Heatwave: Why are some recently built public buildings overheating?

The extreme heatwaves of recent weeks have highlighted a reality that is increasingly difficult to ignore: even newly constructed or renovated public buildings can experience significant overheating during the summer. The example observed in western France illustrates the new challenges facing architects, engineering firms, and local authorities.

A phenomenon that extends beyond Western France alone

While several buildings in western France have recently experienced unbearably high temperatures, experts point out that this is not a localized problem. The increasing frequency of heatwaves is calling into question many design choices made based on outdated climate models. A growing number of local authorities are commissioning assessments to evaluate the thermal vulnerability of their buildings.

Why can newer buildings overheat?

Contrary to popular belief, a new building is not automatically comfortable during periods of intense heat.

Several factors can contribute to overheating:

large glazed areas that are insufficiently protected;
absent or undersized external sun protection;
limited natural ventilation;
insufficient thermal inertia;
limited vegetation around the building;
uses which themselves generate heat inputs.

Added to this is a climate change that is happening faster than the assumptions made when designing many buildings built just a few years ago.

Local authorities must now incorporate summer comfort.

Long focused on winter performance and reducing energy consumption, the building must now meet a new requirement: maintaining an acceptable level of comfort during heat waves.

Schools, media libraries, sports facilities, administrative buildings, and healthcare facilities are directly affected. Their ability to remain usable during heat waves becomes a public health issue as much as a quality of use concern.

What levers can be used to better withstand heat waves?

Solutions exist and are primarily based on passive approaches:

external sun protection;
limitation of solar input;
night ventilation;
utilization of thermal inertia;
planting vegetation around the surrounding area;
materials better suited to high temperatures.

Air conditioning may be necessary in some sensitive buildings, but experts primarily favor a bioclimatic design that naturally limits overheating.

To remember

🌡️ Recent buildings They are not all suited to the increasingly frequent heatwave episodes.

🏫 Public buildings Schools, media libraries, sports facilities, and administrative buildings are particularly affected by the risks of overheating.

🌞 Summer comfort It is becoming an essential design criterion, on par with winter energy performance.

🏗️ Passive solutions Solar protection, natural ventilation, thermal inertia, and vegetation are the primary means of limiting overheating.

🌍 Climate change The climate references used in the design of many recent buildings no longer always correspond to current conditions.