Price of external
insulation per m².

The amounts below come from five external wall insulation quotes drawn up between 2024 and 2026 for houses in Savoie and Haute-Savoie. All relate to external insulation under render, bonded and plugged onto existing masonry. They are rounded and given exclusive of VAT, with the incl.-VAT equivalent at the reduced rate of 5.5%, which applies when the insulation achieves the required performance.

Two lines rather than one. Our quotes separate the insulation and the render, because they are two distinct pieces of work: the board first, the reinforced coat and the finish afterwards. Added together, they give the price per m² found in comparisons. Our pages on external insulation in Aix-les-Bains, Annecy and Chambéry indicate a range of €120 to €190/m² under render: the five projects priced here all fall in the upper part of that range, with at least 130 mm of insulation.

Scaffolding is priced separately. In our quotes, it ranges from €3,000 to €7,600 excl. VAT, erection and dismantling included, for façades of 210 to 295 m². The most expensive does not cover the largest area: the difference comes from the project itself, its height, its access, the protection to be fitted and the hire period.

For a house in the Aix basin priced in 2026, our quote provided for 130 mm expanded polystyrene, with a thermal resistance of R = 4.20 m²·K/W according to the manufacturer's data sheet, bonded and plugged, then a hydraulic render sprayed onto a reinforced mesh, strengthened over the first metre at the foot of the façade to withstand knocks.

Scaffolding and set-up account here for nearly a fifth of the total, about 18%. That is why the price “per m²” of a small façade is always higher: the flat fee is spread over fewer square metres. If all items fall under the 5.5% rate, this pricing comes to about €43,500 incl. VAT.

The insulation and its thickness. On one of our 2024 quotes, the rock wool, wood fibre and polystyrene variants were priced at the same figure, €130 excl. VAT per m² installed. The material therefore matters less than the thickness needed to achieve the target performance: in our quotes, 130 mm of expanded polystyrene gives R = 4.20 m²·K/W, whereas wood fibre needs 160 mm for R = 4.21. Our guides to glass wool or rock wool and wood fibre insulation compare these materials in detail.

Shutters and windows. The thickness of insulation moves the façade away from the hinges and the window reveals. Hinged shutters are refitted on offset hinges, about €650 excl. VAT per shutter on one of our quotes that counted fifteen; roller-shutter boxes fitted on the façade have to be moved. Around windows, our quotes provide for an insulation return of at least 40 mm onto the frame, as recommended by the 2014 RAGE professional rules. Our guide to the price of a roller shutter details the cost of shutters.

Singular points. Window sills, door thresholds, roof overhangs, downpipes, junctions with masonry: each calls for a part or a cut. A façade pierced by many openings costs more per m² than a long blank gable.

The condition of the wall. Render that sounds hollow, cracks or rising damp at the foot of the wall are dealt with before bonding anything. These repairs are not part of the external insulation price per m² and must appear on separate lines of the quote.

The five quotes in this guide relate to external insulation under render, the most common technique on masonry houses. Under cladding, the insulation sits within a frame fixed to the wall, covered by a rainscreen membrane, a ventilated air gap and then the cladding itself: more material and more fitting hours. Our external insulation pages give, as a guide, €160 to €260/m² for this technique, finishing included.

Our recent quotes contain no external insulation under cladding on an existing house: we therefore do not publish a range drawn from our projects. Timber cladding alone, fitted without insulation, comes to €90 to €135 excl. VAT per m² there; only one quote prices aluminium cladding, at €155 excl. VAT per m².

Per square metre, insulating from the inside costs less: an insulating lining on framing comes to €75 to €90 excl. VAT per m² on our quotes, as our guide to the price of plasterboard per m² shows. But the lining takes up living space, means reworking sockets, paintwork and sometimes radiators on the walls concerned, and leaves thermal bridges open at floor junctions.

External insulation costs about twice as much per m² and is done without emptying the house. It is most relevant when the façade has to be redone anyway: the scaffolding and the new render would then be paid for once for two results. Our guide to insulating walls from the inside sets out the cases where the inside remains the only option.

In a dwelling completed more than two years ago, wall insulation is subject to the reduced rate of 5.5% when the insulation installed has a thermal resistance of at least 3.7 m²·K/W (French General Tax Code (code général des impôts), annex IV, article 18 bis). The insulants described in our quotes, from R = 4.20 to 4.21, exceed this threshold. The insulation must also be supplied by the company that installs it: materials bought by yourself remain at 20%.

Scaffolding and the refitting of shutters can follow the same rate when they are made indispensable by the insulation, under the conditions set by the tax authority; otherwise they fall under 10%. Our guide to VAT on renovation work details these rules.

Since 1 September 2026, MaPrimeRénov' no longer funds wall insulation as a single measure: the main measures still funded are heat pumps, excluding air-to-air, and connection to a heat network (order of 25 August 2026). External insulation can still be funded within a major renovation: dwelling rated E, F or G, at least two insulation measures among walls, windows, floors and roof, a gain of at least two energy classes and compulsory support from Mon Accompagnateur Rénov'. The grant then covers 10 to 80% of the work depending on income, within a ceiling of €30,000 or €40,000 excl. VAT depending on the gain achieved. Our page on renovation grants in 2026 details the scales.

Energy-saving certificates (CEE) and the zero-interest eco-loan (éco-PTZ) follow their own conditions, which we check at the quote stage. Our RGE CertiRénov certification (no. CR-2026-73-0095) covers the whole-home renovation offer: it is within that framework, in a major renovation, that we include external insulation in a funded project. In Haute-Savoie, the Département adds a grant for owner-occupiers, presented on our external insulation in Annecy page.

External insulation changes the appearance of the façade: it requires a prior declaration (déclaration préalable) at the town hall, processed in one month when the file is complete, generally two months in a protected area. The local plan (PLU) may impose a colour, a finish or a type of cladding, and a co-ownership must vote the work. Our guide to the prior declaration for works details the file.

When the thickness of insulation encroaches on the neighbouring land or on the PLU setbacks, special rules apply: our external insulation in Aix-les-Bains page explains the right of overhang and the possible derogation from siting rules. Our façade renovation guide covers render, cladding, gutters and insulation in a single budget.