What is the point of installing double glazing and opting for an efficient heating system if the degrees gained escape through the roof? We often forget it, but the hot air rises and ends up concentrating under the roof. However, if the latter is not well insulated, more than 30% of the heat will end up outside.
Acting from within to limit costs
To gain thermal and acoustic comfort while reducing your heating bill, it is essential to caulk your frame correctly. It can be done from the inside. An often preferred solution, since it is easy to implement and inexpensive. Count between 20 and 50 euros per square meter.
In practice, this method most often involves the installation of insulation panels between the roof and the partitions. In terms of materials, mineral wool and glass wool are the most widely used. But it is also possible to opt for polystyrene panels with a plaster facing. In any case, it is better to undertake this type of work when the attic is not yet fitted. For lost attics, insulation by material blowing using a specific machine is even easier to achieve.
From the outside to avoid any discomfort
The other option is to act from the outside. For what interest? This allows you to keep as much space as possible under the eaves. Without forgetting a charming asset, since the interior framework remains visible. On the site side, on the other hand, it’s a different story. Unless you proceed before the installation of the roof, in the context of a new construction, the latter must be removed during the renovation work, in order to press the insulation on the rafters and then replace the roof covering by -above. A long and complex operation which costs about three times the insulation from the inside.
Several techniques exist. That of seasoned caissons aims to frame them with a closed chamber. More recent, the sarking method multiplies the protections to eliminate all the faults likely to let air pass: floorboards are nailed to the rafters, a vapor barrier and an insulation ensure the waterproofing, then a rigid plate and a counter-lathing cover the whole. Last solution, the more complex technique of sandwich panels, nested thanks to a system of tabs.
Quality comes at a price
Faced with the challenges of attic insulation, it is better to intervene according to the rules of the art by choosing materials with a thermal resistance of at least 8 m2 / kW and by calling on a craftsman certified RGE (“recognized guarantor environment ‘), in order to benefit from financial aid.
Think in particular of energy saving certificates (CEE), a kind of interested sponsorship through which brands pay for part of your work, all without condition of resources. A version reserved for the most precarious households allows insulation of lost attics for symbolic 1 euro, although a draft decree intends to remove this boost offer on June 30, 2021. In addition, the MaPrimeRénov ‘device makes it possible to finance the work insulation.