Comparison of the Predicted Energy Savings Forecasted through an Environmental Performance Certificate (EPC) & EnergyPlus Building Simulation for a Retrofitted Domestic UK Property

In UK, about 30% of CO2 emissions come from the domestic sector. The government has therefore established the low carbon transitional plan in which encouraging to retrofit the existing housing market. In this context, solid wall dwellings have proved to be particular problematic due to the nature of their construction, and been considered as “Hard to Treat” (HTT) buildings. With consideration of cost-effectiveness and difficulty of implementation, applying insulation measures to increase the thermal efficiency of a house is the best and most effective way to reduce CO2. With the release of the UK ‘Green Deal’, finance will soon be available to citizens for insulation. However, there is concern that the savings projected through the current Standard Assessment Procedure (SAP) method, will not comply with the actual savings achieved. As SAP is based on a number of assumptions, one method to analyze the validity of this argument is through building simulation. A model was therefore built based on a HTT terraced house in Nottingham. This domestic rental property had one year of existing energy use data and a SAP based Energy Performance Certificate (EPC). This EPC methodology of energy assessment is planned to be used at a national scale with the implementation of the Government’s upcoming ‘Green Deal’. It is likely that the SAP based EPC assessment would not give as accurate result as the dynamic simulation alternatives. A model was therefore constructed and simulated using EnergyPlus. The results of the two methodologies are compared and are discussed within this paper. Variations in the results are likely to indicate implications to the large scale uptake of solid wall insulation in the UK, particularly if the savings indicated through SAP do not correlate with the actual.