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Standard Assessment Procedure

Standard Assessment Procedure (SAP)

The Standard Assessment Procedure (SAP)represents the government's chosen methodology for calculating the energy efficiency and carbon dioxide emissions of residential buildings and new homes. The calculation is used to ensure the property complies with Building Regulations 2000 (Part L - Conservation of fuel and power) for England and Wales and provides energy performance ratings (EPR) for Energy Performance Certificates (EPC). It is the only calculation methodology available for new homes.

Within the Code for Sustainable Homes (CSH), SAP is used to calculate Dwelling Emission Rate (DER) and Target Emission Rate (TER) which both influence the overall sustainability rating of the home.


SAP was introduced in 1993 and now forms the basis of a number of Government energy and environmental policy initiatives, including the Code for Sustainable Homes, Energy Performance of Buildings Directive and Building Regulations for England.

SAP 2001 was published in December 2001 and became operational in Scotland from 4th March 2002 and within England and Wales from 1st April 2002.

SAP 2005 is the current standard for energy performance assessment calculations within England, Wales, Scotland and Northern Ireland.

A review of a draft SAP 2009 document was undertaken in 2009 with the new revised version of SAP (SAP 2009), envisaged to be published in 2010. Factors invited for comment in the draft document included revisions in the assessment of domestic hot water efficiency, internal heat gains, allowance for the impacts of thermal mass and the addition to include impacts of space cooling (air conditioning) within the methodology.


Indicators of energy performance are defined as:

  • Energy consumption per unit floor area
  • Energy cost rating
  • Environmental Impact Rating (EIR) based on CO2 emissions and a Dwelling Emission Rate (DER)

The SAP rating is based on the energy costs associated with space heating, ventilation and lighting, minus cost savings from energy generating technologies. The rating is adjusted for floor area, which makes building size virtually irrelevant.

SAP can be viewed as a measure of energy balance within a dwelling. The SAP calculation for energy performance criteria takes into consideration and includes data inputs from:

  • Materials used for the construction of the dwelling
  • Thermal insulation properties of the construction material
  • Ventilation characteristics of the dwelling and ventilation equipment
  • Efficiency and control of the heating system(s)
  • Solar gains through openings in the dwelling
  • Fuel used for heating (both hot water and rooms), ventilation and lighting
  • Renewable energy technologies

SAP calculation values are given on scale of 1 - 100. A value of 1 illustrates a poor standard with associated high running costs and low overall energy efficiency. A value of 100 signifies zero energy costs. SAP values greater than 100 signify that a home is a net energy exporter. An example SAP calculation is available for reference.

SAP methodology uses the Building Research Establishment Domestic Energy Model (BREDEM) to integrate data and generate energy performance ratings.

The latest version of SAP software can be found on the BRE Global website.

Environmental Impact Rate (EIR)

The Environmental Impact Rate (EIR) is based on annual carbon dioxide (CO2) emissions associated with space heating, water heating, ventilation and lighting minus emissions saved by energy generation technologies.

Dwelling Emission Rate (DER)

Dwelling CO2 Emission Rate (DER) is similar to the EIR. It is equal to the CO2 emissions per m2 of the floor area and the DER is used for the purpose of building regulation compliance.

Target Emission Rate (TER)

This is the maximum CO2 emission rate permitted by building regulations for the dwelling.