West-facing apartments pose greatest heat risk during French heatwave

Urban planning expert Clément Gaillard explains that west‑facing façades receive very little sun in winter but large amounts in summer, especially during a heat wave. The solar energy hits the façade in the late afternoon when indoor temperatures are already high, and glass lets through nearly 100 times more energy than solid walls, making overheating likely. Gaillard notes that the solar power reaching a west façade can be up to three times greater in summer than in winter, and apartments oriented solely to the west have limited ventilation, intensifying the heat buildup.

He warns that this exposure creates a “thermal trap” for occupants, turning what is marketed as a desirable view into a significant comfort and health issue during extreme temperatures.