Price of roof insulation in Belgium

2 - The total surface area of the roof

The overall surface area of the roof plays an essential role in determining the price. The cost of the work is generally expressed per square meter (m²). The larger the surface area, the higher the total budget will be. A large area to insulate indeed requires more materials and more working time.

3 - The insulation method

The price of thermal insulation for the roof can vary depending on the technique applied. You can insulate a roof from the outside, from the inside, or insulate only the attic floor.

The external insulation method, also known as sarking, involves the complete refurbishment of the roof. It is a suitable solution for houses with flat roofs or those with usable or convertible attics.

The internal insulation technique consists of placing the insulation under the slopes or between the rafters. Insulating the attic floor, often chosen for lost attics, involves spreading or placing the insulation directly on the floor. This option is generally less expensive than the other two.

4 - The choice of insulation

You have access to various insulating materials for roof insulation:

• rock wool,
• cellulose wadding,
• glass wool,
• polystyrene panels,
• wood wool,
• polyurethane foam…

Each insulator has its specific properties. Some materials are more expensive than others, which can influence the final cost depending on your choice.

For example:

• cellulose wadding or rock wool costs between 20 and 35 €/m²;
• glass wool or polystyrene ranges from 10 to 20 €/m².

5 - The thickness of the insulation

A thicker layer can ensure better thermal performance, but it requires a larger quantity of material. Therefore, purchasing a larger volume of insulation increases the total cost. If the thickness required for optimal insulation is high, the price of the work will also be higher.

6 - Preliminary work and finishes

The cost of insulating a roof can increase if preliminary interventions are necessary before installing the insulation, such as:

• complete cleaning of the roof,
• removal of the existing covering,
• repair of the framework,
• installation of a waterproof membrane,
• installation of trims around openings…

These preliminary works as well as any finishes influence not only the cost of materials but also that of labor.