In major metropolises like Paris or Lyon, peak temperatures have already approached 40°C during recent heat waves, and climate forecasts indicate that these episodes will become the norm within a few decades. However, most buildings are not subjected to thermal resilience tests at this level, leaving residents vulnerable to extreme heat that exceeds the insulation and ventilation capacities prescribed by current standards.
Current constructions and their limits at 40°C
Edouard Dequeker and Alireza Razavi point out in their opinion piece that the processes for obtaining building permits do not include any validation of habitability at 40°C. The specifications for most programs only mention thresholds of 25°C, while satellite data from Copernicus shows urban heat islands where surface temperatures far exceed this ceiling. Without reinforced thermal performance requirements, new residences risk becoming ovens during the first hours of a heat wave.
The lack of consideration for these extremes also translates into undersized air conditioning systems. According to Météo France, energy consumption peaks during heat waves increase by 30% to 50% depending on the region, and electrical networks already struggle to absorb these overloads. A neural network applied to consumption data could anticipate these peaks, but predictive models remain underutilized in urban planning.
In practice, most construction projects continue to use standard materials like concrete and steel, which retain heat and slow down nighttime cooling. The absence of an adapted thermal insulation layer, combined with single-glazed windows, creates a local greenhouse effect that amplifies occupant discomfort. Without a revision of construction standards incorporating 40°C scenarios, future homes could become uninhabitable without systematic air conditioning.