

SAP 2012 has been used as the basis for checking new dwellings for compliance with building regulations in the United Kingdom requiring the conservation of fuel and power since 6 April 2014 in England or 31 July 2014 in Wales.

A reduced data version of SAP, RDSAP, is used for existing dwellings. SAP or RDSAP was used to produce the energy report and Energy Performance Certificate in Home Information Packs (HIPs). A document was published by the UK government in 2007, looking towards SAP and energy standards in the future.

A number of comparisons have indicated that SAP does not provide an accurate model for low-energy buildings.

The Standard Assessment Procedure evolved from the National Home Energy Rating scheme, which was based upon the Milton Keynes Energy Cost Index created for the Energy World demonstration buildings in the 1980s.

Part L. Conservation of fuel and power

Approved documents L1 is specific to dwellings and L2 relates to all buildings other than dwellings.

As of 6 April 2006 (2010) (2014) split into four sections:

  • L1A New dwellings
  • L1B Existing dwellings
  • L2A New buildings other than dwellings
  • L2B Existing buildings other than dwellings

Part L controls the insulation values of building elements, the allowable area of windows, doors and other openings, air permeability of the structure, the heating efficiency of boilers and the insulation and controls for heating appliances and systems together with hot water storage and lighting efficiency. It also sets out the requirements for SAP (Standard Assessment Procedure) calculations and carbon emission targets for dwellings.

Regulation 16 requires the advertising of the SAP rating in all new dwellings, and in the EPC document.

Approved Document L1 is supported by a set of ‘robust’ construction details, now known as “Accredited Construction Details”.[10] which focus on way of limiting air leakage and thermal bridging in construction. By using these tried and tested details, expensive on-site testing can be avoided.

In addition to insulation requirements and limitation of openings of the building fabric, this part considers solar heating and heat gains to structures, it controls heating, mechanical ventilation and air conditioning systems, lighting efficiency, space heating controls, air permeability, solar emission, the certification, testing and commissioning of heating and ventilation systems, and requirements for energy meters.

Air permeability is measured by air tightness testing for new dwellings (based on a sampling regime), all new buildings other than dwellings and large extensions to buildings other than dwellings.

These four Approved Documents must be read in conjunction with the supplemental official and industry documents (the ‘second tier’ guidance documents).


  1. ^ Approved Document L1A: Conservation of fuel and power (New dwellings) (2006 edition). Department for Communities and Loc Government. 15 March 2006. ISBN 978-1-85946-217-1.
  2. ^ The Government’s Standard Assessment Procedure for Energy Rating of Dwellings, version 2012
  3. ^ SAP Calculations Explained
  4. ^ Building Regulations: Energy efficiency requirements for new dwellings – A forward look at what standards may be in 2010 and 2013. Department for Communities and Local Government. 23 July 2007. 07 HC 04748/F.
  5. ^
  6. ^ Passivhaus project reveals flaws in Code
  7. ^ Raising the bar

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