They assess a home's annual energy use for heating, hot water, lighting, and ventilation based on standard occupancy and temperature settings. This allows for fair comparisons between different dwellings using an SAP Rating. SAP Calculations also estimate a property's annual CO2 emissions (Dwelling Emission Rate - DER) and its energy efficiency for the building itself (Dwelling Fabric Energy Efficiency - DFEE) and energy use from renewable sources (Dwelling Primary Energy Rating - DPER) - England only. In new builds, these figures must be lower than set limits (Target Emission Rate - TER, Target Fabric Energy Efficiency - TFEE, Dwelling Primary Energy Rating - DPER) to comply with building regulations (Approved Document L: Volume 1). Finally, SAP calculations are used to generate On-Construction Energy Performance Certificates (EPCs) for all new dwellings.

Early design stage: Once you have internal layouts and a basic building plan, it's ideal to complete your SAP calculations. Benefits of Early Completion: Easier to make adjustments if needed based on the assessor's recommendations. Fulfills most Building Control Body (BCB) requirements for design stage calculations before construction starts. Final Stage: After construction is complete, the initial SAP assessment is updated to reflect the final building ("As Built"). This final calculation is used to generate your On-Construction Energy Performance Certificate (EPC).

Your home's SAP Rating considers several aspects that influence its energy use and CO2 emissions: Building Features: Location, orientation, wall construction, window efficiency, air leakage (from air tightness test). Building Systems: Heating and hot water system efficiency (including fuel type), ventilation system type. Energy Use: Internal lighting usage, solar heat gain from windows. Renewables: Presence of renewable energy technologies. A higher SAP Rating indicates better energy performance.

For efficiency and to obtain an On-Construction EPC, a qualified and accredited On-Construction Energy Assessor is best. They're the only ones authorized to issue the final certificate. Our Recommendation: Choose an assessor with experience in all SAP versions and current Building Regulations to avoid costly mistakes during construction.