A SAP calculation is required on new build properties, conversions and some extensions. This is the energy calculation on a domestic dwelling required by Part L of the building regulations.  

The SAP calculation calculates the total amount of CO2 (carbon dioxide) that the property produces. 

SAP stands for Standard Assessment Procedure and is the approved method for calculating the energy performance of a domestic dwelling. 

The SAP calculation is based on the volume of the property, all the main elements (floors, walls, roof, doors and windows), thermal bridging, insulation, heating and lighting. All of these items are input into the calculation with set standards for the u values or efficiencies. 

The SAP calculation is divided into separate sections for each element. Each element has stand-alone targets, with the individual and total sum creating the final result. 

SAP is a desk top calculation and is carried out from a set of drawings and specifications provided by the client. The SAP calculation for a new build property has two stages: the design stage SAP and the As Built SAP. 

The As Built SAP is an amended version of the Design stage SAP, but includes the actual products used rather than what is proposed. The As Built SAP also includes the air test result, rather than the target. 

The EPC (Energy Performance Certificate) is produced from the As Built SAP. Conversion SAP calculations must show efficiency standards and meet carbon standards. The process is similar, but the calculation is different, and only one calculation is carried out. Extension SAP Calculations require that the extension does not have more than 25% of the new floor area as new glazing. This is to show that the extension doesn’t make the existing property worse than it currently is with regard to solar gains. For this type of SAP calculation, you need to compare the existing building with the proposed building. 

ATSPACE energy assessors are fully accredited to help you achieve compliance in all types of SAP calculations.