Residents of the Brazza eco-district in Bordeaux report that their energy-efficient apartments have become unbearably hot during a severe heatwave this week [1].
The situation highlights a potential failure in modern passive-cooling designs, which are intended to reduce energy use but may struggle against extreme temperature spikes.
Bordeaux has seen temperatures reach 40 °C [1]. This weather is part of a broader pattern, as France has experienced three heatwaves in the past two months [2].
Emerald Maxwell, a correspondent for France 24, said the apartment blocks were built to the latest standards. Maxwell said, "The apartment blocs are new, built to the latest standards – but inside it’s like an oven" [1].
The Brazza neighborhood was marketed as a sustainable development on the outskirts of the city. Despite the energy-efficient ratings of the walls, residents say the interior heat has become unmanageable. One unnamed resident said, "We’ve had enough – the heat inside our flat is unbearable, even though the walls are supposed to be energy‑efficient" [1].
Passive-cooling systems typically rely on thermal mass, and ventilation to regulate temperature without air conditioning. When external temperatures reach 40 °C [1], these systems can sometimes trap heat inside the building structure rather than repel it, leading to the "oven" effect described by the occupants.
Local residents are now questioning whether the latest construction standards are sufficient for the increasing frequency of extreme weather events in France [2].
“Inside it’s like an oven.”
This incident suggests a gap between theoretical energy-efficiency standards and the practical reality of extreme climate events. While passive-cooling is designed to lower carbon footprints by reducing reliance on air conditioning, these buildings may become uninhabitable if they cannot shed heat during prolonged, high-intensity heatwaves.
