French 'Green Box on the roof ' innovation provides prefabricated low carbon building extension
French ‘Green Box on the roof ‘ innovation provides prefabricated low carbon building extension

French ‘Green Box on the roof ‘ innovation provides prefabricated low carbon building extension

Created: August 28, 2019. Updated: August 28, 2019.

An innovative office extension which adds a prefabricated low energy penthouse unit has been pioneered in France.

The result is a 945 m2 SDP timber framed terrace added to an occupied office building at an industrial park at Bron, near Lyon.

The rooftop unit has developed over 6 months off-site with wooden walls and joinery (reduced transportation).

It is designed for low carbon and energy consumption for regulatory purposes (23 Kw ef / m2.year final energy).

It incorporates innovative technologies of cooling and heating with motorized regulation, reducing the consumptions and the equipment in ceiling (common networks of blowing).

Materials are bio-sourced: floors, walls, roofing, insulation and joinery using 330m3 of wood and 325 m3 of hemp & flax of Biofib.

Recycled or recyclable materials are used for acoustic insulation, exterior terrace floors, tiling (recycling of production waste). And featuring the reuse of deconstruction materials in partnership with a local association (Mineka).

Climate resilience

The prefab extension is designed for resilience adapted to increase the frequency of heat waves (high thermal expansion of the walls 7 to 9 hours outside the glass walls, greening of the terraces, roofing and waterproofing adapted to the future installation of photovoltaic or solar thermal panels (overload and fixing). EPDM rubber sealing resistant to high thermal amplitudes.

Once in use, the extension offers comprehensive monitoring for user comfort and energy performance : continuous VOC measurement,, hygrometry, CO2 rate, all-purpose energy consumption and heating … with data display on workstations

A high priority is given to air quality through high performance air tightness and double flow ventilation with F7 filtration, non-emissive materials and all joinery with one opening leaf except 1 curtain wall.

The aim is to extend the building by adding a floor on the existing roof and on the occupied site and to build in less than 6 month with a dry (low carbon) solution in occupied site and without overloading the structures (lowering of limited loads) , creating healthy premises comfortable for future users.

The Green Box on the Roof project is a technical and architectural feature achieved in record time (6 months) with a high level of performance.

The building is in moderate seismic zone, which induces constraints in terms of structure and slab piercing. The wood frame construction is an asset for the reduction of overloads: the roof terrace is not a load carrier.

The exterior views are clear at all points of the offices. The large green terraces contribute to a feeling of well-being.

The new construction has a long facade facing east with a beautiful view of the Alps and a west facade overlooking a business park.

For the comfort of users, the use of insulation hemp & linen contributes to summer comfort (phase shift) and the natural regulation of hygrometry. The implementation of open wood joinery allows each user to ventilate his workspace naturally. Generous terraces accessible in reconstituted and vegetated wood will reduce summer overheating.

Photo credits: Alizée Pigeroulet, Studio Erick Saillet

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