Case Study: nZEC - New construction of 32 dwellings in the EcoDistrict De Bonne, Grenoble, France

Short Description

Located in a new suburb, De Bonne, which had ambitious objectives in terms of energy (this suburb was associated to the European project Concerto Sesac), the objectives for the construction of Le Partisan were in line with the global objectives of the suburb.

Key Elements

Certification

The following certificates were obtained for this project:

BBC effinergie: Certificate obtained for consumptions of primary energy lower than 50kWh/m².year for heating, adjusted according to the climatic conditions and altitude.

Qualitel Habitat&Environnement by Cerqual: This certificate is related to the compliance with some commitments:

• Energy performances
• Water and Electricity savings
• Environmental management of the project
• Cleaned building site
• Choice of materials

QEB: Management of the project respecting the environmental quality of buildings

Thermal Insulation

Among the key elements of the project, the work on thermal bridges thanks to the choice of an external insulation (20cm of polystyrene) is crucial. Moreover, the insulation from the outside is coupled with the use of green roofs and the installation of double-glazed windows to reach a good level of insulation. The performance of the insulation was checked through thermographies.

Air Tightness

Specific clauses related to airtightness had been introduced in the contract submitted to the building companies. These companies were alerted and informed about the new methods to use. Moreover, tests were carried out to check the air tightness of the building which appeared to be excellent.


 

Ventilation

In terms of ventilation, it was chosen to install a mechanical ventilation with heat recovery. Indeed, the conception team decided that, at that moment, mechanical ventilation without heat recovery was not a good choice because of low yields, high costs and problems of maintenance.

Solar Thermal

A solar domestic hot water system was installed on the roof (32m² of solar panels) and followed by Actis. The remaining needs in terms of domestic hot water as well as the heating needs are ensured by the district heating network.

Main Results

• First of all, a thermal dynamic simulation was carried out in advance to optimize the choices made in terms of conception.
• The insulation from the outside coupled with the use of green roofs and the installation of double-glazed windows enabled to reach a good level of insulation.
• This level of performance as well as the performances of the technical installations was monitored thanks to instrumentation set up at the building and the dwelling level.
• The heating depends on the district heating and the domestic hot water is partly produced by solar thermal panels. In order to use natural lighting to the maximum, the ratio between the windows’ surface and the living area is close to an average of 21%.
• In terms of delays, the decision, made during the conception phase, to aim the BBC Effinergie level did not provoke retardedness.
  
  
  

Lessons learned

• Among the strong points, it has to be underlined that specific clauses related to airtightness and the energy level to reach had been introduced in the contract submitted to the building companies.
• These companies were alerted and informed about the new methods to use. In terms of technical choices, the use of sun breakers (to maintain a good comfort in summer), of a mechanical ventilation without heat recovery, of a solar system for the production of domestic hot water and the use of water savings products were strong points.
• Moreover, the awareness campaign dedicated to inhabitants as well as the monitoring of the building and the analysis of consumptions during 2 years enabled to ensure a good working and a good use of the building.
• Among the weak points, it can be underlined that the airtightness tests were not controlled by the contracting authority. Moreover, due to the start-up of the building, the results of the first year, in terms of consumptions, were above the expectations.
  
  
  

Additional Information

Ms Carine Puyol
USH - The French Federation of Social Housing Providers
E-mail: carine.puyol@union-habitat.org
Web: www.union-habitat.org