SAP Calculations for new build residential developments should be completed alongside the detailed design process, once internal layouts have been confirmed, and a provisional or outline build specification is available. This provides an opportunity to easily adopt any recommended specification changes that may be required to achieve compliance with Approved Document L: Volume 1 of the Building regulations (or other local equivalent standards). Once the building works are complete, the design stage SAP calculation is updated to reflect the completed dwelling including any specification or design changes, the final heating, hot water and ventilation systems and the actual measured air permeability rate of the residence as determined by an Air Tightness Test. The final ‘As Built’ SAP calculation is issued for submission to the appointed Building Control Body. It is also used to produce an On Construction Energy Performance Certificate (EPC) for the completed dwelling which is also required by Building Control as part of the sign off procedure, while also being a legal requirement for the subsequent sale let of the dwelling.