Blocks 24 and 25 in Lyon-La Duchère - Durable insulated concrete housing for long-term performance

68 social housing units in Lyon-La Duchère, France, designed by Philippe Dubus Architectes for SACVL – completed in 2021

Project overview

Key project data

Architectural design and construction using the GBE System

What urban, architectural and energy-performance requirements did the façades need to address?

Blocks 24 and 25 had to address several requirements specific to social housing: providing a high-performance and durable building envelope, controlling long-term operating costs and integrating buildings of different sizes into a sloping site between the La Duchère plateau and Parc du Vallon. Philippe Dubus Architectes developed a common mineral architectural language while differentiating the building volumes through variations in concrete colour. The façades constructed using the GBE System incorporate 14 cm of polyurethane insulation with a declared thermal resistance of R = 6.36 m²·K/W. Continuity of the insulation helps reduce heating demand, while the internal concrete leaf, located within the insulated envelope, provides thermal mass and contributes to summer comfort. The loggias represented an important junction condition: their specific design had to maintain continuity of the thermal insulation while enabling the structural support of the external slabs.

Why was the GBE System suited to this project?

The GBE System was suited to the development because it combines load-bearing structure, thermal insulation and the final external architectural finish within a single cast-in-place concrete wall. The system is not prefabricated: the two concrete leaves are cast simultaneously on either side of the insulation using conventional formwork construction methods. This approach retains the architectural flexibility of cast-in-place concrete and avoids the repeated joints associated with prefabricated panel construction. The light grey, dark grey and yellow-beige tones are achieved through pigments incorporated directly into the concrete, without an additional coloured surface finish. At the loggias, the external concrete leaf increases locally from 10 to 15 cm so that it can contribute to the structural solution while retaining the full 14 cm insulation thickness. The GBE System therefore allows the wall build-up to be locally adapted while maintaining the overall principle of a continuous, insulated and cast-in-place building envelope.

What benefits does this project demonstrate?

Blocks 24 and 25 demonstrate the relevance of the GBE System for a housing provider responsible for buildings over the long term. The 14 cm polyurethane insulation, with a declared thermal resistance of R = 6.36 m²·K/W, contributes to reducing heating demand, while the thermal mass of the internal concrete leaf contributes to summer comfort. The insulation is protected between two concrete leaves and the external architectural finish is obtained directly from the formwork, without stain, paint or render used to provide its colour. This simplicity reduces the number of applied layers requiring future maintenance and supports a whole-life cost approach. The construction process also retains a conventional daily cycle of formwork, concrete placement and formwork removal; an experienced site team achieved approximately 30 m² of wall per day. Once stripped, the wall is already load-bearing, insulated and externally finished, reducing subsequent finishing operations. The housing development also achieved the Effinergie Plus label.

Project awards and recognition

The Effinergie Plus label applies to the housing development. The ÉcoQuartier Level 4 label applies to the wider La Duchère urban development and not specifically to Blocks 24 and 25 or to the GBE System.