With climate change and the increasingly frequent, long and intense heat waves it causes, insulating buildings against heat is a new challenge in construction or renovation.
How do you protect a building against heat?
There are two levers for action: “Protect yourself against solar radiation and let the heat out”, says Karine Jan, head of the Sustainable Building department at Cerema (Center for studies and expertise on risks, environment, mobility and planning).
For the second part, the most effective solution is the most obvious: airing at night. But it is from the design stage that this can be facilitated, with so-called continuous buildings, that is, open on at least two facades, which allow the creation of airflows.
Inside, the ceiling fans, already very present in ortre-sea, should also become more common, prediction Karine Jan† To reduce exposure it is necessary to “limit large glass areas open to the south”explains Loïs Moulas, General Director of the Observatory for Sustainable Real Estate, “Introduce niches, terraces, to ensure that there are shaded areas”†
You can also add ‘umbrellas’ to the windows, wooden slats oriented so that they let in light in the winter when the sun is low, but not in the summer when it is high in the sky.
And, of course, the installation of shutters that allow you to cool down without being in the dark, as there are already in the South (key chains, Nice shutters, etc.).
The main aim is to avoid the installation of air conditioners, which exacerbate global warming and, in a vicious circle, increase the need to use them, underlines Loïs Moulas.
Which materials are most effective?
The heaviest building materials, such as sawn stone or concrete, are the most insulating. On the other hand, they are also expensive and polluting.
They are therefore in violation of the 2020 environmental regulation (RE2020), which has been in effect since January 1. To limit greenhouse gas emissions from new construction, it prefers so-called biosourced materials (of natural origin), such as wood.
But with biosourced materials we can combine effective insulators, such as concrete with wood… or biosourced insulators that are also just as effective, such as hemp or wood wool, or cellulose wadding, says Karine Jan.
What is the State doing to adapt buildings?
The RE2020 makes summer comfort, or protection against heat, an essential criterion for new construction. The indicator to measure it is called the degree of discomfort. When the architect designs a building, the number of hours in the year (including heat waves) is calculated when the indoor temperature should theoretically exceed a certain threshold, usually 26 degrees.
Every hour this threshold is crossed, one degree more represents a point of discomfort. And in a year, the building cannot hold more than 1,250. After 350 degrees of inconvenience, a building can be authorized, but it will be considered more energy consuming as the residents are more likely to install an air conditioner there.
To calculate it, we take into account a multitude of criteria, explains Marc Schoeffter, engineer in the construction department of Ademe (Agency for Environment and Energy Management).
“The summer comfort will be taken into account in relation to the size of the building, the size of the openings, the shading that we can put there, the inertia… a building with a high inertia will be able to dampen the solar wave during the day and restore the stored energy during the night”.
The Energy Performance Diagnosis (DPE), mandatory for the sale or rental of a home, also takes into account parameters of summer comfort: insulation, presence or absence of shutters, possibility of creating drafts, etc.
(AFP)