Heat wave: this real estate choice that many will regret not having made

June 2025 was the hottest June ever noted in France, after June 2003. And it is probably not over. A record to keep in mind as part of your real estate purchase project.

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Real estate prices that stagnate, credit rates fell around 3%… It is decided, you will take advantage of the long holidays to try toBuy the accommodation of your dreams ! Namely a top floor apartment, facing south, in a Haussmannian apartment. Finally, that was before the heat wave that has been hitting France for several days and the words, this Wednesday, July 2, of the Minister of Ecological Transition, Agnès Pannier-Runacher, according to whom “June 2025 became the second hottest month of June since the start of the measures in 1900, behind June 2003”.

There is no doubt that this sad record will be exceeded in the coming summer, with regard to the forecasts for meteorologists. What to transform your Haussmannian ideal into thermal butt! Too bad for the charm of the old, if you want to protect yourself against the multiplication of heat waves, it is better to buy a new accommodation. “”The new house is no longer content to be energy efficient in winter. It is now designed to also be a bulwark against summer heat, in a context where the rise in temperatures becomes a public health problem“Explains Loïc Vandromme, managing director of the manufacturer of Maisons Hexaom.

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Garage and cellar, natural thermal shields

Indeed, the Environmental regulations 2020 (RE2020), which new constructions have to respect since January 2022, has brought an innovation in size, with taking into account the summer thermal performance of housing. This is measured by the degree-hour (DH) indicator of discomfort, which aims to limit the number of hours where the interior temperature of the property exceeds 26 ° C, day and night. The maximum tolerated threshold is 1,250 DH per year.

To respect this limit, the RE2020 implies designing houses capable of staying cool without resorting to air conditioning, a large consumer of electricity and generating greenhouse gas emissions. A design that goes through the orientation of living parts to the southeast, in order to benefit from the morning sun while avoiding overheating in the afternoon. In the same vein, architects reduce the number of glass surfaces giving to the west as much as possible, where the sun sets. They also ensure the creation of kinds of Tampons areas Between the outside and the accommodation, such as garages or cellars, which serve as natural thermal shields.

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Thermal inertia materials

The design of new housing, as part of the RE2020, also gives pride of place to crossing ventilation, with a minimum of two opposite facades. Without forgetting theSystematic concealment of glass wallsby means of motorized roller shutters, whose opening and closing can be programmable depending on the sunshine schedules, aluminum adjustable sunshine, remotely adjustable, or even, for houses, pergolas.

Summer comfort also depends on the thermo-physical properties of building materials. Concrete and bricks are thermal inertia materials, capable of absorbing and slowly restoring heat, which “Allows to smooth temperature variations between day and night”underlines Hexaom. In terms of insulation against heat, wood wool and cellulose wadding are more efficient than conventional mineral wools, thanks to a Elev thermal phase shifté, from 10 to 12 hours. This corresponds to the discrepancy between the moment when the temperature increases outside and the moment when heat enters the accommodation. In summer, the sun begins to heat the houses at 10 a.m. With cellulose wadding, the heat begins to enter the house at only 5 p.m., when the external heat begins to decrease and it becomes possible to ventilate.