How much does cavity wall insulation cost in 2026? Price per m², total cost & savings

Nu-Isoleren generally uses an indicative price of €21 to €25 per m² excluding VAT.

This price provides an initial indication rather than a fixed price for every property. Two homes with the same external wall area can be very different from a technical point of view.

The final price depends on:

• the number of square metres of cavity wall to be insulated;

• the width and condition of the cavity;

• any debris or existing insulation;

• accessibility of the façade;

• any preparatory work required.

Our prices page also contains our indicative prices and useful calculation tools for your home.

With an indicative price of €21 to €25 per m² excluding VAT, you can already make an initial estimate of the required budget.

Where the reduced 6% VAT rate applies to your renovation, some examples are:

For approximately 100 m² of external wall, the indicative cost is therefore €2,100 to €2,500 excluding VAT, or €2,226 to €2,650 including 6% VAT where the reduced rate applies.

The floor area of your home is not the same as the external wall area to be insulated. Windows, doors, property type and façade dimensions all affect the actual area.

Surface area is important, but it is not the only factor that determines the final cost of cavity wall insulation.

1. External wall area
The larger the external wall area, the more insulation material and labour are required.

2. Cavity width and condition
Before carrying out the work, we check whether the cavity is sufficiently wide, dry and technically suitable for insulation.

3. Debris or old insulation
Mortar, rubble or existing insulation can prevent correct installation. In some properties, the cavity may first need to be cleaned or emptied.

4. Accessibility
Property height, extensions, conservatories and other obstacles can affect the work.

5. Condition of the façade
Damaged pointing, moisture problems or other defects may need to be addressed before insulation.

6. Insulation material
For suitable cavity walls, Nu-Isoleren uses Isomo EPS beads installed as part of an ATG-certified system.

Want to know more about the material? Read our page about EPS insulation.

All indicative prices in this guide are stated excluding VAT.

For renovation work on a private dwelling that is at least 10 years old, Belgium's reduced 6% VAT rate may apply when the legal conditions are met.

For 100 m², this gives the following example:

• indicative price excluding VAT: €2,100 – €2,500

• 6% VAT: €126 – €150

• total including 6% VAT: €2,226 – €2,650

If the property or work does not meet the requirements for the reduced rate, the standard 21% VAT rate may apply.

The VAT rate applicable to your situation will be stated on the final quotation.

In Belgium, grants and financial support for insulation work differ by region. Flanders, Brussels and Wallonia each have their own rules and support systems.

Flanders
Cavity wall insulation may qualify for Mijn VerbouwPremie under the external wall category, subject to the applicable conditions. The rules changed in 2026.

View the current insulation grants in Flanders.

Brussels
The Brussels-Capital Region has its own system of renovation support and financing. The situation regarding renovation grants changed in 2026.

View the current insulation grants in Brussels.

Wallonia
Wallonia also has its own financial support and financing measures for energy renovation and insulation work.

View the current insulation grants in Wallonia.

Because eligibility rules can change, we recommend checking the current rules for the Region in which your property is located before starting the work.

With cavity wall insulation, you can save up to around 25% on your annual heating consumption.

Less heat escapes through the external walls, helping your home retain heat and reducing the amount of energy needed for heating.

Want to know how much you could save for your own home? Use our energy savings calculator.

Cavity wall insulation reduces heat loss through the external walls, but a poorly insulated roof can also allow a significant amount of heat to escape.

If your property has both poorly insulated cavity walls and an inadequately insulated roof, it can be worthwhile addressing both parts of the building.

By combining cavity wall insulation and roof insulation:

• you reduce heat loss through both the walls and the roof;

• your home retains heat more effectively;

• your heating consumption can fall further;

• you improve the energy performance of the property.

In addition to cavity wall insulation, Nu-Isoleren also provides roof insulation using solutions including glass wool, PIR and EPS for certain loft floors.

Learn more on our roof insulation page.

For a property with a technically suitable cavity that is empty or inadequately insulated, cavity wall insulation can be an attractive investment.

The existing cavity is used to improve the insulation of the external walls. Installation is carried out from the outside, meaning that major demolition work inside the property is normally not required.

You can also benefit from:

• less heat loss through the external walls;

• improved indoor comfort;

• lower heating consumption;

• possible grants or financial support;

• improved energy performance of the property.

Whether cavity wall insulation is suitable for your home always depends on the condition of the cavity and façade.

The indicative price of €21 to €25 per m² excluding VAT gives you a useful starting point.

Where the reduced 6% VAT rate applies, 100 m² would for example cost approximately €2,226 to €2,650 including VAT.

The final price depends on the wall area, cavity condition, accessibility and any preparatory work required.

Want to know how much cavity wall insulation will cost for your property?

Request your free, no-obligation quote.