In January 2021, GRDF launched a call for projects for the implementation of efficient boilers for all collective housing renovation situations. After studying the submissions received, the panel chose the concept proposed by Christian Cardonnel Consultant, who teamed up with Vergne Technologies and Anjos Ventilation to present a response.

A clover of four ‘THPE’ (very high energy efficiency) boilers 

It’s a ‘four-leaf clover’ concept that would allow several boilers to be connected to the same flue, with a new design and layout. Hypermodulating condensing boilers (from 1 to 30 kW), well suited to the heating and DHW needs of flats, combined with humidity-controlled ventilation for improved air quality. This concept could halve the energy consumption of each residential unit, offering really significant savings,” explains Christian Cardonnel. There is a lot at stake, with a high-performance renovation solution on offer to around 710,000 homes connected to a gas-fired CMV system. 

Aim: on the market within a year

The solution will be developed and tested with a view to obtaining technical approval and launching the market introduction in late 2021 or early 2022. Christian Cardonnel and his partners will refine the designs and propose an operational prototype to be tested using an experimental tower. Following on from the call for projects, a partnership with GRDF is now envisaged, to support these next steps in the following months.

This renovation solution for gas-fired CMV systems by adapting the flue through which the combustion products are evacuated will be aimed at subsidised public housing and social developers as well as private co-ownerships. By providing access to the energy performance of a condensing boiler, it will allow the owners of this housing built in the 1980s to benefit from energy saving certificates and greater comfort.


“I am honoured to have been selected at the end of this consultation. We must continue to design new gas solutions, particularly for existing homes. There is a future for gas in the building sector, especially with the development of green gases, which emit 90% less CO2 than natural gas. And we can’t repeat this often enough: France will not be able to satisfy all of its energy needs with electricity alone! “