In order to combat the heat, companies and communities in France are repainting roofs and buildings white, which is a quick solution, but not a “miracle” to adapt to global warming.
By reflecting solar radiation, light colors avoid storing heat in the building envelope. Proponents of this solution easily cite, as ancestral examples, the famous white villages of the Cyclades or Andalusia.
“This is one of the solutions recommended today, because it allows responding to the effect of solar radiation on surfaces that will reflect this radiation instead of trapping heat,” Christine Leconte, president of the union’s National Council, told AFP. From architects.
She adds: “There is no single solution to reduce heat in the city.” “To respond to the impact of the heatwave on buildings, we must open up a range of solutions that adapt to different contexts, including heritage contexts.”
For housing, the most important measures are protecting windows from solar radiation… and rethinking urban planning on a broader scale by creating more green spaces in the city.
“We are not making the white roof a miracle solution, but we are starting to integrate it into our public policies,” says Margot Bellaire, assistant city planner at Grenoble (south-east) city council, a city run by environmentalists. This process, applied on the roof of an old factory that had been converted into a third space, reduced the temperature inside and around it.
“It should be part of a whole set of tools to modernize the city: greening, revitalizing the city on the ground with lighter covers, removing water leakage…,” adds the elected environmental activist.
The white roof solution is particularly popular in higher education buildings, says Arthur Gilardi, sales director at ARKsolutions, an SME in Toulouse, southwest France.
“We have people who need a break because they can no longer work in their warehouse and they don’t have an air conditioning system,” he says.
“The second reason is energy savings. Since you are cooling your building, you have less air conditioning, and we can talk about a 40% increase in air conditioning,” confirms Arthur Gilardi.
Working in large buildings also allows you to be more efficient, attests Julien Martin Kocher, Deputy General Manager of Cool Roof France, a pioneer in reflective painting.
“When I build 10,000 square metres, the equivalent of the Stadium of France, on a commercial rooftop, it will take me a week. If I do it on 100 houses of 100 square metres, it will take me three months.
Moreover, the roofs of tertiary buildings are often too weak to apply other solutions such as greening.
However, there are still doubts about the effectiveness of these paints that were developed for their refreshing effect, points out Stefan Hamori, Operations Manager of “Building Envelope” at the Center for Scientific and Technical Building (CSTB).
“This has not been fully proven today, with the expected scientific force,” he said.
“The benefit, if proven, would be greater for the residents of the upper floor. Hence the interest in using it instead for the roofs of wide and low logistics buildings.
There is also “the issue of the sustainability of these systems,” Mr. Hammouri continues. To maintain their ability, they must remain eggs.
He is also concerned that paints could have unwanted effects on the materials they cover. “Be aware of risks after the fact. We must rigorously evaluate these systems, something that is not being done today.
Finally, using white paint on facades or floors may be irritating to the eye because of its dazzling effects.
In Lyon, where the city tested the installation of a heat-resistant coating on pavement, the experiment will not be repeated, because “this product tested on public roads did not ultimately meet our needs and uses,” the community says.
However, she promised that “the use of white paint for facades and ceilings is one of the solutions that has been identified and will be part of a global action plan.”
