Impact of the Accuracy of Geometrical and Thermophysical Inputs on EPC Asset Rating

EPC has converted itself in an instrument to guide the European Renovation wave and lead to decarbonisation of its building stock. To efficiently prioritize investments, it is key to have reliable EPCs that are representative of the true thermal performance of buildings and their systems. One of the sources of unreliability of EPC comes from the inputs used for the energy model. EPC’s inputs can be divided in two categories. First, geometrical data, linked with surfaces and volumes, have a big influence on the results of thermal models, therefore ensuring their adequate measurements is important. Second, thermophysical and system performance inputs generally use standard assumptions that do not reflect the reality of the building, as little information is available. Even if technical information is available, it does not reflect the quality of the constructive process. Using real energy consumption in realistic use conditions (weather, occupancy) to calibrate the thermal energy model can improve the reliability of the EPC results. Based on a study on 15 residential dwellings located in the northern Spain, the influence of different geometric measurement technics on EPC results has been studied, and recommendations to improve their accuracy are proposed. In addition, a methodology to calibrate thermophysical inputs of EPC models has been developed. It is based on automating the generation of detailed thermal model from inspection data, especially regarding HVAC systems. The study shows that differences in input can lead to up to two EPC category difference for the same residential building.