Roof Insulation: The Complete Guide
In direct contact with outside temperatures and winds, prone to hot air leaks from inside and cold from outside, the roof is the primary source of heat loss in a house. Good insulation is therefore essential, and represents energy savings as well as better thermal and sound comfort.
Insulation from the inside and insulation from the outside
Today, it is possible to insulate your roof from the inside as well as from the outside.
By decurling or by sarking, exterior insulation consists of isolating the space between the roof frame and the tiles or the exterior material. Very effective, exterior insulation also has the advantage of being carried out from the outside, without the drawbacks of conventional construction sites: less dust, no impact on interior fittings ... The method remains more expensive, however, with more construction. important only for insulation from the inside. It is not compatible with all types of buildings.
For all types of roofs, insulation from the inside is more common. It consists of placing a layer of insulation on the frame. Easier to implement, the site is less expensive than external insulation. The insulation is effective both thermally and acoustically, but the technique reduces interior space.
Renovation or construction, interior design or energy savings, budget ... the objectives and specificities of your project will guide the choice for interior or exterior insulation.
Interior insulation techniques
Converted attic or not, areas difficult to access, steep slope or not ... depending on the type of roof, the techniques must be adapted.
Areas that are difficult to access and uninhabitable attics are generally insulated by blowing, which consists of blowing flakes of insulation: loose, the insulation can go anywhere, and quickly. Slower, the spreading technique is more or less the same, but carried out manually: the insulating flakes are distributed with a rake.
For accessible attics, the insulation can be installed in the form of panels fixed between the rafters of the roof, or in rolls, installed over any desired length. Easy to handle, adaptable, they are widely used.
For optimal insulation, these techniques are combined with the installation of an under-roofing film, as an exterior installation, in the event of a complete roof repair or construction. Placed on the frame or on the thermal insulation and before the roofing, it protects the roof from infiltration, insects and birds, mold… Often recommended, the installation of the under-roof film is sometimes mandatory.
In the same way, if it is strongly advised, the installation of a vapor barrier film can sometimes be obligatory. It prevents the stagnation of condensation and water vapor naturally released by the household.
Roof insulation materials
For insulation from the outside, the most used materials are synthetic insulation such as expanded or extruded polystyrene, or even polyurethane. With a low thickness, they provide very good thermal insulation and good sound insulation .
From the inside, mineral wools - glass or rock - have the best performance / price ratio, for excellent sound and thermal insulation. They settle everywhere, but fear humidity.
Despite their advantages, natural insulation remains little used. Vegetable or animal wool, feathers, wadding, clay… they are a natural resource that is not harmful to humans or the environment, and they regulate humidity and heat exchange between the interior and the exterior. If they last over time, they are more expensive than other insulators, and while the thermal insulation is excellent, the sound insulation is not the best.
Thin insulators such as PMR, IMR, thermo-reflective insulators are only used in addition.