33. Since 2012, the SHCS has collected enough information to derive a surveyed dwelling's heating system efficiency. For properties with boilers, comparing the efficiency against the minimum standards set by Scottish Building Standards provides an estimate of the domestic dwelling boiler stock compliant with current regulations, and offers another measure of Scotland's energy efficiency levels.
34. Heating system efficiencies are calculated by BRE and are provided for 2012 onwards based on a pre-control adjustment state (i.e. no adjustment is made for a poorly controlled system). In practice, where it has been possible to read an efficiency straight from the PCDB, this has been used. Alternatively, the SAP default has been used.
35. The efficiency cut-offs used to assess compliance of oil boilers with Scottish Building Standards reflect the different standards required of oil combination and oil non-combination boilers. Furthermore, while non-condensing boilers are present in the SHCS sample, the fuel dependent condensing boiler efficiency cut offs are applied for all boilers in the report when assessing building standard compliance.