A cost may be offset by aid and tax credits

In 2012, all new buildings must be certified building low consumption (BBC), i.e. consuming less than 50 kWh/m2/year. Horizon 2020, they will be passive energy, before no doubt move to positive energy in 2050. This means that the housing will have to produce their own power. Concretely, it must now take into account all aspects of construction, whether architectural, climatic, technical or economic. The materials selected for the construction are obviously this reflection. In the House, there is the good old block, commonly called concrete block, or the Monomur brick, but also wood. Each of these materials is in a position to respond to the challenges of the Grenelle of the environment What are their respective performance Not easy to find.

There is of course the performance of the material. From this point of view, can information consultant records of environmental and health statements (FDE & S), available on the site. These allow to evaluate the contribution of the different construction products to the environmental and health of a building performance. These sheets should also develop national health environment (NHEP), which provides that, by 2010, 50 of the construction products placed on the market will be subject to labelling with the Plan. Remains that even natural or high-performance material to heat plan is not sufficient to achieve a BBC home.

Bad reputation of concrete

The concrete block is the most used material because it represents 70 of the individual construction. It is very solid (80 tons per linear metre), it offers good performance in terms of acoustics and good resistance to frost and fire. But, that made from natural materials (gravel, sand, cement and water), the concrete does not have good reputation. First of all, because a consists of the cement block, even if it is for only 6 in its composition (this is what can be read on the site of Blocalians). Then because that the manufacture of a block requires the use of a source of energy related to the drying and a quantity of water non-negligible, not only for its manufacture, but for the construction.

Another grievance commonly referred: the obligation to associate with a concrete block insulation Interior based on expanded polystyrene or glass wool, just intercalate between concrete and gypsum. In the end, a wall built in block measuring 40-50 cm thick. The surface of the House is reduced by as much. In addition, the process eliminates difficult thermal bridges. Where energy performance sometimes inadequate.

The Monomur brick is better because it requires no further insulation. Nevertheless that this natural material also has its disadvantages. Not only, it costs more expensive to purchase, but its manufacture is much more intensive than that of the block because it requires a very high temperature cooking.

In short, no material is ideal. Not even wood. Certainly, it is a natural and ecological material insofar as it is quickly renewed. "In Europe, forests are managed sustainably and in France, is cut very few trees to what we could use," explains Philippe Grasse, President of Atlanbois, also constructor of houses in Loire-Atlantique. Another advantage of wood: even cut, he continues to imprison the CO2. "A cubic metre of timber stores 1 tonne of CO2", said Philippe Grasset. In addition, it offers aesthetic qualities that the block and brick are not. And, according to professionals, with a 25-30 cm thick wooden wall, it manages to achieve a very high energy performance building.

Only defect of wood: its price

Similarly, "a home of 120 m2, you win 10 of habitable", said Samuel Mamet, architect specializing in construction wood and comes to realize the first breastfed House BBC Effinergie in Loire-Atlantique. However, the wood has a major disadvantage: its price. According to professionals, the construction of a home wood costs 10-15 more expensive than a traditional House. And a home wood will not necessarily be labeled BBC. "Unlike wisdom, the wood does not obtain more easily the BBC label, explains Michel Stéphan, Trécobat society, presents a little everywhere in Brittany, it is the sum of materials and the techniques which allows." A concrete block House may well reach this level, it is sufficient to increase the thickness of the insulation, and this at a lower cost.

Whatever the material used, the Bill for a BBC Home is not neutral: 10 more than a faithful to thermal Regulation (RT) 2005 House. A cost may be offset by aid and tax credits. And that in turn generates savings. "In BBC, a 100 m2 House costs only 10 euros per month in heating and hot water", concludes Michel Stéphan. In addition, at the time of the energy savings, a labelized House BBC to sell always better than a conventional House. A non-negligible advantage.