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Published on October 16, 2020

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Lycée Bréquigny: a replicable, resilient and high-performance renovation model

The climate emergency is compelling us to act rapidly and massively to refurbish our physical assets. But how can you renovate a building whilst also guaranteeing liveability, health, energy efficiency and low carbon footprint? Such was the feat accomplished by Egis on an educational establishment: the Lycée Bréquigny in Rennes.

To refurbish the largest high school in Brittany (3,500 students), Egis designed a solution made up of innovative and ad hoc solutions based on the three criteria of sobriety, sustainability and effectiveness. This proposition took the form of a replicable renovation model and a unique design approach based on an iterative process conducted in permanent collaboration with all the partners involved. Aided by a digital model, the project was designed to meet exact needs and was improved continuously.

The energy renovation of Lycée Colbert in Lorient in 2015 had been a pilot experiment for Egis. The success of the Lycée Bréquigny project, which represents a step up in scale, offers proof of the pertinence of this model.

Bio-based materials and off-site prefabrication: low-carbon solutions

Egis focussed its design work specifically on achieving environmental excellence and leveraging the two main sources of greenhouse gas emissions: materials and transport. Consequently, the solution selected to reduce the environmental impact of construction work was to install wood framed walls and roofs made from wooden panels prefabricated locally (less than 50 km from the work site) and based on a tried and tested implementation process.

To guarantee teaching continuity during the work, the building procedure was carefully planned to keep disturbance to a minimum.

The use of off-site prefabrication therefore helped to reduce potential technical hitches, facilitate work on an occupied site, and control construction deadlines and quality.

A novel refurbishment model

In the space of 10 months, 10,000 m² of facilities on an occupied site were refurbished using a unique methodology that can be replicated on most educational facilities built more than 20 years ago. This model combines low-carbon renovation with the guarantee of liveability, user health and energy saving, with a seven-year commitment from Egis. A solution that rises to the challenges of the climate emergency, but also adapts to the financial constraints of local authorities.

For a given energy performance level, the average cost of this project only amounted to €725/m², as against €2100 for the construction of a new building. The carbon footprint of the construction products, meanwhile, is divided by 2.5, with emissions of approximately 400 kg CO2e/m² compared with 1,000 kg CO2e/m² generally observed in newbuild operations.


kWhpe/m²/year actual energy consumption


kg CO2e/m² FA of E3C2 carbon at equivalent newbuild standard


€/m² renovation cost

Egis won the "Construction and Fit-Out” category of the 2020 French National Engineering Awards (Grand Prix National de l’Ingénierie) for this novel operation  which showed that renovating a high school can have a less substantial impact on the environment than building a new, very low-carbon high school to equivalent energy efficiency standards. This model thus represents a viable response to the revitalisation of a resilient economy, with optimised and duplicable building and operation costs.

Partners: Région Bretagne, SemBreizh, Legendre Construction, Anthracite architecture, MANA, BEGC, JD EUROCONFORT, SPIE, Acoustb (Acoustique)

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