Energy-Efficiency Before the Summit
The work on Europe's highest construction site is almost finished: with the last shelter before the summit of the Mont Blanc, the 'Refuge du Goûter', the French Alpine Club will have a building that is almost completely self-sufficient with regard to energy and water.
Architects: Groupe H, Paris
Almost 30,000 alpinists attempt to climb the Mont Blanc every year and records show that about a quarter of these stop over at the Refuge du Goûter. The French Alpine Club's mountain hut is situated over 3,800 metres above sea level, at an altitude of approximately 1,000 metres – corresponding to about five hours by foot – below the highest mountain peak in Western Europe.
The previous building, dating back to the 60s, had become much too small for the growing number of visitors. On top of that, it consumed enormous amounts of energy. The construction workers of the new Réfuge were among the last guests of the old hut, which will be completely torn down in 2013. Only a slightly newer annex will remain as an emergency shelter in winter.
The new mountain hut, designed by the Swiss architect Hervé Dessimoz and his Paris office Groupe H, will provide modern accommodation for 120 guests on four floors – but only in summer. It is however almost completely self-sufficient as far as energy and water requirements are concerned. Another outstanding feature is the construction itself, which serves as a model for building in extreme locations and illustrates how resources can be saved by means of intelligent lightweight construction.
Silver egg above sheer cliff
Hervé Dessimoz and the wood construction engineer Thomas Büchi had already cooperated in the design of the Palais de l’Equilibre for the Swiss National Exhibition 'Expo 02' in Neuchâtel in 2002. Since 2004, the iconic globe made entirely of wood is located on the CERN grounds in Geneva. For the Mont Blanc project, they chose a similar shape and construction using glued laminated timber, but opted for a completely different envelope. Stainless steel sheets, photovoltaic elements, solar thermal panels and a total of 55 roof windows are distributed over the outer skin of the oval structure.
The segments of the prefabricated lightweight wood construction making up the building envelope were transported to the site by helicopter. The maximum carrying capacity of the helicopter of about 500 kilogrammes was therefore an important design and construction determining factor. Achieving maximum energy efficiency was not restricted to operational aspects of the mountain hut: the 'grey energy' (including energy used for transportation) used for construction and later disassembly was also kept to a minimum.
How the wood construction engineers set about achieving this is illustrated by the support structure: the building used a total of about 150 tonnes of wood, 30% of which were obtained from nearby forests around Saint-Gervais, 60% from the Departement Haute-Savoie and only 10% from Burgundy. To minimise the thickness of the support structure, all the cut trees were examined by ultrasound and scanner and only the most regular ones were selected for the building. A material saving of up to 60% was made by using glued laminated wood beams instead of standard timber beams.
To be able to mount the individual elements without a helicopter, a crane was set up at this extraordinarily high altitude. The construction workers nevertheless had a tough job – not least due to the lack of oxygen in such regions. Building work was limited to five or six months in summer, which stretched the construction phase to over two years.
Self-sufficient except for cooking gas
The (almost) energy-neutral operation of the building is based on good insulation, which also made use of wood fibre materials. Triple-glazed windows were fitted with an additional 8-millimetre thick glass pane to provide extra protection from the harsh weather conditions. The outer wall elements were delivered with only the frames of the windows fitted, while the glass packages arrived separately. These were stored for a period of one week to allow the glass to 'acclimatise' to the low air pressure at this extreme altitude, before they were fitted in the building envelope.
The thermal energy used in the mountain hut is mainly obtained from the sun via solar energy panels (54 m2) integrated in the building shell. A combined heat and power unit run on rapeseed oil (and a little diesel) is available to cope with peak loads. The drinking water supply system also relies on solar energy. A snow melting system, operating on solar thermal energy, is located behind the house and melts snow as long as the sun shines. The water obtained is fed to the building by means of a water tank (18 m3) located under the building. This tank also serves as a gigantic seasonal thermal energy buffer by providing the relatively light structure with an indirect additional thermal mass.
A photovoltaic system (97 m²) supplies the building with electricity; the PV system is also supported by the rapeseed oil-driven CHP unit at peak periods. Apart from the fuel required for this unit, the Refuge du Goûter is only dependent on an external supply of cooking gas. The relative cost of gaining the energy needed to cater for 120 hungry people on site, would have been very high.
As well as there not being any gas or power network to connect to at an altitude of 3,800 metres above sea level, there is – not surprisingly – also no water connection. The mountain hut therefore has to obtain the potable water it requires independently and purify the waste water in the building. The snow melting system is used to gain drinking water, while waste water is led to a small sewage treatment plant, where it is treated biologically, oxygenated and finally filtered. The water produced can either be used for the toilet flushing system or returned to the environment.
Ecological balance: 80% of global warming potential due to flights
The ecological balance of the Refuge du Goûter is also rather unusual: the construction, utilisation and later deconstruction of the building is estimated to give rise to a total emission of 534 tonnes of CO2, with 440 tonnes of these alone due to helicopter flights. This figure illustrates why lightweight construction played such an important role in this project. The mountain hut is economical mainly through the large proportion of renewable energies that it uses. Calculations by eco-balance experts showed that the renewable energies alone allowed a 43% saving in CO2 emissions (compared to a fossil-fuel-driven structure of the same construction and size).
Client: Club Alpin Français, Paris
Architects: Groupe H, Paris; Décalage Architecture, Chamonix
Wood construction engineers: Charpente Concept, Paris
Supporting structure engineers (foundations): Betech SA, Anemase
Heating/Ventilation/Sanitation systems engineers: Cabinet Strem, Lyon
Thermal simulation: Albedo Energie, Bourget du Lac
Cost calculation: Cabinet Denizou, Villeurbanne