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SAP stands for the Standard Assessment Procedure which the UK Government has adopted as the methodology for calculating energy performance in dwellings. This was introduced into the Building Regulations in 1995 as a vital step in the process of improving the energy performance and reducing the CO2 emissions.

The SAP methodology is used for self-contained domestic dwellings. In outline, the procedure:

Calculates the rate of heat loss from the dwelling, considering conduction and convection heat losses.

Determines the amount of heat required to maintain the dwelling at a comfortable temperature, given the rate of heat loss.

Determines the amount of energy required to provide hot water and lighting for the occupants.

Calculates the amount of energy required to provide the heat, hot water and lighting, given the efficiency of the building services, such as the boiler.

Calculates the cost of that energy, based on standardised fuel costs; and,

Calculates the carbon dioxide emissions based on standardised emission rates.

The procedure also considers; the area and volume of the building, the materials used, the thermal insulation, the thermal mass, ventilation, efficiency of heating controls, solar gains, the fuel used and any renewable technologies.

With over 40% of energy use in the EU being directly attributable to the operation of buildings, and 44% of the UK carbon emissions coming from buildings, addressing energy use and emissions in buildings therefore has the potential to make a substantial difference to overall energy and emissions in Europe.

The last government made a legally binding commitment to address the greenhouse gas emissions by 80%, relative to 1990 levels by 2050. Therefore, passing SAP is becoming more difficult with more stringent regulations now in force.