Assessing Standard Assessment Procedure (SAP): Low cost measurement-based alternatives to SAP in housing

The objective of this paper is to investigate a simple and low cost method that could give quick and reliable information about the energy performance of homes and could replace costly on-site assessments. Our approach is based on internal and ambient temperatures only. The indoor temperatures of 20 homes located in the South of England were recorded over a period of one week during the heating season. From the temperature profile of each home the temperature decay periods were identified and the overall leakage rate of the building was estimated. These leakage rates, which are an indicator of the actual heat loss of a building, were compared with (a) the overall heat transfer coefficient estimated though Standard Assessment Procedure (SAP) and (b) the actual heating demand normalised for weather data. Other comprehensive datasets such as ambient temperatures and gas bills were used to complete the analysis. Initial results show that there is a weak correlation between the heat loss estimated through SAP and the leakage rates. A weak correlation was also found between actual consumption for space heating and the leakage rates. The analysis was performed using the average leakage rate of each house based on the complete weekly temperature profile and the average leakage rate of each house based on the night periods only. Results indicate that the dominant factor on leakage rates and therefore annual energy demand for space heating is occupant behaviour in respect to ventilation in particular.