Like pitched roofs, flat roofs must be properly insulated to ensure good performance and optimal thermal comfort in your home. However, their special configuration means that their insulation is carried out with completely different methods than those used for a pitched roof. To achieve the insulation of a flat roof, there are different techniques and here is an overview.
The insulation of the roof of a building is essential to preserve its energy efficiency and thus reduce heating costs. However, it is a complex task that requires precise and careful work, otherwise moisture and structural damage may occur.
Options for a flat or low-pitched roof (insulated)
It is the most popular in Quebec for all new constructions of flat roofs, because it offers very good resistance to climatic variations. This insulation technique is carried out from the outside of the building. It consists of laying a vapour barrier, then insulation (polystyrene or polyisocyanurate panels, or even glass wool, for example) on the roof structure. After being waterproofed, the whole is covered with a waterproof coating (example: elastomeric membrane, TPO, EPDM, or others).
Options for a flat or low-pitched roof (ventilated)
Cold roofing, also called "ventilated roofing", is an insulation technique that is carried out from the inside of the house. Formerly widely used, it is less and less so because of its drawbacks such as water infiltration, the presence of humidity, fungi, mold, etc. It will therefore be especially recommended if the workspace is limited or if the installation of a warm roof is impossible.
For its construction, the thermal insulation is placed (warm side down) under the waterproofing membrane of the roof, leaving an air gap between the two, then a vapour barrier is placed before the final ceiling.
Materials used to insulate a flat roof
The insulation of a flat roof can be done with different types of materials depending on the type of insulation chosen (warm or cold roof) and your budget. The main insulators are :
- Glass wool (mineral wool);
- Blown wool or cellulose;
- Rock fiber (more environmentally friendly mineral wool);
- Expanded polystyrene;
- Spray polyurethane;
Need to replace your attic insulation?
Trust the experts at Couvreur Couv-Toit in Montreal and Laval to properly insulate your flat roof and help you choose the best intervention method for your roof and your budget.