« Isolation de la toiture et des combles. Différence ressentie dès l'hiver suivant. Petit retard de planning, mais résultat à la hauteur. »
Thomas R.Mons
Insulation
Insulate first: the number-one source of savings, anywhere in Belgium
The building envelope before the heating: we eliminate heat loss first to gain comfort summer and winter. Roof, walls, floors, façade — each area has its own solution, stackable grants, and a single point of contact from audit to installation.
- Up to 30%
- of losses through the roof
- 6% VAT
- on the works
- Grants
- stackable by area
Our insulation solutions
Every surface, its own solution
Roof, walls, floors, façade, attic: each area has its insulant and its order of priority. Open the one that interests you to understand and compare.
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Roof insulation
The number-one source of savings: it is through the roof that the most heat escapes.
Insulate the roof → -
Wall insulation
From the inside or the outside, depending on your building and the available surface.
Insulate the walls → -
Floor insulation
Cellars and ventilated voids: we cut off the cold rising under your feet.
Insulate the floors → -
Façade insulation (ETI)
Insulate from the outside without losing living space, and refresh the façade.
ETI in detail → -
Attic insulation
Unconverted or converted attics: a quick job with immediate returns.
Insulate the attic → -
Insulating materials
Wool, cellulose, PUR: which insulant to choose for each area and your budget.
Compare the insulants →
Why our projects
Continuous insulation, done in the right order
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Audit & right order of works
We start by identifying heat loss and insulate in the right order — the roof before the rest, not the other way around.
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High-performance materials
Wools, cellulose fibre or PUR: we choose the insulant and thickness suited to each surface, not a single product everywhere.
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Careful installation, airtightness
Insulation is only worth it if it is continuous: no thermal bridge, a carefully fitted vapour barrier, clean finishes.
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Grants & 6% VAT handled
We prepare your application and apply the reduced VAT and renovation grants you are entitled to, area by area.
Insulation near you
An insulation team in your region
Regional grants, local building types, references near you: our city pages give the info that matters where you live.
All our service areas → Prices & grants 2026
How much does your insulation cost?
The price depends on the area insulated, the technique and the surface. Here are concrete benchmarks — and the support that brings the bill down, area by area.
See the prices & grants →* Indicative ranges per m², excluding configuration. Precise estimate during your free audit.
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- Roof insulation
- from €40/m²
- attics or sloping roofs
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- Wall insulation (ETI)
- from €80/m²
- from the outside
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- Renovation grant
- up to 35%
- depending on your income
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- Reduced VAT
- 6%
- home > 10 years old
The right order
Insulation + heat pump: heat less to heat better
Insulate first, then heat: a well-insulated home needs less energy, and a heat pump reaches its full efficiency there. The envelope before the boiler — and a single quote is all it takes.
Discover the heat pump → Insulation ↔ Heating 
Understand everything before insulating your home
Insulating is the move that pays off most in energy renovation: before changing the heating, we eliminate heat leaks. In a Belgian home, the envelope — roof, walls, floors, façade — decides everything: a well-insulated home keeps the heat in winter, stays cool in summer, and consumes far less. But effective insulation cannot be improvised: it all comes down to the order of works and the continuity of the insulating layer.
“The best kWh is the one you never consume: insulating before heating is where the real savings are made.
Insulate in the right order, not all at once
The priority is not the same everywhere: we start where the most heat escapes, then work down area by area. Roof first, walls next, floors for comfort. Here are the options depending on your home :
- Roof Priority no.1
Up to 30% of losses go through the roof. The job with the best return on investment.
Insulate the roof → - Walls Big impact
Second source of heat loss. From the inside or the outside depending on your building.
Insulate the walls → - Floors Underfoot comfort
Cellars and ventilated voids: we remove the cold rising from the bottom of the house.
Insulate the floors →
The roof, the job that pays off most
People often look at the windows, but it is the roof that decides your bill the most: heat leaves through the top. Blown-in insulation for unconverted attics, sloping roofs insulated from the inside, or sarking roof insulation from the outside: the technique depends on your roof structure. We explain the concrete impact on your consumption.
~30%
of heat loss goes through an uninsulated roof. It is the first area to tackle: the job with the best return on investment.
A wendows advisor helps you weigh up the areas, the techniques and the budget — without needless jargon, as our one stop shop approach intends.
Walls: from the inside or the outside?
After the roof, it is the walls that weigh the most. From the inside, it is simpler and cheaper but you lose a little surface; from the outside, you keep your space, eliminate thermal bridges better and renovate the façade. Not everyone falls into the same case : we compare both costed scenarios before deciding. Note too that high-performance window frames make the ideal pairing with well-insulated walls.
Grants, VAT and return on investment
Insulation is one of the best-supported areas : a renovation grant scaled to your income and reduced VAT at 6% for homes more than ten years old. The return on investment is often quick, because the heating bill drops from the very first winter.
We handle the paperwork, not you
Audit, declaration and grants stackable by area: we take care of the application. An overview of the support by region in our grants & support section.
And the installation?
Well-fitted insulation is continuous, with no thermal bridge, and a carefully fitted vapour barrier to guarantee airtightness. It is this detail that separates good insulation from insulation that goes mouldy: our teams master it, and our after-sales service stays reachable over time.
Once the house is insulated, the heating is resized : insulation pairs ideally with a heat pump, which reaches its full efficiency in an airtight envelope. Do you live in a big city ? Our pages on insulation in Brussels, in Liège or in your municipality detail local grants and references.
With wendows, in short
- A free audit that defines the right order of works.
- A clear quote, 6% VAT and grants calculated for you.
- Careful, airtight installation by our teams, after-sales service in Belgium.
Customer reviews
They chose wendows
4.5/5 · 2verified reviews
« Insufflation des murs creux, rapide et sans dégât. La prime régionale a couvert une bonne part. Maison nettement moins froide. »
David K.Huy
Insulation FAQ
Your questions about insulation
Where should I start to insulate? +
We almost always start with the roof: it is through the roof that the most heat escapes, up to 30% of losses. Then come the walls, then the floors. Insulating in the right order avoids spending in the wrong place. Our audit defines the plan area by area, starting from your real heat loss.
Insulation from the inside or the outside? +
Both work, the choice depends on your building. From the inside, it is cheaper and simpler, but you lose a little surface. From the outside (ETI), you keep your living space, eliminate thermal bridges better and renovate the façade, for a higher budget. We compare both costed scenarios before deciding.
Which insulant to choose? +
There is no universal insulant: mineral wool, cellulose fibre, PUR panels or wood fibre each have their strengths depending on the surface, the available thickness and your sensitivity to bio-based materials. We adapt the insulant and thickness to each area rather than imposing a single product everywhere.
What grants are there for insulation? +
Insulation is one of the best-supported areas in Belgium: a renovation grant scaled to your income, sometimes up to 35%, and reduced VAT at 6% for homes more than ten years old. Amounts vary by region and by area. We prepare the application and apply the benefits you are entitled to.
Do I need an energy audit (EPC)? +
An audit is not always mandatory, but it is often recommended — and sometimes required to unlock certain grants or the enhanced renovation grant. It establishes the order of works and quantifies the expected gains. We carry out a diagnosis before the quote to insulate where every euro pays off most.
How long do the works take? +
It depends on the area. Insulating an unconverted attic is often done in one to two days; a roof from the outside or a façade ETI take several days, sometimes one to two weeks depending on the surface. We give you a precise schedule with the quote and keep disruption to the home to a minimum.
Get your free insulation quote within 48h
Free audit, grants calculated, a single point of contact. Describe your project in under a minute.
- Free and no commitment
- 6% VAT & grants handled for you
- Careful installation by our teams