Home Ventilation Systems in Ireland: The Types Compared
Short answer: Irish homes are ventilated in one of three ways: natural ventilation (background vents and extract fans), centralised mechanical extract (cMEV, also called MEV), or whole-house heat recovery (MVHR). Which one fits depends mostly on how airtight the house is. Below 3 m³/(h·m²), which most new builds reach, you need a mechanical system: cMEV or MVHR. Single-room heat recovery units are also sold, but they are not a whole-house system.
MVHR vs cMEV in 3 minutes (video)
The types at a glance
| System | Fresh air comes in | Stale air leaves | Heat recovery | Installed price (incl. VAT) | Fits |
|---|---|---|---|---|---|
| Natural ventilation | background vents in windows or walls | extract fans in wet rooms, opening windows | none | — | houses between 3 and 5 m³/(h·m²), older homes |
| cMEV (MEV) | background vents, 2,500 mm² in each room | one central fan extracts from every wet room, all the time | none | ≈ €2,200–3,000 (zoned ≈ €4,200–4,800) | new builds and renovations on a budget |
| MVHR | ducts, filtered and warmed | ducts from wet rooms, through the heat exchanger | around 90% | from €6,200, by floor area | comfort, lower heating bills, allergies, busy roads |
| Single-room heat recovery | a unit through the wall of the room | the same unit | some, that room only | — | we don’t install them |
What Part F (TGD F 2019) says
- It covers purpose-provided ventilation in homes with an air permeability up to 5 m³/(h·m²) at 50 Pa.
- It gives natural ventilation only for homes between 3 and 5. A house designed above 3 that is built tighter needs additional measures.
- Part L recommends below 3 when mechanical ventilation is fitted.
- The whole-house rate is the greater of 0.3 l/s per m² and 5 l/s plus 4 l/s per person. The system must deliver at least 25% more, and at least the minimum boost rates in the wet rooms: kitchen 13, utility 8, bathroom 8 and WC 6 l/s.
- Noise at the normal rate: no more than 30 dB(A) in bedrooms and living rooms, 35 dB(A) in kitchens and bathrooms.
- The airflow may be adjusted by automatic control, for example by humidity or occupancy. That is what demand control does.
- After commissioning, the system should be validated by a competent person certified by an independent third party, such as NSAI.
Natural ventilation with extract fans
Background vents (trickle vents) let air in, and fans in the kitchen and bathrooms push damp air out when they run. There is no central unit to maintain. The airflow depends on wind and outdoor temperature, the vents let cold air in, and TGD F does not give this option for homes tighter than 3 m³/(h·m²).
cMEV, MEV and demand control
MEV and cMEV (centralised mechanical extract ventilation) are the same thing: some manufacturers label it MEV, others cMEV. Technically it is a fan in a casing with a control board and a humidity sensor. The unit sits in the attic or a cupboard and pulls air from every wet room around the clock, and fresh air comes in through background vents in the other rooms. In Ireland most go in with nothing else, as the cheapest way to meet the minimum in the regulations. That works, but it is not real demand control.
DCV (demand-controlled ventilation) starts from the same unit and makes it smarter. The logic is simple: in winter, every litre of air the unit extracts is replaced by cold outdoor air coming in through the vents, and that cools the house. So DCV moves only as much air as the house needs at that moment, based on what its sensors read, and saves heat. On top of a cMEV it adds:
- More sensors: humidity or CO₂ sensors in the rooms, not only the one inside the unit.
- More control: a controller with several modes and boost on demand, or an app on your phone.
- Zone control: the house split into zones, each ventilated on its own demand (for example the DucoBox Focus with control valves).
- Fresh-air vents that work with the system: vents in the windows or walls that let in only as much outdoor air as the sensors call for. This is DCV at its best.
Why room sensors matter: a cMEV with one humidity sensor inside the unit reads the air of the whole house mixed together. On its way to the unit, the moist air from the bathroom mixes with the air from the kitchen, the utility and the other wet rooms, so the reading rises slowly or hardly at all, and boost comes late or not at all. A humidity sensor in the bathroom sees the shower straight away and starts boost immediately.
Duco makes this easy: sensors such as CO₂ are simple to add, and even the entry-level DucoBox Reno works with Duco’s wireless controls, so adding a DUCO User Controller (€85) already gives you basic demand control. We have yet to see a fully demand-controlled system in an Irish house, and we would like to change that.
cMEV costs little to run. As an estimate, a DucoBox Silent Connect draws about 9 W for a typical house, under €30 a year. The trade-off is that the heat leaves with the extracted air, and the vents let in unheated air. More on cMEV and demand-controlled systems.
MVHR (mechanical ventilation with heat recovery)
Supply and extract ducts reach every room. The unit passes the outgoing air through a heat exchanger and keeps around 90% of its heat in the incoming fresh air, which is also filtered. There are no vents in the windows. In our view it is the best system for an Irish home: more comfortable, cheaper to heat, and a relief for anyone with allergies. It costs more to install, needs room for the ducts and a yearly filter change. How it works and what it costs: heat recovery ventilation system explained and MVHR installation.
Single-room heat recovery units
We don’t install them. A small unit through an external wall ventilates one room and recovers some of its heat, but it serves only that room. Many are sold without independent test data. If you consider one, ask for test results to EN 13141-8, the standard for this kind of unit.
Which system fits your house?
- New build, airtight, heat pump: MVHR, or cMEV if the budget is tight.
- New build with no room for supply ducts: cMEV, ideally with real demand control.
- Renovation: cMEV or MVHR, depending on how airtight the house ends up and where ducts can run. Easiest while the house is empty, but possible while you live in it.
- One damp room in a lived-in house: a good extract fan.
- Old single-glazed windows that stream with water: ventilation helps the air and the walls, but it cannot keep cold glass dry. The windows come first.
Not sure? Send us your house plans and we will tell you which system fits and what it costs: price calculator.
Parts of a mechanical ventilation system
- Air valves: supply valves in habitable rooms, extract valves in wet rooms, set during commissioning.
- Ducts: rigid or semi-rigid pipes from the unit to each valve.
- Filters: coarse (G4) to fine (F7, catches most pollen). Newer labels use ISO 16890 (ISO Coarse, ePM10, ePM1).
- Heat exchanger and condensate drain (MVHR): the drain needs a fall and a waterless trap.
- Boost and summer bypass: boost raises the airflow for cooking or showers; the bypass lets cool night air in without warming it.
- Controls: a wall controller, sensors or the manufacturer’s app.
Frequently asked questions
What is the best ventilation system for an Irish home?
In our view, MVHR: the most comfort, the lowest heat loss and filtered air. cMEV is the budget option. Both meet Part F when designed and commissioned properly.
Is natural ventilation still allowed in new homes?
Only where the house tests between 3 and 5 m³/(h·m²). Most new builds are tighter and need a mechanical system.
What is the difference between MEV, cMEV and DCV?
MEV and cMEV are the same: a fan in a casing with a control board and a humidity sensor, extracting from every wet room all the time. Manufacturers simply label it differently. DCV is the same unit made smarter: sensors in the rooms (humidity or CO₂), more control (a controller with several modes, an app) and, at its best, zones and fresh-air vents that work with the system. It moves only as much air as the house needs, so less cold air comes in during winter.
How much does a home ventilation system cost in Ireland?
cMEV costs about €2,200–3,000 installed (zoned systems about €4,200–4,800). MVHR starts at €6,200 including VAT and is priced by floor area.
Do I need trickle vents?
With cMEV, yes: 2,500 mm² in each room apart from the wet rooms. With MVHR, no.
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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