In France, 50% of buildings are not adapted to heatwaves

France’s heatwave problem is increasingly a housing problem.

A researcher at France’s Scientific and Technical Center for Construction, or CSTB, told Le Monde that about 50% of the country’s buildings are not adapted to heatwaves. The estimate amounts to roughly 10 million buildings and comes as France faces another exceptionally early heatwave and as ministers defend their climate adaptation plan.

How CSTB is measuring the risk

Julien Hans, CSTB’s director of research and innovation, said the institute uses the National Building Database, known as BDNB, to simulate a heatwave similar to the one that hit France in 2003. That modelling helps identify buildings most likely to overheat and gives public actors a way to target the worst cases.

Hans said the tool is used to help the French government, local authorities, social housing providers, nursing homes and schools focus on the sites most at risk. He said around 20% of buildings are the most vulnerable and can be prioritized first.

The problem is concentrated in urban areas and urban heat islands, where temperatures can stay high overnight and indoor heat can build up quickly. In that setting, building design becomes a public-health issue, not just a matter of comfort.

Who is most exposed

Schools, nursing homes and social housing are among the highest-priority buildings because their occupants can be especially vulnerable during heatwaves. Children, older people and residents in care settings are less able to manage prolonged indoor heat, which makes overheating inside these buildings a direct safety concern.

Hans said summer comfort should be included in renovations, but there is currently no regulation requiring it. That leaves many retrofit efforts focused on winter energy performance while ignoring how buildings behave during hot weather.

He also said France’s current pace of around 100,000 high-performance renovations a year would take several centuries to renovate the whole building stock. The gap matters because hotter summers are expected to make overheating a recurring problem rather than an exceptional one.

The policy backdrop

The CSTB warning lands during a new round of heatwave pressure for France. Le Monde reported on June 16 that the country was bracing for an exceptionally early second heatwave before summer, with temperatures forecast to reach 34C to 40C and possible peaks near 40C around the summer solstice.

On June 18, Le Monde reported that the French government was presenting its third National Climate Change Adaptation Plan while 26 departments were under orange heatwave alert. The government said 85% of the plan’s actions had been launched, but the same reporting highlighted strain on adaptation financing.

That coverage said the Green Fund had fallen from €2.4 billion in 2024 to €837 million in 2026. The budget decline adds pressure to prove that adaptation policy can move beyond announcements and into concrete building upgrades.

What can be done now

Hans pointed to relatively simple passive measures that can reduce indoor heat, including shutters or other sun protections, fans and nighttime ventilation. Those steps can make a difference quickly, especially in buildings that are hardest to retrofit immediately.

But the broader challenge is structural. France is still renovating far too slowly to keep pace with a warming climate, and many buildings were designed for conditions that no longer fit the heat people now face each summer.

The result is a policy problem that runs across housing, public buildings and health protection. As heatwaves intensify, the question is no longer whether buildings matter in climate adaptation, but how quickly France can make its housing stock, schools and care facilities safer.

For now, the warning from CSTB is blunt: a large share of France’s buildings are still built or managed as if summer overheating were a marginal issue. The next heatwave is testing that assumption in real time.