From Paris to Toulouse, energy renovation work does not have the same impact on your home.

In Paris, a complete renovation can achieve class C, while in Bordeaux or Toulouse, the same intervention promotes an old house to class B.

For this study, three typical houses were examined: a first single-storey house with an upper floor of 120 m², a second, less compact single-storey house of 104 m², and a third, described as a "cube," with an upper floor on a slab foundation of 118 m². For each example, a comparison was made between two distinct geographical areas associated with different climates: temperate with oceanic influence in the North (Île-de-France, Hauts-de-France, Normandy) and oceanic in the Southwest (southern Nouvelle-Aquitaine, Occitanie).

Not all jobs are created equal.

Regardless of the type of house, the study reveals that not all renovations are created equal and that they do not all yield the same results in terms of energy savings. Small actions, such as insulating only the attic, can already reduce consumption by 15% to 22%. The savings are even greater when the walls are also insulated (between 12% and 28% savings). Finally, with a complete renovation, combining roof, walls, floors, and more efficient equipment, it is possible to achieve up to 78% savings on energy consumption.

Results that differ depending on the climate

When considering renovation work, it's important to keep in mind that the results vary depending on the region and climate. In Paris, many homes start with a very low energy rating (G or F). In this case, minor work on the attic or walls isn't enough to improve the energy performance certificate (EPC). In contrast, a complete renovation that combines insulation and modern equipment can achieve a C or even a B rating. With equivalent work, houses in cities like Toulouse or Bordeaux offer much faster improvements. It's possible to go directly from a G rating to a B rating.

According to Vincent Marcolla, product manager at ROCKWOOL: “Each dwelling must be studied on a case-by-case basis, taking into account its structure and climate. But one thing is certain: insulation remains the major lever for sustainably reducing energy bills, improving daily comfort and increasing the value of one's real estate.”