Evaluation of passive solar calculations in SAP

The Government's Standard Assessment Procedure (SAP) for the energy rating of dwellings, in the Building Regulations, is compared with detailed simulations using SERI-RES. The emphasis here is on the passive solar contribution to heating load. In this context the aspects of SAP being questioned are: the fact that solar gain and heating load refer to a single location (Sheffield); the fact that solar fluxes refer to October to April for a heating season of October to May; the limited window transmission coefficients; fixed percentage of frame; and neglect of solar gain on the walls and roof. Other aspects of SAP are: nonlinearity of heating load with heat loss, and neglect of uninsulated roof space. SAP is meant to be a rating system but the above points should be noted when values of solar gain or heating load are required.