Energy renovation: how condominiums can increase their DPE rating thanks to insulation

Before changing their heating system, it is in the interest of co-owners to insulate their walls and floors. The energy consumption of certain housing known as “thermal sieves” can thus decrease by more than 50%, and the DPE rating improve by three notches.

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When it comes to energy renovation, there is one type of work that must precede all others: thermal insulation of the home. “It constitutes the starting point of any energy saving approach”explains the co-ownership trustee Cotoit, a subsidiary of Crédit agricole Immobilier. However, in recent years, the government has placed a lot of emphasis on the installation of heat pumps. “It doesn’t make senseestimates Vincent Marcola, product manager at Rockwool, a company specializing in home insulation with rock wool. Replacing your heating system before insulating is the best way to make a mistake when sizing your heat pump.. The power of the latter depends in fact on the energy consumption of the home, which will decrease significantly after insulation. The individual therefore risks opting for a heat pump that is too powerful and consumes electricity.

Rockwool therefore pleads for his parish: it is necessary above all to insulate the accommodation, with rock wool (molten basalt), or glass. In the case of a detached house, the attic – whether lost or converted into a masculine space, right?:) – can be renovated “quickly and easily”all without having to leave the accommodation for the duration of the work. “This is one of the most requested renovation positions”explains Vincent Marcola. And for good reason: around 30% of heat loss from a house comes from the roof.

In the case of co-ownerships, things are slightly more complicated since the work must be voted on in a general meeting by a majority. If this is the case, insulating the walls from the outside represents the best investment, but can be accompanied by that of the roof or low floors to maximize the results, and improve the energy performance diagnosis of the condominium as much as possible. , and the housing there.

Walls, priority for co-owners

This is demonstrated by the case studies carried out by Rockwool. Several Parisian apartments of 85 square meters were taken as a model. They are the archetype of a thermal sieve, namely goods with a DPE G and whose heat loss is maximum. Their water heater and heating run on electricity. “Paris, like many other large European cities, has an old building stock where buildings were often constructed before energy efficiency standards became a priority. These homes, sometimes built with massive but uninsulated walls, are particularly exposed to thermal losses.explains Rockwool.

>> Our service – Energy renovation: calculate the amount of your aid (MaPrimeRénov’, CEE, etc.) and find the right craftsman for your work

Depending on the position of the apartment in the building, the work to be considered differs. The intermediate floors benefit from the best scenario. The apartments on the lower and upper floors allow you to “steal calories”, that is, to take advantage of other people’s heating to maintain a comfortable temperature in your home. They generally have only one facade facing the outside, minimizing heat loss. The DPE of this type of apartment is therefore far from being catastrophic, since it reaches the letter E. In this case, insulation of the walls, from the outside or the inside, would make it possible to reduce the energy consumption of the household by almost 50%, going from 250 kilowatt hours per square meter per year to only 130. The DPE would thus go from E to C, or two letters gained.

The top floor, the worst off

But for an identical accommodation, this time located on the ground floor, the initial observation is more severe. He only benefits from the heating of his neighbor above, and is penalized by the loss of heat from the parking lot located on the lower floor. Its energy consumption is approximately 75% higher than that of an intermediate floor, and the insulation of the exterior walls would only provide 27% energy savings this time. To maximize results, it would be appropriate to also insulate the floor, recommends Rockwool. This would make it possible to more than halve its energy consumption, and obtain a D grade, very close to C.

Third and final scenario: an apartment, still identical, this time located on the top floor. “It’s the most penalized housing”explains Rockwool. Located at a corner, it is generally in contact with several exterior facades. Its energy consumption amounts to 661 kilowatt hours per square meter per year, almost two and a half times more than the same apartment located on an intermediate floor. In addition to the walls, it is therefore appropriate for this owner to insulate his floor. Such a project would allow it to obtain the greatest energy savings: 57%. The DPE label would change completely, from F (thermal strainer) to E.