Renovation of Lycée Bréquigny

The energy renovation of teaching buildings, that created a big impact in efficiency and heating needs, avoided reconstruction and delivered remarkable carbon savings.

Built at the end of the 1950s, Brittany’s largest high school was a particularly wasteful energy consumer: its renovation had become essential in order to provide students and teachers with comfortable and welcoming premises.

This ambitious €20 million project set out to make the buildings just as energy-efficient as new-build constructions. 7,500m² of facades were re-clad with wood frame walls in a record-breaking seven months, on a construction site still occupied by more than 3,500 people.

This was made possible by combining off-site construction, bio-based materials, energy calculations, consultations with occupants and consumption monitoring.

Sustainable measures
This project offers a response to the major challenges faced by construction and to global carbon neutrality: reducing consumption of raw materials, lower energy consumption, controlled performances and carbon sequestration.

By avoiding the demolition and reconstruction of the building, the need for primary materials such as concrete or steel was substantially reduced. Renovating existing constructions is naturally economical on raw materials and provides an initial response to resource scarcity.

The built structure was made more resilient and durable, and the work on these buildings provided the opportunity to considerably reduce energy consumption. The addition of wall and roof insulation in large quantities helped cut heating needs considerably.

The renovation of ventilation systems combined with the improvement of airtightness were also key factors in reducing heat loss in the buildings.

The addition of finely calibrated solar protection helped to guarantee user comfort even in the event of very hot weather, whilst maximising natural light. Finally, all the lights were replaced so as to reduce electricity consumption from lighting the premises, a major cost in tertiary buildings.

The quality of indoor air is a big feature of the operation, with the carbon dioxide concentration on the premises reduced to 1,300 ppm for a 15-minute period. The outbreak of the Covid-19 pandemic reminded people of the importance of air quality and ventilation as components for retrofitting buildings.

By using bio-based materials for the works, in particular wood for the isolating external walls, the environmental impact of the project was further reduced. A life cycle analysis demonstrates that the project’s carbon footprint of 400kg CO2 eq/m²) is two and a half times lower than for the new-build construction of a high school, even with alternative and low carbon construction methods.