MVHR vs MEV: Balanced Heat Recovery or Continuous Extract
MVHR (Mechanical Ventilation with Heat Recovery) vs MEV (Mechanical Extract Ventilation).
Reviewed by George Sora, Certified Passive House DesignerUpdated June 2026Quick answer & key takeaways
5 min read- Bottom line: MVHR is a balanced supply-and-extract system that recovers heat and filters incoming air; MEV is extract-only and relies on uncontrolled inlets to make up the air.
- When MVHR is enough: The home is, or will be, airtight (broadly below 3 ach@50)
- When MEV is the better choice: The fabric remains relatively leaky
- When you need both: You are unsure of airtightness — test first, then let the result decide
- Biggest misconception: “MEV is just a cheaper MVHR.” — They are different strategies. MEV recovers no heat and does not condition or filter supply air; MVHR is balanced and heat-recovering.
- Retrofit IQ’s approach: We never specify a ventilation system from a brochure.
Quick answer
MVHR is a balanced supply-and-extract system that recovers heat and filters incoming air; MEV is extract-only and relies on uncontrolled inlets to make up the air. In an airtight, well-insulated home MVHR is the correct choice because it ventilates fully while saving the ventilation heat. MEV suits leakier homes, or where ducting a full supply network is impractical, and is a step up from intermittent fans — but it loses heat and cannot filter supply air.
At a glance
| Attribute | MVHR (Mechanical Ventilation with Heat Recovery) | MEV (Mechanical Extract Ventilation) |
|---|---|---|
| Principle | Balanced supply + extract with heat recovery | Continuous extract; passive make-up air |
| Heat recovery | Yes — 80–92% typical | No |
| Filtered supply air | Yes (G4/F7/ISO ePM1) | No — air enters via vents/gaps |
| Airtightness needed | Yes — ideally below ~3 ach@50 | Tolerant of leakier fabric |
| Ductwork | Supply + extract network | Extract ducts only |
| Install cost | Higher | Lower |
| Winter heat loss | Low (recovered) | Higher (extracted heat lost) |
| Best suited to | Deep retrofit, EnerPHit, new build | Mid-level retrofit, flats, moisture control |
What is MVHR (Mechanical Ventilation with Heat Recovery)?
A balanced, ducted system that supplies filtered fresh air to habitable rooms and extracts stale, moist air from wet rooms, passing both airstreams through a counter-flow heat exchanger to recover 80–92% of the heat that would otherwise be thrown away. It is the ventilation strategy assumed by Passive House and EnerPHit, and depends on the building being airtight.
What is MEV (Mechanical Extract Ventilation)?
A continuously running central or decentralised extract system that pulls air only from wet rooms (kitchen, bathrooms, utility), with fresh air entering through background ventilators (trickle vents) and infiltration. It is simpler and cheaper to install than MVHR, but recovers no heat and offers no filtered supply.
What each method measures — and what it doesn’t
MVHR
- Balanced supply and extract flow rates, commissioned room by room to design figures (l/s)
- Heat-recovery efficiency across the exchanger, verified at commissioning
- Filtration quality on supply air (pollen, particulates, ISO ePM1 fractions)
- Nothing — but it only performs as designed if the envelope is airtight and the ducts are commissioned
MEV
- Extract flow rates from wet rooms against Building Regulations minima
- Continuous background air exchange to control humidity
- It does not recover heat, so it cannot quantify or reduce ventilation heat loss
- It does not control or filter where make-up air enters from
The building science
Ventilation removes water vapour, carbon dioxide and pollutants and brings in oxygen. The thermodynamic catch is that any air you exhaust in winter leaves at room temperature and is replaced by air at outdoor temperature, so ventilation heat loss rises directly with the air-change rate. In a leaky, poorly insulated house this is hidden inside the large fabric and infiltration losses; in an airtight, well-insulated house it becomes one of the largest single heat losses, which is precisely why heat recovery matters.
MVHR addresses this by routing the warm, outgoing extract air past the cold, incoming supply air through a counter-flow or counter-flow-with-bypass exchanger, transferring sensible (and, with enthalpy cores, some latent) heat without mixing the two streams. A well-commissioned unit recovers the great majority of that heat, which is why a Passive House can ventilate continuously yet still meet a 15 kWh/m².a heating demand. The system only delivers this if the building is airtight: uncontrolled infiltration short-circuits the balanced flows, so the heat-recovery benefit collapses in a leaky house.
MEV takes the opposite, simpler route. It extracts continuously from wet rooms and lets replacement air find its own way in through trickle vents and the building's leakage. It reliably controls humidity and meets the regulatory extract rates, and runs at low fan power, but the heat in the extracted air is simply lost and the incoming air is neither tempered nor filtered. That makes MEV a sound, low-cost humidity-and-IAQ strategy for leakier homes, and a clear improvement on intermittent fans, but the wrong tool once a building is taken to genuine airtightness.
Key differences
- MVHR recovers heat and filters supply air; MEV does neither.
- MVHR is balanced (supply + extract); MEV is extract-only with passive make-up air.
- MVHR requires airtightness to work; MEV tolerates — and partly relies on — a leakier envelope.
- MVHR needs a full duct network and commissioning; MEV needs only extract ducting.
- On cost, MEV is cheaper to install; on running energy, MVHR is far cheaper in winter because the heat is kept.
Common misconceptions
Myth: MEV is just a cheaper MVHR.
They are different strategies. MEV recovers no heat and does not condition or filter supply air; MVHR is balanced and heat-recovering.
Myth: MVHR makes a home stuffy or 'sealed up'.
Correctly commissioned MVHR supplies continuous filtered fresh air, so indoor air quality is usually better than in a naturally ventilated home.
Myth: Any extract fan running continuously counts as MEV.
Proper MEV is a designed, balanced-rate system with commissioned flows and adequate background inlets, not a bathroom fan left on.
Real-world situations
Deep retrofit taken to genuine airtightness, or new build
MVHR — it is the only strategy that ventilates fully while recovering the ventilation heat, and it is what the airtightness was for.
Mid-level retrofit, flat, or where supply ducting cannot be routed
MEV — continuous extract controls moisture reliably at lower cost, provided background ventilators are sized correctly.
Persistent condensation in a leakier home on a budget
MEV (or PIV) to manage humidity, alongside warming cold surfaces; revisit MVHR if and when airtightness is improved.
Which do you actually need?
When MVHR is enough
- The home is, or will be, airtight (broadly below 3 ach@50)
- You are pursuing Passive House, EnerPHit or low running costs
- Filtered supply air matters (allergies, pollution, pollen)
When MEV is the better choice
- The fabric remains relatively leaky
- Supply ducting to every habitable room is impractical
- The priority is reliable moisture control at lower cost
When you need both
- You are unsure of airtightness — test first, then let the result decide
- A phased retrofit where MEV now may become MVHR after fabric works
What Retrofit IQ checks on site
We never specify a ventilation system from a brochure. We measure airtightness and the building's real moisture and occupancy loads first, then choose between MVHR and MEV on evidence — because fitting balanced MVHR to a leaky house wastes its main benefit, and so does ignoring moisture loads when sizing MEV.
- Blower door test to establish whether the envelope can support balanced MVHR or suits extract-only MEV
- Measured wet-room moisture loads, occupancy and CO₂ patterns to size ventilation realistically
- Duct routing feasibility, including riser and ceiling-void space and external terminal positions
- Commissioning flow rates room by room against the design schedule, not just at the unit
- Heat-recovery efficiency check and filter-access review on MVHR units
- Background ventilator sizing and positioning where MEV is specified
What a Certified Passive House Designer recommends
I choose between MVHR and MEV from the blower door result, not from a preference. Once a home is genuinely airtight, MVHR is the correct answer and must be designed and commissioned properly — duct sizing, flow balancing, filter access and a sensible terminal layout all matter as much as the unit itself.
MEV is an honest, cost-effective system for leakier homes and flats, and a real improvement on intermittent fans. The mistake to avoid is fitting MVHR to a house that has not been made airtight and then wondering why the promised efficiency never arrives.
— George Sora, Certified Passive House Designer, Founder, RetrofitIQ
Reviewed using current building physics principles and Passive House methodology.
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Continuous extract removes moisture steadily all day and responds to humidity; intermittent fans only act in short bursts when triggered, leaving long unventilated gaps.
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Natural ventilation is uncontrolled — it depends on wind, temperature and whether people open windows and vents — and it discards heat with the air.
Read comparisonFrequently asked questions
Is MVHR always better than MEV?+
Only in an airtight home. MVHR recovers heat and filters supply air, but those benefits depend on airtightness. In a leakier home MEV is often the more sensible, cost-effective choice.
Does MEV recover any heat?+
No. MEV extracts stale air and lets replacement air enter through vents and gaps, so the heat in the extracted air is lost. Only MVHR recovers it.
How airtight does a house need to be for MVHR?+
There is no hard cut-off, but the balanced flows and heat-recovery benefit hold up well below roughly 3 ach@50; above that, infiltration increasingly short-circuits the system.
Can I retrofit MVHR to an older house?+
Often yes, where ducts can be routed and airtightness improved. We assess duct feasibility and test airtightness as part of the design before recommending it.
Will MEV cause draughts in winter?+
It can if background ventilators are poorly sized or placed, because cold air enters untempered. Correct sizing and positioning of inlets minimises this.
Does either system need filter changes?+
MVHR has supply and extract filters that need periodic changing to maintain efficiency and air quality. MEV has minimal filtration. Filter access should be designed in for MVHR.
Which is quieter?+
Both can be quiet when correctly specified. MVHR noise depends on duct design and attenuation; MEV noise depends on the unit and duct runs to wet rooms.
Is MVHR worth it for moisture control alone?+
For moisture alone, MEV or PIV may be enough. MVHR earns its place when you also want heat recovery and filtered supply air in an airtight home.
Can I run MVHR without commissioning the flows?+
You should not. An uncommissioned MVHR rarely delivers its design flow rates or efficiency; commissioning room by room is what turns the hardware into a working system.
Do these systems help with a heat pump?+
Yes — MVHR in particular lowers ventilation heat loss, reducing the heat demand a heat pump must meet and helping it run efficiently at low flow temperatures.
Need professional advice?
A comparison like this helps you understand the theory, but every property behaves differently. The only reliable way to establish the real cause in your home — rather than guessing — is professional building performance diagnostics. At RetrofitIQ we verify buildings using the appropriate combination of investigations:
- Thermal imaging
- Blower door testing
- Moisture investigation
- Building physics assessment
- Passive House methodology