A sustainable office building with a steel structure: The 255

The 2009 winner of the competition for the design of a positive energy building promoted by Regional Council of Bourgogne, France aims to be the best performance building in the tertiary sector in this region. It was built with a steel structure and composite flooring supplied by ArcelorMittal Distribution Solutions.

Detailed information

Located in the new business park Parc Valmy, north of Dijon, the 3400 m2 '255' office building is characterised by its low energy consumption. This was achieved thanks to the choice of construction materials, the implementation of standard construction technologies, and the emphasis on a structure with high inertia, the external insulation or the treatment of thermal bridges.

The installations of more than 450 m2 of photovoltaic panels on the whole roof converts the building 255 into a 'positive energy building' with an energy overproduction of 20 000 kWh/year.

However, this building with its unique concept will not be an exception. Although it is a technically highly accomplished building, the 255 is a model that can easily be reproduced with a cost similar to a more classical construction and with lower operational costs in the long run. 

SETUREC and the other companies that occupy this building participate in the reduction of energy consumption in the tertiary sector and are therefore taking a 12-year step ahead of the legal obligations established in Grenelle II. The objective of the French regulation Grenelle Environment I and II is to encourage and promote economical urbanism as far as space and energy resources are concerned. It requires that starting from 2012 every new building in France must be classified as a low energy consumption building (with a maximum consumption of 50 kWh/m2). From 2020 on, every new construction must have a positive energy balance.

255: A low energy consumption, passive, or even positive building?

Theoretically, the 255 building fulfils the criteria of a positive energy building. Thanks to its photovoltaic installation and the wind turbine, which was designed by french designer Philippe Starck, the building will produce 12% more energy annually than it actually consumes. A series of qualitative measurements will be applied in order to evaluate the real energy consumption and, in case it is necessary, certain parameters will be adapted in order to maintain the classification of a true positive energy building.

Technical principles of the construction of 255

- A strong inertia: The aim is to store the heat or cold air thanks to the building's mass (flooring, walls, etc.).
- Handling of thermal bridges: Minimisation of the heat leaks due to defects in thermal resistance in the assembly of two different insulation materials.
- Air tightness is a vital condition of a passive building, and the aim is to create a completely hermetic building.
- Heating with wood pellets, ventilation system with double flow, and hydraulic wells among other measures assure the maintenance of temperature inside the building in winter and cooling in summer
- Lightning and comfort equipment: A lighting system based on movement detectors variable in function as per the intensity of natural light, sunshades, rainwater recovery for the sanitary installation, free-cooling, etc.

Why 255?

As the story goes, the numbers appeared to the architect by chance at the time of the conception of the building. Finally, when the simple sketch was further elaborated in the design phase, the three numbers became visible to everyone in the three white oriels that somehow overhang and stand out against the red brick facade.

Its destiny was definitely sealed when the construction permit was received and the building had to be provided with an official name. 

Large spaces, lights, big windows, and glass floor boards let light and warmth inside the building, the kitchen is overlooking a patio, the facade consists of warm colours -- the 255 was certainly conceived as a space with modest energy consumption, but nevertheless it is a modern, comfortable, and welcoming building.

The global approach not only contains the building itself, but it is also aimed at its occupants and an increase in their awareness of the environmental issues and energy saving. They are invited to use public transport as Parc Valmy was connected to the tram system in December 2012.

Project information

  • Dijon
  • France
  • Architect:
    Cédric Vernay
  • 2009 - 2011
  • Engineering firm:
    Seturec Engineering
  • Photographer: 
  • Text:
    Seturec & Constructalia

Technical details