Should the DPE be reformed to better account for 'thermal reservoirs'?

During recent intense heatwaves, certain homes in France experienced indoor temperatures soaring to as high as 40 degrees Celsius (104 degrees Fahrenheit). This phenomenon has raised questions about the adequacy of the current energy performance diagnostic (DPE) system in reflecting the reality of housing conditions during extreme weather.

The DPE, a mandatory assessment of a building's energy consumption and greenhouse gas emissions, currently focuses primarily on heating efficiency and insulation against cold. However, the recent extreme heat events suggest that the diagnostic may not sufficiently account for dwellings that act as 'thermal reservoirs,' trapping heat and becoming dangerously hot during summer.

This oversight has prompted discussions about reforming the DPE. The proposed changes aim to incorporate a more nuanced evaluation of a home's performance in high temperatures, ensuring that the diagnostic provides a more accurate picture of habitability and energy efficiency across all seasons. The goal is to better protect residents from overheating and to guide more effective retrofitting strategies for buildings.