« 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 · Facade / EWI
External wall insulation: the continuous envelope that eliminates thermal bridges
EWI (external wall insulation) wraps your house in a layer of insulation covered with render or cladding. The result: every thermal bridge eliminated, no loss of interior space and a refreshed facade. The most efficient form of wall insulation, ideal when the facade needs renovating.
- 0 bridges
- thermal, remaining
- 0 cm
- of interior loss
- Render · cladding
- finishes of your choice
Thermal bridgeseliminated
New facaderender or cladding
Features
What EWI is really worth
External insulation is the most efficient for walls. Here is why.
- Principle Continuous envelope
The insulation is laid continuously across the whole facade, with no interruption. Slabs, lintels and party walls are no longer thermal bridges.
- Performance Umax 0.24 easily
With 12–16 cm of EPS or mineral wool, EWI easily reaches the grant threshold. You can go well beyond with no space constraint.
- Finishes Render or cladding
Mineral or silicone render (RAL shades), wood, fibre-cement or metal cladding. The facade is completely renewed.
- Interior space Untouched
The entire thickness is added outside. No room loses surface area, no furniture to move.
- Humidity Managed
Ventilated cladding lets humidity escape naturally. Mineral render is permeable to water vapour.
- Permit Often required
EWI alters the appearance of the facade. A permit or declaration is often necessary. We handle the paperwork for you.
* Indicative values. The thickness and type of finish depend on the facade — diagnosis during the on-site survey.
In full transparency
Advantages & limits of EWI
EWI is the Rolls-Royce of wall insulation, but it comes at a cost.
What makes it strong
- Thermal bridges eliminatedThe continuous envelope leaves no path for heat to escape.
- No interior lossThe entire thickness is outside — rooms untouched.
- A refreshed facadeNew render or cladding: a facelift and insulation in a single job.
- Maximum performanceUnlimited insulation thickness — you go as far as you like.
What you need to know
- The highest costScaffolding, insulation, finish: the per-m² budget is the largest of all wall insulation.
- Planning permitA change to the exterior appearance — a permit or declaration is often required.
- Duration of the job1 to 3 weeks depending on the surface and finish. Scaffolding required.
- Construction detailsWindow sills, thresholds and roof junctions must be carefully treated.
For which facade
Is EWI right for you?
It is the clear choice when the facade needs renovating or when the walls are solid.
-
Facade to renovate
When the render or brickwork is at the end of its life, EWI combines a facelift and insulation in a single job. Two problems solved at once.
-
Solid walls (no cavity)
No gap to inject. EWI is the best solution for old solid masonry walls.
-
A change of look
EWI with wood or metal cladding radically transforms the look of the house — insulation and design in one job.
Cheaper: injection?
If your walls have a cavity, injection is much faster and cheaper. EWI makes sense when there is no cavity or when the facade needs redoing. And for the roof, see roof insulation.
Glissez la poignée pour comparer
Real case · 1970s house, Charleroi
A deteriorated facade transformed by rendered EWI
A 1970s house with solid walls, a cracked and uninsulated facade. We fitted 14 cm of graphite EPS with white silicone render. Thermal bridges eliminated, facade refreshed and the heating bill cut by 30%.
- −30%on heating
- U = 0.19beyond the grants
- Facadecompletely refreshed
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
Compare the finishes
Rendered EWI, cladding or injection?
The choice of finish changes the budget and the aesthetics.
| Critère | Rendered EWIVous êtes ici | Clad EWIVoir la gamme → | Cavity injectionVoir la gamme → |
|---|---|---|---|
| Performance | Excellent | Excellent | Good (limited by cavity) |
| Thermal bridges | Eliminated | Eliminated | Reduced |
| Price | High | The highest | The gentlest |
| Aesthetics | Smooth render, shades | Wood, metal, fibre-cement | Facade unchanged |
| Permit | Often required | Often required | No |
| Duration of work | 1–3 weeks | 2–4 weeks | A few hours |
| Ideal for | Solid walls, facelift | A change of look | Cavity wall, budget |
Indicative benchmarks. The choice depends on the structure of your walls and the budget — diagnosis during the on-site survey.
- alternative
Wall insulation
Cavity injection or interior lining: the less expensive alternatives.
See wall options → - priority no.1
Roof insulation
30% of heat loss through the roof — tackle this first if not done yet.
See the roof → - which material
Materials
EPS, rock wool, PUR: the material affects both price and performance.
Compare → - pair it with
Windows
EWI is the chance to replace the windows at the same time — optimal junctions.
See the windows → - pair it with
Heat pump
Insulate first, then size the heat pump to an efficient home.
See heat pumps → - ↑ category
All insulation
An overview of our insulation solutions in Belgium.
Back to the guide →
Indicative price 2026
How much does EWI cost?
EWI is the heaviest investment but the most efficient for walls.
See detailed insulation prices →* Indicative ranges per m², scaffolding and finish included. The exact price depends on the height and complexity.
- Rendered EWI (EPS) 100–160 €/m²insulation + render, installed
- Rendered EWI (rock wool) 120–180 €/m²insulation + render, installed
- Clad EWI 150–250 €/m²insulation + cladding, installed
- Renovation grant up to 35%depending on income and region
EWI FAQ
Your questions about external wall insulation
Do I need a permit for EWI? +
Often yes, because EWI alters the exterior appearance of the facade. In Wallonia, a prior declaration or a permit is generally required. We handle the paperwork for you.
Does EWI reduce interior daylight? +
No, if the window sills are properly treated. The thickness added to the facade sets the windows back slightly into the wall, but the impact on daylight is minimal.
Can EWI be done in a co-ownership? +
Yes, with the agreement of the co-ownership. It is even an ideal solution, since the envelope is treated in one go for the whole building.
Render or cladding? +
Render (mineral or silicone) is the most common and the cheapest. Cladding (wood, fibre-cement, metal) offers more aesthetic possibilities and natural ventilation, but costs more.
Does EWI withstand impacts? +
EWI systems incorporate a reinforcing mesh in the render that withstands everyday impacts. On an exposed ground floor, we reinforce the lower zone.
Which grants apply to EWI? +
EWI systematically reaches the Umax 0.24 W/m²K threshold. Regional grants are among the highest for wall insulation. VAT at 6% for renovation.
Get your free EWI quote within 48h
Free facade diagnosis, choice of finish, grants calculated. Describe your project in under a minute.
- Free and no obligation
- Facade diagnosis included
- Installed by our certified teams