The role of dynamic primary energy factors (PEFs) in building performance assessment: A case study

The adoption of primary energy factors (PEFs) is very common in the building sector since primary energy is one of the main metrics for evaluating the energy performance of a building. The use of such factors is extensive in European and international legislative contexts to establish a regulatory framework for enhancing building energy efficiency policies. This study analyses how the use of dynamic PEFs, variable on an hourly basis, affects the assessment of building performance. The dynamic primary energy factor for electricity has been evaluated for the Italian scenario during the year 2022, applying the methodology outlined in the EN 17423:2020 standard with an hourly detail. The conversion factor was subsequently applied to the electricity demand of a reference building for residential use. The result obtained has been compared with the same evaluations carried out using the static conversion factors currently adopted by the legislation in force, showing that there is an urgent need for adjustment. The dynamically assessed total PEF stopped at an average value of 1.84, in contrast to the 2.42 used in current legislation. As a result, the total primary energy demand of a reference building decreases by 23.07%, also involving an alteration of the ratio of renewable to non-renewable share. The study concludes that the use of dynamic PEFs is essential for both the design of new buildings and the assessment of existing buildings, especially when time-dependent HVAC, renewable energy and control strategies are considered. It also allows for better energy flow management within buildings. Finally, the study emphasizes that up-to-date PEFs are crucial for improving the energy efficiency of buildings and guiding the future decarbonization of the building stock.