In the building sector, CO₂ emissions can be linked to three different stages in a building's life cycle: construction, use, and end-of-life demolition. Most emissions occur during the operating phase from sources such as heating, air conditioning and electrical appliances. Using a bioclimatic approach to rethink the design of new buildings, especially how they are insulated, is thus fundamental to improving their energy efficiency. The average energy consumption of a building in France is currently 400 kWhPE/sq m/year.

Under the Grenelle II Act, passed in October 2009 to implement Grenelle I, the energy consumption of new buildings must not exceed 50 kWhPE/sq m/year by 2012. Categorised as low-energy, these buildings are known as low-energy buildings (BBC – Bâtiments Basse Consommation) . Thermal regulations will also become more stringent so that all new and renovated buildings meet the new energy performance requirements.

In practice, that means constructing positive-energy buildings, which produce more energy than they consume. They cost more to build than conventional buildings, but the owner can pass on the excess cost to occupants, who will pay higher rents but save an equivalent amount on their energy costs.

Smaller-scale eco-variants can also generate substantial savings. For example, those proposed by Colas in 2010 represented a total reduction of 21,000 tonnes of CO₂ equivalent.
Bouygues Immobilier has come up with its own positive-energy building concept, Green Office^® in Meudon. On 11 January 2011, it teamed up with Alstom to create Embix, a joint company that offers energy management services for eco-communities.

The scope of the Grenelle Environmental Forum extends beyond the 300,000 housing units and 14 million sq metres of office space newly built each year: existing buildings will have to be made more energy-efficient too. The objective is ambitious: to cut consumption by 38% by 2020. A huge number of renovation projects are on the way, since the existing building stock comprises 30 million housing units and 814 million sq meters of office space (source: Ademe). To meet this challenge, Bouygues has put together several rehabilitation offers for different types of buildings and combined them with energy performance contracts.

Bouygues is constructing more and more buildings that qualify not only for energy-specific credentials such as the BBC low-energy building label, but also for broader certifications covering all environmental aspects of construction. These include the French HQE^® High Environmental Quality certification scheme, the North American standard LEED^® (Leadership in Energy and Environmental Design) and Britain's BREEAM^® (Building Research Establishment Environmental Assessment Method). By 2014 Challenger, Bouygues Construction's headquarters currently under renovation, will have all three of these certifications. Bouygues Construction also carried out the largest HQE^®-certified renovation project in France at the Tour First in Paris-La Défense.

(Updated: June 2011)