« 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 · Floor
Floor insulation: warm-feet comfort, the last leak sealed
The floor accounts for around 10% of a home’s heat loss. In Belgium, many houses have a cellar or a ventilated crawl space: we insulate from below without touching the floor covering. The result: warm feet, a more even floor temperature and a lighter bill.
- ~10%
- of loss through the floor
- From the cellar
- the most common in BE
- Sprayed PUR
- or rigid panels
~10%of loss through the floor
From the cellarwithout touching the floor
Methods
Three ways to insulate the floor
The choice depends on whether there is a cellar and on the type of construction.
- From the cellar The most common in BE
We fix rigid panels (PUR, XPS) or spray PUR foam onto the cellar ceiling. Fast, without touching the existing floor covering.
- From above On the existing floor
We lay a thin insulation layer + screed on the existing floor. Gains performance but raises the floor by 6–10 cm — thresholds and doors need adjusting.
- Within the slab In new builds
The insulation (PUR, XPS) is integrated into the slab during construction or a major renovation. Compatible with underfloor heating.
- Target U-value Umax 0.24 W/m²K
The threshold for regional grants. With 8–10 cm of PUR on the cellar ceiling, you generally reach it.
- Humidity To be treated
If the cellar is damp, we treat the humidity before insulating. Closed-cell PUR foam withstands ambient humidity well.
- Compatibility Underfloor heating
Floor insulation is essential under underfloor heating: without it, the heat goes down into the basement instead of rising.
* Indicative values. The method and thickness depend on the configuration — diagnosis during the on-site survey.
In full transparency
From the cellar or from above?
Two main approaches depending on whether you have an accessible cellar.
From the cellar (the most common)
- Without touching the existing floorThe floor covering stays in place. No need to move out.
- FastSpraying PUR onto the cellar ceiling takes a few hours.
- Moderate budgetThe cost per m² is reasonable because the work is straightforward.
- No raisingNo change to thresholds, doors or stairs.
From above (screed on insulation)
- Maximum performanceInsulation from above eliminates the thermal bridges of the floor.
- Compatible with underfloor heatingWe integrate the insulation and the underfloor heating into the same screed.
- Insulation + new coveringIf the floor needs redoing, we combine insulation with new tiling/flooring.
- Increased performanceThickness not limited by cellar height — we lay as much as needed.
For which basement
Which method for your house?
The choice depends on whether there is a cellar and on the overall project.
-
Accessible cellar
The most common case in Belgium. We spray PUR or fix panels onto the cellar ceiling. Fast and effective.
-
Floor renovation
If the floor is being redone (extension, new covering), we integrate the insulation into the screed. Ideal with underfloor heating.
-
Ventilated crawl space
A crawl space under the house. We access it to fix panels or spray PUR. More constraining but feasible.
And underfloor heating?
Floor insulation is a prerequisite for underfloor heating. Without insulation, the heat goes down into the basement. Combine the two for maximum heat pump efficiency.
Glissez la poignée pour comparer
Real case · house with cellar, Wavre
PUR sprayed onto the cellar ceiling in 3 hours, warm feet
A ground floor with cold feet despite the heating. We sprayed 10 cm of PUR onto the cellar ceiling in 3 hours. The ground-floor surface temperature rose by 3 °C. No more cold underfoot, even barefoot.
- +3 °Con the ground floor
- 3 hoursof work
- −12%on heating
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 methods
From the cellar, from above or within the slab?
The choice depends on your basement and your project.
| Critère | From the cellarVous êtes ici | From aboveVoir la gamme → | Within the slabVoir la gamme → |
|---|---|---|---|
| Price | The gentlest | Mid-range | Within the build budget |
| Work | A few hours | A few days | Built into the project |
| Covering kept | Yes | No (new floor) | Not applicable (new build) |
| Raising | None | 6–10 cm | None (within slab) |
| Underfloor heating | No | Yes | Yes |
| Performance | Good | Very good | Very good |
| Ideal for | Accessible cellar, budget | Floor renovation, heat pump | New construction |
Indicative benchmarks. The optimal method depends on your basement — diagnosis during the on-site survey.
- priority no.1
Roof insulation
30% of heat loss through the roof — tackle this first.
See the roof → - 2nd priority
Wall insulation
25% of heat loss through the walls — injection or EWI.
See the walls → - pair it with
Underfloor heating
Floor insulation is the prerequisite for underfloor heating.
See underfloor heating → - which material
Materials
PUR, XPS, wool: compare the floor insulation materials.
Compare → - pair it with
Heat pump
Insulate the floor before installing a heat pump — to avoid oversizing it.
See heat pumps → - ↑ category
All insulation
An overview of our insulation solutions in Belgium.
Back to the insulation guide →
Indicative price 2026
How much does floor insulation cost?
The price depends on the method and the surface area. Here are benchmarks per m² installed.
See detailed insulation prices →* Indicative ranges per m² installed. The exact price depends on accessibility and cellar height.
- Sprayed PUR on cellar ceiling 25–45 €/m²8–10 cm sprayed
- Rigid panels in cellar 20–40 €/m²PUR/XPS fixed
- Insulating screed from above 50–90 €/m²insulation + screed
- Renovation grant depending on regionWallonia or Brussels
Floor insulation FAQ
Your questions about floor insulation
Can the floor be insulated without breaking up the tiling? +
Yes, if you have an accessible cellar. We insulate at the cellar ceiling (from below), without touching the ground-floor covering. This is the most common and least invasive method.
My cellar is damp, can I still insulate? +
Yes, provided the humidity is treated first (drainage, ventilation). Closed-cell PUR foam withstands ambient humidity well and does not absorb water.
How thick should the insulation be on a cellar ceiling? +
To reach Umax 0.24 W/m²K, allow 8 to 10 cm of PUR (λ 0.028) or 12 to 14 cm of XPS (λ 0.034). The thickness depends on the material and the make-up of the existing floor.
Does floor insulation really improve comfort? +
Yes, very noticeably. The floor surface temperature can rise by 3 to 5 °C, eliminating the cold underfoot even barefoot. The gain is immediate and very perceptible.
Should the floor be insulated before underfloor heating? +
Absolutely. Without insulation, the heat from the underfloor heating goes down into the basement instead of rising. The insulation is laid under the pipes, within the screed.
Which grants apply to floor insulation? +
Regional grants apply if the U-value reaches the threshold (≤ 0.24 W/m²K). VAT at 6% for renovation (home > 10 years old). The amounts vary by region and your income.
Get your free floor insulation quote within 48h
Free basement diagnosis, choice of method, grants calculated. Describe your project in under a minute.
- Free and no obligation
- Cellar/crawl-space diagnosis included
- Installed by our certified teams