What is a SAP calculation?
The Standard Assessment Procedure (SAP) is adopted by Government as the UK methodology for calculating the energy performance of dwellings.
The SAP rating is based on the energy costs associated with space heating, water heating, ventilation and lighting, less the emissions saved by energy generation technologies. It’s adjusted for floor area so that is it essentially independent of dwelling size 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 calculation is based on the energy balance taking into account a range of factors that contribute to energy efficiency:
- Materials used for construction of the dwelling
- Thermal insulation of building fabric
- Ventilation characteristics of the dwelling and ventilation equipment
- Efficiency and control of the heating system(s)
- Solar gains through openings of the dwelling
- The fuel used to provide space and water heating, ventilation and lighting
- Energy for space cooling, if applicable
- Renewable energy technologies
The calculation is independent of factors relating to the individual characteristics of the household occupying the dwelling when rating is calculated.
Information required for SAP calculation
- Site address and postcode.
- Site plan to include orientation of the dwelling(s).
- All plans relating to the project in PDF or preferably AutoCAD / REVIT format.
- Elevations drawings for each elevation.
- Sectional drawings of the dwelling.
- A written specification which must include:
- Details of the principal heating and hot water system to include make and model of boiler, details of heating emitters, hot water cylinder size (if applicable) and the system controls.
- Details of any secondary heating system present.
- Details of ventilation systems.
- Details of the internal and external lighting.
- Details of the construction of all different floors to the property to include type and thicknesses of insulation and any other building products used.
- Details of the construction of all different external walls to the property to include type and thicknesses of insulation and other building products used.
- Details of the construction of all different roofs to the property to include type and thicknesses of insulation and other building products used.
- Details of the doors and windows to include sizes, type of frame, type of glazing, thickness of glazing, any low emissivity applications.
- Details of any renewable technologies utilised such as ground source heat pumps, solar water heating or photovoltaics
Guidance on the specification can/will be available, however we recommend that the Architect and client discuss these points before contacting us.
Further information relating to SAP can be found here (link to SAP 2009)
Example SAP calculation here
Hints & Tips for SAP
- Consult a SAP Assessor at Planning stage. At this point the assessor can advise on construction to avoid any abortive work or architectural re-draw.
- Give thought to ventilation + heating prior to approaching the SAP assessor.
- Be prepared existing regulations may require renewables to be applied. This could possibly result in a choice of implementing Air Source heat pump or Solar PV.
- Assure that the individual (not the company) is accredited with the correct association for registering EPCS (Energy Performance Certificates). Don’t assume that someone conducting a SAP is necessarily registered to register an EPC, this is commonly not the case and can result in double the costs to get a registered person to re-do the calculation.
- Be aware that making changes out with the SAP during construction can result in the calculation possibly failing and alternative means having to be applied at high costs and resulting in the verifier rejecting any completion certificates.
- Make sure the property has a UPRN (Unique Property Reference Number) acknowledged by the Energy Saving Trust.
A UPRN is a unique alphanumeric identifier for every spatial address in Great Britain and can be found in OS’s Address products.
EPC sign off sheet here Confirmation required of as built construction before EPC can be generated.
Example EPC here