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Prefabricated renovation with BERTIM technologies: "L'étape" building in La-Charité-sur-Loire

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The building "L'Etape" was built in the early 1960s in the city of Charity sur Loire. It is a social housing building and the renovation aims to create spaces for temporary houses, training and short-term activities organized by the municipality.


The existing building presents a rectangular form on 4 levels and a total floor area of around 502m².


The general level of conservation of the building is quite poor as well as the energy performances: the external walls are made of blocks masonry, with two rows of load-bearing walls, the floor are made of joists, hollow concrete slabs and concrete slabs. The roof is uninsulated and flat, while the windows present single-glazing and wooden frame. The measured average thermal transmittance of the envelope accounts for 2.5 W/(m2 K). Concerning the systems, the existing building has is connected to the district heating, and there are radiators installed in the apartments.


The first step for a prefabricated renovation consists in a detailed survey and measurement of the building façade, and in this case 3D scanner, photogrammetry with drone and total station method have been applied. The building consumption accounts for 200 kWh/m2 per year, corresponding to a class D according to French regulation RT2012. The renovation has been focused on the insulation of the envelope through a prefabricated façade element. The intervention had been designed according to cost-optimal approach, after the evaluation of different variants and levels of insulation of the façade.


The key technology adopted is a 30-cm thick prefabricated wooden façade with around 25 cm of insulation (15 cm of glass wool + 10 cm of polyster). The overall performances of the renovated building are estimated to be lower than 85 kWh/m2,.


The façade has been following the industrial LEAN MANUFACTURING process (Operational Excellence). Within the factory, the production management system is modeled on that of the automotive industry, based on three fundamental elements: the reduction of costs by the elimination of wastes, the pro -duction in just in time, the quality. Thanks to the adopted process, the production of the modules for the renovation took only 10 days.


The number of walls planned for the renovation of the "L'étape" building is 15 prefabricated panels in the factory on 284m² and a site adaptation of 118m2. Windows are already integrated into factory walls, as well as exterior cladding and the overall mounting process lasts for 5 days, with the activity of three workers and one crane operator.


This case study represents an example of how prefabrication can speed-up the renovation process significantly improving the building performances and aesthetic.


For more information on the renovation of l'étape building check the BERTIM website.

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