Loft floors
Blown mineral wool, cellulose or wood fibre through the hatch: in a day, without entering the living areas.
From €21 incl. VAT per m²
EstimateInsulation · lofts, sloping roofs, walls
Loft and wall insulation in Nantes
Loft floors in a single day, sloping roofs and internal walls with insulation suited to Nantes buildings, including stone and tuffeau.
- Bio-based insulation
- 5.5% VAT
- 1 to 8 days on site
01 — Why start here
The roof, the first leak
In a poorly insulated house, the roof lets 25 to 30% of the heat escape and the walls 20 to 25% (ADEME orders of magnitude). Insulating the loft is often the most cost-effective job: one day of work, a heating bill that drops from the first winter.
Summer matters too: under a slate roof, a bedroom can exceed 30 °C. Dense insulation (cellulose, wood fibre) delays the heat by several hours.
02 — Our solutions
Three jobs, three durations
Loft floors: 1 day. Sloping roofs: 2 to 6 days. Walls: 2 to 8 days depending on area.
Sloping roofs and loft conversions
Insulation in two crossed layers, continuous vapour barrier, plasterboard: a room that’s warm in winter and liveable in summer.
From €58 incl. VAT per m²
EstimateInternal walls
Framing, insulation and plasterboard; breathable wood fibre for stone and tuffeau walls.
From €52 incl. VAT per m²
Estimate03 — Which insulation?
Comparing insulation materials
For loft floors, at equal thermal resistance (R = 7). Prices incl. VAT, supplied and fitted per m², Essential finish, 5.5% VAT.
| Insulation | Thickness for R = 7 | Summer comfort | Bio-based | Old walls | Guide price incl. VAT per m² |
|---|---|---|---|---|---|
| Glass wool | 32 cm | Low | No | No (unless with a suitable vapour barrier) | €21–€29 |
| Rock wool | 30 cm | Medium | No | Partly | €23–€31 |
| Cellulose wadding | 28 cm | Good | Yes | Yes | €25–€34 |
| Wood fibre | 30 cm | Very good | Yes | Yes, breathable | €31–€43 |
Stone and tuffeau walls: we fit breathable insulation — wood fibre — with a moisture-regulating vapour barrier, so as not to trap damp in old walls. A sealed polystyrene lining on a wall that “breathes” often ends up mouldy.
04 — Target performance
The thresholds we aim for
R ≥ 7loft floors
R ≥ 6sloping roofs
R ≥ 3.7walls
These are the thresholds for the 5.5% VAT rate and for grants. Our Comfort and Signature finishes go beyond them (R = 8.5 and 10 for loft floors).
Grants and VAT, honestly
VAT is 5.5% for insulation of a home completed more than 2 years ago, by simple mention on the quote. MaPrimeRénov’ and CEE bonuses require an RGE-qualified company; France Rénov’ (new tab) advice is free.
Fictional brand: VERAC RÉNOVATION claims no RGE qualification. On a real website, the qualification, its number and the verification link on the France Rénov’ directory would appear here.
Beware of cold calling: we never call without a request from you. Cold calling for energy-renovation work has been banned since the law of 24 July 2020.
05 — Landlords
Energy ratings (DPE): the letting timetable
A home that uses too much energy can no longer be let. Insulating the loft and walls often gains one or two classes.
2025
G Homes rated G: banned from letting since 1 January 2025.
2028
F Homes rated F: banned from letting from 2028.
2034
E Homes rated E: banned from letting from 2034.
06 — Before / after
Insulate, then live in the loft
Wood fibre in the sloping roof for summer comfort: 25 °C in the bedroom when it was 34 °C outside, according to the owners.
- Town
- Orvault
- Duration
- 3 weeks
- Budget incl. VAT
- €12,000 – €14,000
07 — 2026 guide prices
How much does insulation cost?
Price per m², supplied and fitted, 5.5% VAT for a home more than 2 years old.
| Service and material | Guide price incl. VAT | Unit | VAT |
|---|---|---|---|
| Loft floor insulation — Blown glass wool | €21 – €29 | per m² | 5.5% |
| Loft floor insulation — Blown rock wool | €23 – €31 | per m² | 5.5% |
| Loft floor insulation — Blown cellulose wadding | €25 – €34 | per m² | 5.5% |
| Loft floor insulation — Blown wood fibre | €31 – €43 | per m² | 5.5% |
| Loft conversion (sloping roof and plasterboard) — Glass wool and plasterboard | €58 – €80 | per m² | 5.5% |
| Loft conversion (sloping roof and plasterboard) — Cellulose wadding panels and plasterboard | €68 – €93 | per m² | 5.5% |
| Loft conversion (sloping roof and plasterboard) — Wood fibre and plasterboard | €73 – €101 | per m² | 5.5% |
| Internal wall insulation — Mineral wool on framing and plasterboard | €52 – €74 | per m² | 5.5% |
| Internal wall insulation — Wood fibre, vapour barrier and plasterboard | €68 – €95 | per m² | 5.5% |
| Internal wall insulation — Polyurethane board and plasterboard | €58 – €80 | per m² | 5.5% |
2026 prices, supplied and fitted, Essential finish, options excluded. Comfort: +15%, Signature: +32%. Home completed more than 2 years ago; 20% VAT for a more recent home.
08 — Frequently asked questions
Insulation: your questions
Loft floors in a single day, really?
Yes, up to about 100 m². Blowing is done from the hatch or the lorry, without going through your living areas. Beyond that, or if the old insulation has to be removed, allow one more day.
Which insulation should I choose?
Mineral wools are the most economical. Cellulose wadding and wood fibre, which are bio-based, keep cool better in summer. For a stone or tuffeau wall, breathable wood fibre is the safest.
Am I entitled to grants?
MaPrimeRénov’ and CEE bonuses require an RGE-qualified company. France Rénov’ advice is free and impartial. Fictional brand: VERAC RÉNOVATION claims no RGE qualification; on a real website, its number and verification link would appear here.
Someone is calling me on your behalf about bargain-price insulation?
It isn’t us: cold calling is banned for energy-renovation work. Don’t give any information and hang up. We only call back people who have contacted us.
From plan to fitting, one team
Let’s talk about your project
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