Heat Recovery Ventilation System (MVHR): How It Works and What It Costs in Ireland
Short answer: a heat recovery ventilation system (MVHR, mechanical ventilation with heat recovery) is one central unit, usually in the attic or a utility room, that runs day and night. It takes damp, stale air out of the kitchen, bathrooms and utility room, brings filtered fresh air into the bedrooms and living rooms, and passes both air streams through a heat exchanger, so the fresh air comes in already warmed. A good unit keeps around 90% of the heat that ordinary extract fans throw away.
How a heat recovery ventilation system works
- Extract. Ducts draw warm, moist air from the wet rooms (kitchen, bathrooms, en-suites, utility, WC) back to the unit.
- Heat exchange. Inside the unit the outgoing air warms the incoming air through thin plates. The two air streams never mix.
- Filter. Fresh air from outside passes a filter before it reaches the house, which keeps out most dust, pollen and insects.
- Supply. The warmed, filtered air goes to the bedrooms, living room and other habitable rooms through ducts and ceiling valves.
- Exhaust. The cooled stale air leaves through a wall or roof terminal, away from the fresh-air intake.
Most of the time the unit runs at a low, quiet rate. It boosts when someone showers or cooks, from a switch, a humidity sensor or the app. In summer a bypass sends the fresh air around the heat exchanger, so cool night air comes in without being warmed.
How much heat does MVHR really recover?
Part L sets the minimum: a heat recovery unit in a new home must recover at least 70% of the heat. Good units do much better. The figure that counts is the one tested to I.S. EN 13141-7 and listed in the SAP Product Characteristics Database (PCDB), because that is the figure DEAP uses for your BER. For example, the Vent-Axia Econiq S we fit is listed at 89–93% heat recovery, depending on the number of wet rooms.
In the house, the result depends on the installation. Ducts in a cold attic must be insulated, the filters must be kept clean, and the system must be balanced: the supply equal to the extract or up to 15% higher.
What it costs to run
An MVHR unit runs all the time, but its fans use far less than their maximum power: a fan at half speed draws only about an eighth of its full power. Lab tests in the PCDB put a well-sized unit at about 20–30 W on its normal setting; the Econiq S, for example, draws about 20 W for a typical three-bed house. With boost on now and then, count on an average of about 25–35 W: 220–310 kWh a year, or about €70–100 at today’s average price of 33c per kWh.
Upkeep: change or clean the filters once a year and have the unit serviced every two years, as Vent-Axia recommends. See MVHR filters and ventilation servicing.
How quiet should MVHR be?
TGD F recommends that a ventilation system on its normal rate makes no more than 30 dB(A) in bedrooms and living rooms, and no more than 35 dB(A) in kitchens and bathrooms. A unit that is too small, or ducts that are too narrow or too few, force the air through too fast, and the valves hum. You hear it most at night and in the bathroom.
The quick fix we often see is turning the unit down. The hum goes, but so do the airflows Part F requires, and once a house has been validated nobody measures them again. The real fix is a unit and ducts sized to run quietly at the right airflow.
What a heat recovery ventilation system costs in Ireland
For a new build, a whole-house MVHR system from Eco Vent Ireland costs, including 13.5% VAT:
| Floor area | Typical price (incl. VAT) |
|---|---|
| Up to 100 m² | from €6,200 (Vent-Axia Econiq S) |
| 150 m² | ≈ €6,700 (Econiq S) |
| 200 m² | ≈ €7,050 (Econiq M) |
| 250 m² | ≈ €7,400 (Econiq M) |
| Over 250 m² | from €8,400 (Econiq L) |
The price covers the unit, ductwork, air valves and plenum boxes, wall cowls, the condensate drain, the ventilation design, commissioning and airflow balancing. Each level with ducting above two adds €400. Travel is free within 100 km of Portlaoise, then €0.60 per km. The exact price comes from your house plans, no site visit needed: get the price for your floor area, or read the full cost guide.
MVHR or cMEV?
TGD F 2019 gives natural ventilation (background vents with extract fans) only for homes with an air permeability between 3 and 5 m³/(h·m²) at 50 Pa. Most new A-rated homes test tighter than 3, and Part L recommends below 3 when mechanical ventilation is fitted. So most new homes need a mechanical system: centralised extract (cMEV, also called MEV) or MVHR.
| cMEV | MVHR | |
|---|---|---|
| Fresh air comes in | through background vents in the windows or walls, 2,500 mm² in each room | through ducts, filtered and warmed |
| Heat recovery | none | around 90% |
| Ducts | extract only, from the wet rooms | supply and extract, to every room |
| Installed price (incl. VAT) | ≈ €2,200–3,000; zoned DucoBox Focus ≈ €4,200–4,800 | from €6,200, by floor area |
| Best for | tighter budgets, homes where supply ducts won’t fit | comfort, lower heating bills, allergies, homes near busy roads |
Eco Vent’s view
The building regulations treat MVHR and cMEV as equal ways to meet Part F, and a new home can reach an A BER with either. We think MVHR deserves more credit. It is the more comfortable system: no vents letting cold air in, warmed and filtered fresh air in every room, real relief for anyone with hay fever or allergies, and lower heating bills because the heat stays in the house. On our NZEB ventilation course the tutor put it simply: MVHR is the best system on the market.
At a Vent-Axia training day we heard that in Belgium and the Netherlands a house with MVHR is worth noticeably more than one with extract-only ventilation, and that the UK industry is now working to get MVHR the same recognition there. Ireland tends to follow the UK: our official Part F installation guide is based on the UK’s Domestic Ventilation Compliance Guide, as its acknowledgements say.
More on cMEV and demand-controlled systems, or see all home ventilation systems compared.
What to look for in a system and an installer
- A design for your house. Room-by-room airflows to TGD F: the whole-house rate is the greater of 0.3 l/s per m² and 5 l/s plus 4 l/s per person, not a unit picked by floor area alone.
- A unit and ducts big enough to run quietly on the normal setting (see the noise levels above).
- A good installer. Ventilation courses make you competent to do the design: the airflows each room needs. Good installation comes from general building skills: drilling neatly through walls, fixing the unit level and square, assembling the ducts, basic plumbing for the condensate trap, and choosing the right parts for the job. The best installers have both.
- Insulated intake and exhaust ducts, the two that run between the unit and the outside wall.
- A condensate drain with a fall and a waterless trap. A leaking or blocked condensate drain is the most common winter fault we see. See servicing.
- Service access. A unit fitted on quick-release couplings opens up in about 10 minutes. See Case Study 7.
- Commissioning with measured airflows in every room, and a commissioning report. TGD F then asks for validation by a competent person certified by an independent third party, such as NSAI. That is a separate service: we give the validator everything they need. See commissioning and airflow balancing.
What MVHR won’t do
MVHR controls indoor humidity and brings in fresh air. It does not heat the house: the warmth it recovers is warmth you have already paid for. It also cannot make old single-glazed or early double-glazed windows warm enough to stay dry on a cold night. If modern low-e double or triple glazing still streams with water, the house has too much moisture inside, and that is a ventilation problem we can help with.
Frequently asked questions
Is MVHR worth it in Ireland?
In an airtight new build, yes: it keeps around 90% of the heat in the ventilation air, filters the air and needs no vents in the windows. If the budget is tight, cMEV meets the regulations for less.
Does MVHR replace my heating?
No. It recovers heat from the air it extracts but adds none of its own. You still need a heating system.
Can MVHR be fitted in an existing house?
Yes. The ducts run through the attic, ceiling voids or boxing. It can be done while you live in the house: expect a few days of noise, dust and work in every room, but it is not as bad as it sounds. The work goes faster in an empty house, so a renovation is the easiest time.
What cooker hood works with MVHR?
A recirculating hood with charcoal filters. The filters trap the grease and the smell, so the air going back into the kitchen is clean, and the MVHR extract in the kitchen takes the moisture outside. Don’t connect a cooker hood to the MVHR ducts: TGD F advises against it, and the grease would coat the ducts and the heat exchanger.
How often does MVHR need a service?
Filters once a year and a full service every two years. A service replaces the filters, cleans the fans, the heat exchanger and the condensate drain, and checks that the unit runs as set.
How long does installation take?
About 3 working days for a 100 m² home and 5 for 200 m². In a new build it is best fitted at first fix, before the ceilings close.
Do I still need trickle vents with MVHR?
No. TGD F asks for background vents with cMEV, not with MVHR, which brings fresh air in through its own ducts.
Building it yourself?
Our DIY kits: designed from your plans, a Vent-Axia or DUCO unit, the Installation App, help while you fit it and our commissioning visit. MVHR kits ≈ €3,800–7,000, cMEV / DCV kits ≈ €1,550–3,500, incl. VAT.
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