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Insulation: long live natural materials!

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As efficient as traditional materials, natural insulation preserves the authentic character of your home. Some even provide you with finishing work ... An overview of nine questions and answers.

Thanks to the environmental awareness of consumers, insulating materials based on plant or animal fibers are coming out of the margins. Although they still represent only 2% of the insulation market (against 5% of our German neighbors), they are developing rapidly by finding different fields of application in new construction and renovation (walls, floors, roofs). "Sheep wool, duck feathers, cellulose wadding ... the references are multiplying.This effervescence reflects not only the interest of professionals, but also that of consumers," says Bernard Abraham, head of the hygrothermal division at CSTB (Scientific Center and building technology). Result: their marketing begins to become widespread.

1. Why choose a natural insulation?

In addition to the thermal comfort they provide, natural insulins of animal or vegetable origin have a low impact on the environment and the health of the occupants. Indeed, their manufacture requires little energy and they emit no toxic gas during their combustion.

2. Are natural insulation as good as traditional materials?

Like mineral wool and EPS (expanded or extruded polystyrene), the thermal performance of natural insulators is a function of their thermal conductivity coefficient, called lambda. This coefficient is expressed in watts per meter and per degree Celsius (W / m ° C) or Kelvin (W / m ° K). The lower the coefficient, the more insulating the material. The effectiveness of the insulation varies depending on where it is laid. Some, like hemp, show a performance similar to traditional materials.

3. Do natural insulators receive certifications?

The Acermi * organization has developed a certification guaranteeing their performance. This certification classifies materials according to 6 criteria: thermal resistance, incompressibility, mechanical behavior, dimensional stability, water behavior and water vapor transfer. 25 insulators are certified, including cork, wood fiber, wood wool ... You can also refer to CSTB technical notices (AT). 12 notices have already been awarded, including hemp, cotton, cellulose wadding, sheep's wool, etc. The certification makes it possible to obtain a decennial guarantee, necessary in case of fire for example.

4. Do they fear moisture?

Natural insulators of vegetable origin do not support the presence of permanent moisture. It is therefore advisable not to install them in contact with damp walls. For old walls, if you can not solve the moisture problem, keep a ventilated air gap between the wall and the insulation. To fight against water vapor (contained in heated air), it is recommended the application of a vapor barrier. On the other hand, cork (in the form of panels of 0.50 x 1 m) is suitable for rooms subject to humidity, such as the basement (cellar), underground rooms and adjoining walls.

5. Are they rodent resistant?

Whether the insulators are natural or not, the rodents all like them, which causes settlements and crumbling. It is therefore recommended to protect the vents well, and effectively block the junctions between walls and roofs.

6. What are the most suitable products for insulating interior walls?

The simplest solution is to glue or stick on the walls of rigid panels (expanded cork, straw, wood wool). It is also possible to apply semi-rigid panels of hemp wool, flax, cellulose or duck feathers. In this case, the panels will be slipped into the studs of the frames. Alternative: Pressurized insufflation of loose insulation through the cladding board. You can use wool (wood, hemp) or expanded cork granules ... Finally, some loose insulation (such as cellulose wool) can be applied by wet spraying on the walls. After drying, we put facing panels, then we finish.

7. Do these materials provide good sound insulation?

Yes, and they can also be effective against so-called air noises (such as voice or music) and impact noises (steps on a floor, shocks). It can be used to insulate the floor. Depending on the nature of the floor, you can pour or directly infuse wool (cellulose, wood, linen, etc.) into the floor. Another choice: the application, under the finish (parquet, tiles), wool panels (wood, linen), rolls of hemp or sheep wool.

8. What finishes can be applied?

As for traditional insulation, we apply siding (type Fermacell), on which we put the finish of his choice (paintings, etc.). But some insulators can receive natural decorative coatings directly. This is the case of wood fiber, on which you can apply a coat of lime. Then you can simply smooth the lime, white or colored, or apply a coating color earth, or a paint, preferably natural (Biofa, Auro ...). Finally, some insulation, such as hemp concrete (mixture of lime, hemp and water), do not require the addition of a finish. The insulation is projected on the wall manually or mechanically (CTC company). This then has the appearance of a coating of gray color, which can be tinted. In addition to good thermal insulation, hemp concrete can restore old buildings without removing the architectural details (frames).

9. Where to find natural insulation?

They are, for the most part, available in the specialized networks (Well-being Materials, Healthy Housing, Eco House, Nature and Habitat), and more and more present in the shelves of wholesalers in materials (Point P, Networks Pros, Denis Materials). On the other hand, apart from hemp wool and cellulose wadding, it is practically not found in DIY superstores (Castorama, Leroy Merlin). Some distributors are waiting for certifications to get started. But prices remain high: € 12 per m² of hemp wool (thickness 10 cm) and € 30 per m² for cork panels, compared with € 4.50 per m2 of glass wool (thickness of 10 cm).

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