Roof renovation proves its efficiency in the energy performance of individual houses

The study puts the energy renovation of roofs back at the top of the priorities to reduce the energy bill of the French and remove more than 1 million individual houses from the status of energy sieves.

A priority: improving the energy performance of our homes

Housing represents almost a third of energy consumption in France and 25 to 30% of energy loss from buildings passes through the roof. Added to this is growing energy poverty for more than 6 million households.

At a time when the State and communities want to accelerate the energy renovation of our homes, the PROMOTOIT association, which brings together seven companies specializing in the manufacture of construction materials for roofing, wanted to quantify the potential for energy savings. energy associated with the renovation of roofs of individual houses. She entrusted this study to the firm TBC Innovations which worked on the basis of a representative sample of the stock of houses built before the year 2000 (i.e. 75% of the energy consumption of the stock). The study distinguishes four typologies of houses: the most important concerns houses with converted attics (33% of the stock), followed by houses with convertible attics and unused attics (31% for each of these two typologies) and houses with roofs. dishes (5%).

Energy savings: up to nearly 40% heating savings per m2 of living space during a roof renovation with fitting out and efficient insulation of the attic

At the scale of a house, the energy renovation of the roof is a priority because it allows significant energy savings. Thus, heating savings per m2 of living space vary from 24% to 29% for houses with already fitted attics and from 28% to 39% during a renovation with attic conversion. The potential for gains is then higher due to the surface area created and the better compactness of the building after development.

Houses with converted attics: almost 30% are energy sieves with poorly insulated roofs

The study shows that insulating the roofs of houses with converted attics is a priority. In fact, 59% of them have very insufficient insulation, and 29,5% are considered energy sieves (classes F and G).

Insulating the 2,6 million most energy-intensive converted attic houses would represent a potential saving of 23,4 TWH over 10 years, or the equivalent of the production of 4 nuclear reactors (of 6 TWh) or the annual electricity consumption over a decade of three metropolises such as Lyon, Toulouse and Strasbourg.

The double advantage of attic conversion: energy savings and creation of 15 million m2 of living space

Nearly one in four convertible attic homes has very insufficient insulation and 14,5% are classified as energy drains. The development and energy renovation of their attics would provide potential energy savings of 16,7 KWhep/m²/year, coupled with the creation of 15 million m2 of living space. With the Climate and Resilience Law which fights against the artificialization of land, these m2 available thanks to the development of the attic are a resource to be exploited.

For André Dot, President of PROMOTOIT: “Renovation of buildings in general, and roof insulation in particular, is essential to sustainably reduce energy consumption. Among the most energy-intensive roofs are those of around 30% of houses with converted attics, today in the status of thermal sieves. It is urgent to encourage their energy renovation to combat the precariousness of their inhabitants. »

Thermal strainers: removing more than 1 million houses from this status by renovating the roof

In conclusion, the study shows that after efficient roof insulation, more than 60% of renovated houses, or more than 1 million houses, would exit the status of energy sieves (criteria G and F according to the DPE classification).

More precisely, the following would emerge from the status of energy sieves after efficient insulation of the roof:

• 63% of houses with converted attics, or around 821.000 houses;
• 66% of houses with convertible attics, or around 244.000 houses.

Methodology :

The study entrusted to the TBC Innovations firm focuses on the energy gains of efficient roof insulation. It took place in three stages:

• Step 1: Characterization of the stock of individual houses (attic typologies, insulation levels).
• Step 2: Estimation of energy gains at the scale of typical individual houses to be renovated (converted and converted attics) with assessment of the impact on the DPE classification.
• Step 3: Extrapolation to the national park level (according to climatic zone, heating energy, type of attic, level of insulation).

Illustrative image of the article via Depositphotos.com.