Roof insulation price in Belgium in 2026
Blown-in for unused lofts, panels between rafters or external sarking: three techniques, three ranges. We explain what makes the bill vary and how regional grants reduce your out-of-pocket cost — up to 50 % for lower incomes.
Indicative ranges, grants not deducted.
Roof insulation price by technique and surface
Ranges for insulation supplied and installed, including labour, fixings and standard finishes. Thicknesses meet the R-values required for the 2026 regional grants.
| Technique | Small surface ≈ 50 m² | Medium surface ≈ 100 m² | Large surface ≈ 150 m² |
|---|---|---|---|
| Blown-in for unused loftscellulose or loose-fill glass wool | 750 – 1 500 € | 1 500 – 3 000 € | 2 250 – 4 500 € |
| Panels under raftersPUR, PIR or rockwool between rafters | 1 500 – 2 750 € | 3 000 – 5 500 € | 4 500 – 8 250 € |
| External sarkingrigid panels laid over or under the covering | 2 500 – 4 500 € | 5 000 – 9 000 € | 7 500 – 13 500 € |
Indicative prices incl. VAT, installation and finishes included, grants not deducted. The exact technique and thickness are determined during the free quote. Grant details: roof grants.
What makes your roof insulation price vary
For the same surface, two quotes can differ by 30 to 50 %. Here are the six items that weigh the most on the final bill.
- Chosen technique
Blown-in for unused lofts is the cheapest technique (15–30 €/m²). Panels under rafters for converted lofts cost 30–55 €/m². External sarking, the most thermally efficient, reaches 50–90 €/m².
Roof insulation guide → - Insulant used
Blown cellulose is economical and ecological. PUR/PIR offers the best thickness/performance ratio. Rockwool brings good fire resistance. Each material has a different cost per m².
- Access to the loft
A loft accessible through a standard hatch reduces installation time. A complex roof structure, low headroom under the ridge or the absence of a floor increase the labour cost.
- Roof structure configuration
A traditional structure with multiple trusses or a steeply pitched roof lengthens installation time, especially for panels between rafters. Flat or very low-pitch roofs require a different technique.
- Interior finish
For converted lofts, a plaster, panelling or OSB board finish is added to the quote. For unused lofts, no finish is needed, which keeps the costs low.
- Roof complexity
Dormers, roof windows, ventilation ducts, flashings around chimneys: each technical detail requires specific treatment that adds to the base price.
The grants that lighten your roof insulation
Roof insulation is the best-subsidised measure in Belgium. Here are the 2026 benchmarks by region — we calculate the amounts and handle the paperwork for you.
Prime Habitation — roof
The Prime Habitation covers roof insulation for existing homes. The amount depends on the income category and the R-value achieved. Lower-income households benefit from significant multiplier coefficients.
- Minimum thermal resistance R ≥ 4.5 m²K/W (R ≥ 6.0 recommended)
- Registered contractor and detailed invoice with R-values
- Prior home audit recommended to maximise the amounts
Renolution — roof insulation
Under the Renolution programme, Bruxelles-Environnement subsidises roof insulation with three income categories. Homes in a priority renovation zone benefit from additional increases.
- U-value ≤ 0.24 W/m²K after works (R ≥ 4.5)
- Home more than 10 years old
- Application submitted within the deadline after the final invoice
Get your price net of grants, within 48h
We check your entitlements, quote net of grant and handle the paperwork: you pay nothing upfront.
- We check your entitlements
Region, income, age of the home: we identify every grant available for your roof.
- We quote net of grant
The quote shows the estimated grant amount and the 6 % VAT applied.
- We handle the application
Forms, technical certificates, compliant invoices: we take care of it all.
- We deduct where possible
The grant is taken off your bill with no cash advance, or paid directly after the works.
In Flanders? The Mijn VerbouwPremie also covers roof insulation — ask us for the details for your municipality.
A range in 10 seconds
Choose the insulation technique and enter the surface for an order of magnitude. The free quote remains the only precise estimate.
Indicative estimate, excluding specific configuration (dormers, complex roof structure, finishes).
What a real quote looks like
A concrete case to make the ranges meaningful — your project will be costed according to your surfaces and the configuration of your roof.
Indicative example dated 2026, unused loft accessible without particular difficulty. Request your quote for a costing tailored to your roof.
Dig deeper before deciding
- Roof insulation Technical guide
Installation techniques, required R-values, the difference between unused/converted lofts and sarking explained in detail.
See the roof guide → - Insulation price (all areas) Comparison
Roof, walls, floor: compare the ranges by area to prioritise your energy renovation project.
Compare prices → - Roof insulation grants Regional subsidies
The details of the Wallonia, Brussels and Flanders grants for the roof: amounts, R conditions and step-by-step procedures.
Explore the grants →
Your questions about roof insulation prices
How much does roof insulation cost in 2026?
For blown-in unused lofts (the most common technique), count on 15 to 30 €/m² installed. For converted lofts with panels between rafters, the range rises to 30–55 €/m². External sarking reaches 50–90 €/m² but does not affect the living space and eliminates all thermal bridges.
What is the difference between blown-in, under-rafters and sarking?
Blown-in for unused lofts suits inaccessible, unconverted attics: the loose-fill insulant is blown in by machine. Panels under rafters are used for converted lofts (attic bedrooms) by sliding the insulant between the rafters. Sarking lays rigid panels over (or under) the covering during a roof recovering.
Do grants really cover half the cost for the roof?
For lower-income households in Wallonia, grants can indeed reach 40 to 50 % of the works amount. For median incomes, count rather on 20 to 30 %. The roof is the best-subsidised area because it offers the best energy gain per euro invested.
Do you have to recover the roof to do sarking?
Not necessarily. Sarking can be done either from the outside (during a roof recovering) or from the inside (without touching the tiles). Internal sarking costs a little less but slightly reduces the headroom under the roof. We assess the most suitable solution during the quote.
What insulant thickness is needed to get the grants?
In Wallonia, the grant requires R ≥ 4.5 m²K/W (R ≥ 6.0 recommended to maximise the subsidies). In Brussels, the Renolution threshold is U ≤ 0.24 W/m²K, i.e. about R ≥ 4.5. This typically corresponds to 27–30 cm of blown cellulose or 12–16 cm of PUR/PIR depending on the products.
Does the installation include checking the roof structure?
Yes. Before any blowing or panel installation, our team inspects the roof structure: condition of the beams, presence of mould, loft ventilation. If treatment or repair is needed, we flag it in the quote before starting.
Your exact price, costed and net of grants
The ranges give the order of magnitude — the quote gives the figure. On-site survey free, grants calculated, a single point of contact. In under a minute.
- Free and with no obligation
- Grants & 6 % VAT calculated and deducted
- Costed quote within 48h business days