• Réseau de chaleur et de froid

The Château de Rezé heating network

Idex, awarded a 20-year heating network contract

Rezé’s urban land association (association foncière urbaine libre, AFUL) signed up to support plans to create a wood-fired heating network to serve the Rezé-Château district. This project was entrusted to Idex as part of a 20-year contract.



Our responsibilities span the entire length and breadth of the project:

  • funding the project,
  • designing and developing the energy production and distribution facilities,
  • building said facilities,
  • operating and providing upkeep and maintenance for all infrastructures, facilities, and installations, including the heating network and substations that serve the housing units.

The heating network upgrade and extension works have now been completed, and have extended the network from 1 km to close to 7 km in total.

How the wood-fired heating network works

Wood-fired heating networks come with a number of advantages:

- This is the only way of using low CO2-emitting renewable energy on a wide scale. It is a viable alternative to gas and electricity.

- By drawing on an alternative to fossil fuels, it allows us to adapt in line with energy market fluctuations.

- It contributes to creating jobs thanks to the steps involved in collecting, converting, and using wood fuel.

The heating network features a new boiler room primarily comprised of a 5 MW wood-burning boiler and two gas boilers with combined power of 13 MW.

The Château de Rezé district boiler room heat output is low-temperature, meaning water under 110°. It is distributed via a pre-lagged, pre-insulated steel heating network.

Cutting back on energy bills

In 2017, this boiler room supplied 14,550 MWh for the benefit of all users. 69% of all production drew on biomass energy in the form of wood chips and end-of-life wood sourced from within a 100 km radius. Idex undertakes to supply heating at a competitive price. In addition to wood energy fuel coming in cheaper than fossil fuel energy, subscribers benefit from discounted VAT rates.

Facts and figures

5 MW of wood-fuelled power

12,8 MW of gas-fuelled power

5,5 km of network line built

1 km of existing network line

32 substations, of which 22 were newly built

5 000 tonnes of wood used every year

80% biomass cover rate

3 000 tonnes of CO2 saved in 2017

6 000 tonnes of CO2 saved since the network was put into service