Price of wall insulation from the outside in Belgium

2 - The condition of the building to insulate

ITE work can become more complex if the walls to be covered show signs of degradation. It is necessary to diagnose the condition of the walls to ensure the durability of the applied insulation. The surface intended to receive the insulation must be perfectly stable and watertight. This is the time to identify any anomalies in the wall to be insulated:

• holes,
• cracks,
• blisters,
• micro-cracks,
• moisture traces,
• cold walls, etc.

Our craftsmen also identify the source of these defects, whether related to moisture or the aging of materials. This allows for the necessary repairs to prepare an adequate surface for the installation of insulation.

Obviously, the emergence of additional work increases the cost of external insulation. Moreover, insulating an old house can prove to be more expensive. The most common materials in the past (stone, brick, concrete block) often exhibit low thermal performance.

ITE standards were also less strict than today. A greater thickness of insulation may therefore be necessary to achieve an optimal comfort level, which increases the budget. Finally, if a large scaffold needs to be installed to access the facade, this can also influence the overall cost.

3 - The materials used for external insulation

The thermal performance level of the material used to insulate the walls is a determining factor in calculating the final price. Generally, the higher the thermal resistance coefficient, the more expensive the material will be per m².

However, depending on the type of insulation (synthetic, mineral, plant, animal...), the most effective material is not always the most expensive. Here are some price indications for commonly used insulations for external insulation work (thickness 10 cm):

• polyurethane: 20 €/m²,
• expanded or extruded polystyrene: 15 to 20 €/m²,
• phenolic foam: 45 to 50 €/m²,
• flax fiber: 25 to 30 €/m²,
• wood fiber: 15 €/m²,
• cork: 15 to 30 €/m²,
• duck down: 15 to 20 €/m²,
• glass wool or rock wool: 3 to 10 €/m²,
• cellular glass: 10 to 50 €/m².

It is recommended to be accompanied by a certified craftsman like those from Avenir Rénovations to select a material with physico-chemical properties suitable for your project. You can choose the ideal thickness based on the desired energy performance.

4 - The external insulation technique used

The cost of external wall insulation also depends on the chosen insulation method.

Insulation under cladding

The professional installs an insulating + facing system in the form of panels on the facade. The budget ranges from 100 to 150 €/m².

Insulation under render

The insulation is directly applied to the outer wall and then covered with a bonding coat applied over a mesh. The price of external insulation under render ranges from 180 to 220 €/m² supplied and installed.

Insulation under siding

The insulation is placed in a wooden or metal frame and then fixed to the facade using brackets. This structure is covered with siding (wood, composite, PVC, stone, zinc...) and constitutes an aesthetic and durable solution.

The price of external insulation under siding varies between 110 and 160 €/m² supplied and installed. With zinc siding, the cost can reach 250 €/m².