SAP calculations explained in detail

The Introduction

SAP is the Government's Standard Assessment Procedure for Energy Rating of Dwellings. SAP 2005 is adopted by government as part of the UK national methodology for calculation of the energy performance of buildings. It is used to demonstrate compliance with building regulations for dwellings - Part L (England and Wales), Section 6 (Scotland) and Part F (Northern Ireland) - and to provide energy ratings for dwellings.

The indicators of the energy performance are energy consumption per unit floor area, an energy cost rating (the SAP rating), an Environmental Impact rating based on CO2 emissions (the EI rating) and a Dwelling CO2 Emission Rate (DER).
The SAP rating is based on the energy costs associated with space heating, water heating, ventilation and lighting, less cost savings from energy generation technologies. It is adjusted for floor area so that it is essentially independent of dwelling size for a given built form. The SAP rating is expressed on a scale of 1 to 100, the higher the number the lower the running costs.
The Environmental Impact rating is based on the annual CO2 emissions associated with space heating, water heating, ventilation and lighting, less the emissions saved by energy generation technologies. It is adjusted for floor area so that it is essentially independent of dwelling size for a given built form. The Environmental Impact rating is expressed on a scale of 1 to 100, the higher the number the better the standard.

The Dwelling CO2 Emission Rate is a similar indicator to the Environmental Impact rating, which is used for the purposes of compliance with building regulations. It is equal to the annual CO2 emissions per unit floor area for space heating, water heating, ventilation and lighting, less the emissions saved by energy generation technologies, expressed in kg/m²/year.
The methodology is compliant with the Energy Performance of Buildings Directive. The calculation should be carried out using a computer program that implements the worksheet and is approved for SAP calculations.

Bristol DEA uses Bre approved NHER SAP software on behalf of the Department for Environment, Food and Rural Affairs; the Department for Communities and Local Government; the Scottish Executive; the National Assembly for Wales; and the Department of Finance and Personnel).

The Data is collected from drawings, building notes and spec sheets, Data is then inputed into the accredited software by Authorised assessor and a draft report is created. If the design passes all criteria an As built final report is issued along with a Predicted Energy Performance Certificate (PEA) and submitted with main application to building control (prior to commencement of works).
If the project fails any of the criteria an accredited consultant shall redesign elements of the project in conversation with architect/client/builder in order to demonstrate compliance before submitting to building control. On-completion the architect / client / builder advises the Autherised assessor of any changes during the build, (if any) and provides the airtightness test result (where relevant). The assessor then produces the Asbuilt final SAP report and On construction energy performance certificate (OC-EPC) where relevant and submit both to building control for final sign off.