The building "is the worst sector" in its impact on the environment, taking into account its construction and its uses, believes Hélène Chartier, director of zero carbon urban development at C40, a network of global metropolises.
In France, it accounts for nearly 45% of final energy consumption and generates more than 25% of greenhouse gas emissions, recalls the Sustainable Real Estate Observatory (OID).
Its weight is even greater at the scale of cities alone. "It represents 50% on average of emissions, and that can go up to 70% in metropolises like New York", develops Ms. Chartier.
"The stakes are first colossal on the existing real estate stock", assures Walid Goudiard, director of the consultancy and project management assistance department at the JLL consultancy firm.
Smoothing the carbon footprint goes through the "reuse" of materials, especially during the renovation period, "more virtuous than recycling" he assures.
"Today, the (reuse) sector is losing money", in particular because the storage and logistics circuits are still in their infancy, but "when it will have reached a sufficient size, this will no longer be the case", according to him.
For example, "on a La Défense tower, we found that the heating and cooling networks were in good condition, we extended their lifespan, while we removed all the elevators, which were obsolete. is not a great backhand effect, but it's a global approach that we need to make more visible, "he describes.
"Feasible and already done"
The efforts are more quantifiable during the construction phase. "When we look at the life cycle of a building, carbon emissions peak during construction, then are smoothed out during use. Faced with an emergency, this is the best way to go quickly ", defends Ms. Chartier.
In France, construction represents 25% of the emissions emitted by a building over its entire life cycle, according to the OID.
In this area, "the least carbon-intensive material is the one that you don't need to put on", declared at the real estate fair Mipim Loïc Daniel, deputy managing director of corporate real estate for the developer Nexity .
Good construction also reduces emissions during the use phase. "We are able to create an office building that can practically do without heating, mechanical ventilation. It is feasible and has already been done", with a first construction out of the ground in Austria, underlined Mr. Daniel.
It remains to be developed on a larger scale. In front of French real estate players, the Minister for Housing, Emmanuelle Wargon, defended "demanding legislation" in the field of sustainable construction.
The ministry published during the summer the long awaited and many times postponed decrees for the ecological regulation (RE 2020) in the construction of housing. These new rules are applicable for building permits for residential use from January 1, 2022, before an extension of the buildings concerned, including offices, the following year.
Builders will therefore have to systematically calculate the environmental impacts of structures and check that they meet the objectives in terms of energy and environmental performance, sanitary quality or thermal comfort.
"In principle, the promoters were thinking about two dimensions: square meters and cost. We need to integrate a third, the carbon rating," says Mr. Goudiard.
Existing homes will also be affected by tightening regulations, with the ban on the rental of homes with the worst energy performance from 2028.