SAP Explained

The Standard Assessment Procedure (SAP) is the UK Government’s methodology for assessing and comparing the energy and environmental performance of dwellings. Developed by the Building Research Establishment in 1992, SAP provides accurate and reliable assessments of dwelling energy performance.

SAP and Building Regulations

Part L of the building regulations has used SAP since 1994 to evaluate a building’s energy performance.

Waste Water Heat Recovery (WWHR) in SAP

SAP assesses the energy use of a dwelling while maintaining a defined level of comfort and service. It uses standardised assumptions for occupancy and behaviour, enabling like-for-like comparisons of dwelling performance.

Factors such as fuel costs and CO2 emissions are determined from the assessment. SAP quantifies a dwelling’s performance in terms of energy use per unit of floor area, a fuel-cost-based energy efficiency rating (SAP Rating), and CO2 emissions (Environmental Impact Rating).

WWHRS is a listed technology in the Products Characteristics Database (PCDB), which contains information on various technologies used within different National Calculation Methodologies (NCMs), including SAP and rdSAP. WWHRS targets energy use associated with hot water, particularly from showers, offering one of the highest cost vs SAP impact ratios.

• The SAP impact of WWHRS depends on several factors:
• Number of occupants calculated by SAP for the dwelling
• Total number of rooms for showering/bathing
• Number of rooms with WWHRS installed
• Whether the room has only a shower or a bath and shower
• The System (A/B/C) installation method used