Cost of a
dual-flow VMC.

The ranges below come from our own quotes, prepared between 2024 and 2026 for houses and apartments in Savoie and Haute-Savoie. They are rounded, excluding VAT, and target no client in particular: they say what ventilation costs when our teams install it, not what a catalogue displays.

An honest note on dual-flow. It remains rare in our quotes: only four projects costed, against about thirty in single-flow. The range is therefore wider and should be read as an order of magnitude. Conversely, the price of a hygro B single-flow is very stable from one project to another, because the equipment and installation vary little.

To get to the incl. VAT figure, add 5.5% in most cases (see below): a single-flow at €2,100 excl. VAT comes to roughly €2,220 incl. VAT, a dual-flow at €7,000 excl. VAT to roughly €7,390 incl. VAT.

Single-flow simply extracts. A unit placed in the loft or in a cupboard draws out the damp air from the kitchen, bathroom and WCs, and fresh air enters through air inlets fitted in the window frames or the walls of the bedrooms and living room. In hygro A, only the extract vents adjust their flow to humidity; in hygro B, the air inlets do so too. It is the solution we install most often in renovation.

Dual-flow extracts and supplies. Stale air and fresh air both pass through a unit fitted with a heat exchanger: the outgoing air warms the incoming air without mixing with it. There are no more air inlets in the windows, but a second network of ducts is needed to bring fresh air into each living room.

In both cases, the basic rule remains that of the order of 24 March 1982 on home ventilation: general and permanent ventilation, with air entering through the main rooms and leaving through the service rooms.

The second network. In single-flow, the ducts serve only the wet rooms, often grouped together. In dual-flow, each bedroom and the living room must also be reached. In an existing house, these ducts run through the loft, a suspended ceiling or boxing-in that our plasterers build to hide them: it is this work, more than the unit, that pushes up the quote.

The unit itself is bigger, dearer and has to find a place within the heated volume or in a loft that is accessible for maintenance. Its filters need changing regularly: a unit installed where no one can reach it ends up no longer being maintained.

Core drilling. A fresh-air intake and a stale-air exhaust, set apart from each other, pass through the roof or the facade. In a thick stone wall, these penetrations take more time than the single outlet of a single-flow system.

A dual-flow is only worthwhile if the air passes through it. In an old house with tired windows and doors, floors open to the loft and sockets that let the wind through, cold air enters everywhere except through the unit: the exchanger recovers little, and the investment does not pay back. That is why we only propose it after, or together with, wall insulation and loft insulation that also deal with air leaks.

The reverse is also true: a house that has just been insulated and made airtight can no longer count on its defects to renew its air. Without ventilation to take over, humidity concentrates and mould arrives. On our renovation projects, the VMC is in the same quote as the insulation, installed by the same teams.

One last point specific to our cold lofts: an uninsulated duct that crosses an attic at a few degrees in winter condenses the moisture of the extracted air. On our quotes, the ducts are insulated flexible ducts of 25 mm. If a quote does not specify duct insulation, ask the question.

The reduced rate of 5.5% covers the supply and installation of the ventilation systems listed in the order of 4 December 2024, in force since 1 January 2025, in a home completed more than two years ago:

For an individual dual-flow, the order requires a fixed-rate or humidity-controlled unit of energy class A at least, a temperature ratio of at least 85% and certification by an accredited body (a unit certified NF 205 is deemed compliant). The details of the other rates are in our guide VAT on renovation works.

On grants, do not count on MaPrimeRénov' for a VMC installed on its own: the official France Rénov' page consulted on 29 October 2026 cites, for single-measure aid, only air-to-water or geothermal heat pumps. In a whole-house renovation, ventilation is handled with the rest of the project; our RGE CertiRénov certification (no. CR-2026-73-0095) covers this whole-house renovation offer.

The unit: make, model, single or dual-flow, hygro A or B, number of bathrooms served. This is what allows the VAT rate to be checked.

The vents and air inlets: one line per room, with the location. A timer-controlled kitchen vent and a presence-detecting WC vent do not cost the price of a simple vent.

The ductwork: diameters, lengths, insulated ducts or not, and planned route (loft, suspended ceiling, boxing-in). It is the line most often underestimated.

The exhaust: existing outlet reused, new outlet in the facade or roof cowl. A new roof outlet involves a waterproofing connection.

Commissioning: balancing the flows, test run, electrical connection. Without it, a new VMC may run at a flow that does not match the home.

To place this item within a full budget, see our guide to the cost of a house renovation per m².