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E2REBUILD Site Voiron

Country & City

  • France
  • Voiron


Contact Information

The Voiron demonstration site of E2REBUILD project is a multi-storey building in the department of Isère. The building was made of concrete with no insulation, it had natural ventilation and the windows were first-generation PVC double-glazing 4-6-4. All dwellings had an individual gas boiler for domestic hot water production, but each dwelling had its own different heat production – either electric heaters (ca. 29 dwellings with an energy demand of 529 kWh/m² year) or fossil fuel boilers (c. 43 dwellings with an energy demand of 202 kWh/m² year). The building’s average consumption was 265 kWh/m²/yr.

The retrofitting programme reduced the energy consumption to 95 kWh/m²/yr and created a structured heat and domestic hot water production through a collective heating system (gas boiler) and solar thermal panels for hot water. Mechanical ventilation was installed and the roof, floor and walls were insulated. Furthermore, balconies were closed using prefabricated elements.

*The KPIs for the new building are compared with the baseline of a reference building.

The demonstration site in Voiron consists of an overall gross floor area of 3646 m2 that has been refurbished in the project. As a result of the energy efficiency, the space heating was reduced from 210 kWh/m²/yr (business as usual) to 59 kWh/m²/yr, while the consumption for domestic hot water was reduced from 48 kWh/m²/yr (business as ususal) to 32 kWh/m²/yr. Together with electricity, the total consumption went from 265 kWh/m²/yr to 95 kWh/m²/yr, representing a decrease of more than half in comparison to the reference building.

This represents 594 MWh/yr of final energy savings. According to the primary energy and CO2 factors provided by the project, the primary energy savings rises to 1020 MWh/yr while the CO2 reduction amounts to 127 tonnes every year.

Regulatory & Administrative

Regulatory & Administrative
Encountered barriers

Difficulties were encountered when implementing prefabrication: unfavourable regulations, as well as problems discovered on-site (e.g. need for reinforcement of the balconies).

A better preparation during the design phase was necessary, possibly using business information modelling as in some other demonstration projects. In Voiron, the use of prefabrication was too limited and the site didn’t fully benefit from its added values.


Encountered barriers

The implementation process was slowed down by the tenants.

The subsequent involvement of the tenants during the implementation process, as well as the participation of different stakeholders, ensured a well-accepted and smooth project, even though sometimes tenants experienced disturbances.


The refurbishment measures implemented in Voiron included:

Energy efficiency in buildings

  • Retrofitting the building envelope
    • Insulation of the whole building envelope
    • Closing of balconies using prefabricated elements
    • Reduction of thermal bridges
  • Building services (HVAC and lighting)
    • Highly efficient centralised heating system
    • Renewal of the electrical system
    • Heat recovery in ventilation system

Energy systems integration

  • Thermal collectors
    • Production of domestic hot water

The investment cost for the intervention was EUR 869/m², which amounts to EUR 3.2 m in total. According to the provided data, the annual cost savings for energy result in EUR 116 070 for monitored values. The results show that the payback period according to the data provided and SCIS calculations is 28 years.

SRT data