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Architecture: Top Marks for Energy Balance

(May 2011) Hard-core ecologically-minded contemporaries could be a target group for the new building in massive natural stone movement. It promises not only energy savings in building material and healthy living. Recycling, too, has interesting perspectives: a massive stone house can easily be deconstructed and the elements recycled for a later project.

Jean-Paul Foucher analyzed and published facts and figures to one of his projects. He is a stonemason by trade and Director of the Institut de la Pierre.

170 is the magic number around which Foucher’s home in the Southern French Town Millau revolves:

* 170 m² is the living space (comprising one living room, three bedrooms and a 9-m² kitchen as well as two bathrooms and one garage);

* 170.000 € was the price (without the land), placing it in the mainstream consumer price-category of pre-fab housing;

* 170 days was the time it too to build;

140 m³ of Pont du Gard limestone went into construction of the house.

The material costs as a portion of the over-all expenditure were surprisingly low: including transportation a mere 37,300 € or 21.8% of the total budget was spent on stone.

Let us turn to the building as such. It can, perhaps, best be compared to building with Lego-blocks. The quarry delivered stone blocks in a limited number of sizes measuring between 80 and 210 cm in length all 106 cm in height. The breadth or thickness was 30 cm for outside walls and 25 and 10 cm for the interior walls respectively.

As Foucher expounded, producer Pro-Roch worked meticulously thus reducing work on site to a minimum. The gable-end of each block was provided with a furrow for liquid binder of lime and sand. In a subsequent step the joints were sealed and the stone impregnated.

Facts: the masonry was completed by three workers in nine days with the mechanical assistance of a small crane. At the end of 170 days the interior construction was complete.

The roof took on a convex shape commonly seen in Africa. Ceiling height thus reached a max. 3 m. Foucher and architect Matthieu Pinon also relied on age-old methods for the base of the building: first on the foundation comes a layer of hard limestone; it protects the soft limestone above from capillary ascension of moisture.

Outside walls are thickly insulated. This method serves a dual function: it provides cosy warmth inside, and piping and wiring can be installed in the insulating layer leaving the stone practically immaculate for future demolishing and reuse.

With its floor heating, the house draws an average of 49 kilowatt-hrs/m². With improvements such as a solar system a CO2-emission coefficient of 11.4 kg/m² could realistically be attained – by comparison, the figure for concrete is 22 times higher.

As far as consumption of natural resources is concerned, massive houses are also among the forerunners. To set the stones in Millau „2 m³ water, 2 m³ sand and 9 sacks of lime were needed“ according to Foucher.

From an ecological point of view, a massive stone house has nothing but advantages – provided (and this is the flip-side of the coin) the distance from quarry to building site is short.

But there is an interesting target group for building in massive stone: This is the ecologically conscious middle-class who practice what they preach.

Especially small towns, ever shrinking in population, could make a name and an identity for themselves by building in natural stone.

Concrete is not among the main contenders for massive stone as home-building material. „Every year 180,000 new homes are built in France using wood, brick or straw“ according to a publication.

Institut de la Pierre (French)

Ecoinvent

A number of buildings in massive stone were awarded prizes at last year’s Concours d’Architecture Pierre Naturelle. The house in Millau was one of them.

Another was the Wine Museum built in Roman style in the city of Patrimonio. Gilles Perraudin was the architect responsible. We had reported on his ideas regarding massive building in our August 2009 issue.

A wine depot in Montpellier by Fayolle Pilon Architects was also awarded a prize.

As reported in the Swiss trade journal „Kunst+Stein“ (2/2011), it is a five-story house made of 1,300 t of massive granite. The builder and land-lord entertains a real-estate company and a quarry. The publication can be ordered at a cost of 16 SF + shipping and handling from the Verband Schweizer Bildhauer- und Steinmetzmeister (VSBS) (Mail).

Photos with kind permission of the French trade journal „Pierre Actual“.