Roof insulation: the complete guide
Directly in contact with the outside, the roof is the part of the house that is most subject to heat loss in winter and to air heating in summer: good attic insulation is therefore essential. Converted attic or lost attic, find the best Insulation solution.
Insulation of habitable attics
Bedrooms, games room, office…: to gain living space, it is sometimes useful to fit out the attic of the house. It should be noted, however, that not all constructions are suitable: the ideal structure remains the traditional frame, for a living height of approximately 1.80 m.
The space must be large enough to be furnished, bright and above all well insulated: both thermal comfort and sound comfort must be optimized without reducing the living space. Favor the most efficient techniques and materials for little thickness.
For excellent technical performance of the entire building, exterior insulation has the advantage of not taking up any space in the living space. It consists of placing an insulation - often synthetic such as expanded polystyrene or polyurethane -, in association with a film under the roof, between the frame and the roof.
More rarely, a loose insulation can be injected, as for lost attics, in large bags placed between the rafters of the frame.
Very effective, insulation from the outside cannot however be applied to all buildings, and remains more expensive than insulation from the inside.
For interior roof space insulation, which is easier to install, choose from so-called “creeping” insulation, in rolls to be installed lengthwise, or in panels, to be attached to the rafters. The materials used are mineral, vegetable or even animal wools, which have an excellent relationship between performance and price.
Good ventilation is an essential criterion for good insulation: it remains essential to install a vapor barrier film to limit the stagnation of moisture from water vapor, and possibly a ventilation system.
For windows, prefer double glazing for better sound insulation, and low-emission glass quality for good thermal resistance, essential in summer.
Insulation of "lost" attics
The so-called “lost” attic is the attic that cannot be lived in as it is, without work. If they do not have to be particularly comfortable for everyday life, they cannot do without good thermal insulation .
The materials and techniques used vary according to the accessibility of the space.
For roofs that are difficult to access, blowing or spreading is used: with a blower or manually, with a rake, the bulk material is distributed in the space to be isolated. Rock wool, glass wool, cellulose wadding, hemp, sheep's wool… ecological, natural materials are excellent thermal insulators.
For more easily accessible roof spaces, the simplest and most effective solution remains the unwinding of insulating rolls.