Yoann Richard
Ingénieur enveloppe du bâtiment, spécialiste carbone
Published on May 30, 2019

Reading time : 2 min

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Lycée Colbert in Lorient: successfully energy retrofitting a building in use

The Lycée Colbert general high school in Lorient was built using state-of-the-art 1950s and 60s materials and techniques: non-insulated pre-fabricated concrete façades, draughty single-framed glazing, etc. In 2014, Brittany Regional Council decided to give teaching blocks B and C a deep energy retrofit in the form of external thermal insulation and replacement window frames – while stipulating that classes would need to continue as normal! Egis rose to this challenge working together with Anthracite, a firm of architects.

An innovative technique

We designed insulated timber mounting frames for the new windows. These structures were pre-assembled and transported on-site where they were hoisted and then fixed one by one onto the façade...while students took their classes inside! The old windows – aside from their frames – were taken out and replaced with inside lining. Thanks to peerless time management, each classroom was only out of use for two days and the noisy business of fixing metal plates took place during the school holidays.

3 in 1 timber mounting frames!

The 150 timber mounting frames have three functions: insulating the outside walls, excluding outside draughts, and supporting high-performance joinery. Each mounting frame has two layers of glass wool insulation and an airtight rainscreen. They have a spruce frame and particleboard bracing.

Interior and exterior joinery comprises timber and black lacquered aluminium, respectively. South-facing windows have a solar factor of 0.40, meaning that they only let through 40% of heat radiation, while north-facing windows have clear glazing, i.e., a solar factor of 0.60. Both greatly reduce heat loss (Ug = 1.0 and 1.1 W/m²K). Once in place, the timber mounting frames are covered with metal cladding and slatted duckboard which limits the sun’s rays.

Lycée Colbert

- Crédits : Anthracite Architecture 2.0

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