In Dijon (France), with the support of ADEME, Elithis has designed a circular, low-energy consumption tower. The aim was to achieve a positive energy building through the eco-citizen conduct of its occupants.

The selection of the tower’s position was not left to chance. “We studied everything in detail to ensure nature was on our side: the site’s orientation, masking by the neighbouring buildings, dominant wind patterns, etc.”, explains Thierry Bièvre, general manager of Elithis, an engineering firm specialised in energy efficiency. The company needed 2,000 sqm of new premises that had to be exemplary in terms of sustainable development, so it finally built a tower with a surface of 5,000 sqm that will be open to other tenants.
The first feature is the tower’s compact, ovoid shape. “This reduces the facade surface area by 21% compared with a conventionally shaped building, and so limits climatic impact. In this way, it was possible to incorporate large glazed surface areas without compromising the building’s thermal performance”, explains Lionel Combet, engineer with the Burgundy regional Office of ADEME. Three quarters of the facades are glazed to allow in as much light as possible and limit the need for artificial lighting. Another innovation is the “solar shield”, in the form of red expanded metal mesh, fitted to the building’s most exposed surfaces. This “solar protection” prevents the building from overheating in summer while retaining excellent transparency. Inside, artificial lighting is triggered by the presence of occupants and the level is adjusted to factor in the intensity of the natural light.

Consumption of a 250 sqm home
A 100 kW wood-fired boiler supplies the heating. Barely 8 cu. m. of wood pellets will be used each year, that is, the equivalent consumption for a 250 sqm dwelling. Finally, 560 sqm of photovoltaic panels installed on the roof will generate 50 kWh of primary energy per square metre (kWhpe/m²) per year. The tower’s annual energy requirement is estimated at 70 kWhpe/m², so just 20 kWhpe/m² needs to be found. “This is not yet a positive energy building, but we have laid down the gauntlet to achieve that goal and all users have been made aware of the eco-behaviour they need to adopt.” Today, the main use is for offices. Each new owner or tenant must sign an eco-behaviour charter. Thereafter, a steering committee has been tasked with organising meetings to make sure these issues remain top-of-mind for all the building’s occupants.