A heat recovery system ventilates a building while reducing the heat lost with outgoing stale air. In homes, the most common version is mechanical ventilation with heat recovery, or MVHR, which extracts humid air from kitchens, bathrooms and utility rooms while supplying filtered fresh air to living spaces and bedrooms.
MVHR can be excellent in airtight homes, deep retrofits and new builds, but it is not a magic box for every property. Duct routes, airtightness, commissioning, filter access and maintenance decide whether it feels quiet and useful or expensive and disappointing.
Contents
- 1 Key Takeaways
- 2 How Heat Recovery Ventilation Works
- 3 Types Of Domestic Heat Recovery System
- 4 When MVHR Makes Sense
- 5 When It May Not Be Worth It
- 6 Benefits And Trade-Offs
- 7 Design And Maintenance Checklist
- 8 Common Design Mistakes
- 9 Expert Insights From Our Heating Engineers
- 10 Frequently Asked Questions
- 11 Summing Up
Key Takeaways
- MVHR extracts stale air and supplies filtered fresh air continuously.
- A heat exchanger transfers warmth from outgoing air to incoming air without mixing the streams.
- It works best in airtight homes, new builds and major retrofits.
- Leaky homes may need draught-proofing or other ventilation options first.
- Filters, duct cleaning access and commissioning are essential.
How Heat Recovery Ventilation Works
In an MVHR system, extract ducts remove air from wet rooms such as bathrooms, kitchens and utility rooms. Supply ducts deliver fresh filtered air to living rooms, bedrooms and studies. Inside the unit, the outgoing warm air passes through a heat exchanger beside the incoming cold air, transferring heat without the two airstreams mixing.
The result is controlled ventilation with less heat loss than simply opening windows in winter. In summer, some units include bypass modes so the system can reduce unwanted heat recovery when conditions allow.
Types Of Domestic Heat Recovery System
| System | How It Works | Best Fit |
|---|---|---|
| Whole-house MVHR | Central unit with supply and extract ductwork | Airtight new builds and major retrofits |
| Single-room heat recovery fan | Local unit recovers some heat from one room | Bathrooms, extensions or targeted ventilation |
| Extract-only ventilation | Removes stale air without heat recovery | Less airtight homes or simpler upgrades |
| Demand-controlled ventilation | Adjusts airflow based on humidity or occupancy | Homes needing smarter ventilation without full MVHR |
MVHR is the option people usually mean when they talk about heat recovery in a whole house, but it is not the only ventilation choice. Positive input ventilation, continuous extract fans and decentralised heat recovery units can all be suitable in the right property. The best choice depends on airtightness, budget, disruption tolerance and whether you are solving heat loss, condensation, stale air or all three.
| Ventilation Choice | Strength | Limitation |
|---|---|---|
| MVHR | Balanced supply and extract with heat recovery | Needs good airtightness and duct routes |
| PIV | Can help dilute moisture and improve airflow in some homes | Does not recover heat in the same way |
| Continuous extract | Simple, familiar and often easier to retrofit | Extracts warm air without recovering much energy |
| Single-room heat recovery | Targeted solution with less disruption | Does not provide whole-house balanced ventilation |
When MVHR Makes Sense
MVHR is most convincing when the home is airtight enough for controlled ventilation to matter. In a new build, Passivhaus-style project or deep retrofit, opening holes for uncontrolled ventilation wastes the effort put into insulation and air sealing. MVHR helps maintain air quality while keeping more heat inside.
It can also help with condensation and indoor air quality because humid air is extracted continuously from wet rooms. Incoming air is filtered, which can help reduce pollen and some particulates. That does not make MVHR an air purifier replacement in every scenario, but it improves the ventilation baseline.
When It May Not Be Worth It
In a very leaky home, MVHR can underperform because air is already entering and leaving through uncontrolled gaps. The unit may still move air, but the heat recovery benefit is diluted. In that case, draught-proofing, insulation and simpler ventilation improvements may come first.
Retrofit disruption is another issue. Whole-house ductwork needs routes through ceilings, lofts, cupboards or service voids. If the home is not being renovated, the cost and disruption can be hard to justify. A single-room solution or good extract ventilation may be more realistic.
Benefits And Trade-Offs
| Benefit | Reality Check |
|---|---|
| Lower ventilation heat loss | Depends on airtightness and commissioning |
| Better air quality | Filters must be changed and ducts designed well |
| Condensation control | Moisture sources still need sensible management |
| Quiet background ventilation | Poor duct design can cause noise |
| Works well with low-carbon heating | Does not replace heating or insulation |
Design And Maintenance Checklist
- Check the home airtightness or retrofit plan before specifying MVHR.
- Plan supply and extract rooms properly.
- Keep duct runs short, insulated where needed and accessible.
- Commission airflow rates after installation, not just fit the unit.
- Choose a unit with accessible filters and sensible controls.
- Replace filters at the recommended interval.
- Keep external intake and exhaust terminals clear.
If you are improving a home for low-carbon heating, MVHR may sit alongside insulation and heating design. Our heat pumps guide and damp guide cover related decisions.
Commissioning Is Where Many Systems Win Or Fail
Once the unit is installed, each room terminal should be measured and balanced. Bathrooms need enough extract to remove moisture; bedrooms and living spaces need enough supply to feel fresh without draughts. If the installer does not record flow rates, the homeowner has little evidence that the system is actually performing as designed.
Noise is another commissioning issue. A powerful unit can still feel quiet if duct sizes, bends, silencers and fan speeds are chosen properly. A cheaper installation with tight duct runs can make bedrooms sound busy at night, which often leads users to turn the system down and lose the ventilation benefit.
Retrofit Practicalities
In a retrofit, ask where the ducts will run before agreeing to the system. Loft routes can be neat, but cold spaces need insulated ducting to reduce condensation and heat loss. Cupboards and ceiling voids may work, but access panels should be planned so filters, dampers and key junctions are not buried forever behind plasterboard.
Common Design Mistakes
The most common MVHR mistake is treating ductwork as an afterthought. Long, squeezed or badly routed ducts increase resistance and noise. Poorly positioned terminals can allow exhaust air to be drawn back into the intake. Inaccessible filters then make maintenance harder, so performance drops quietly over time.
Another mistake is assuming MVHR will fix mould by itself. If walls are cold, insulation is weak or moisture production is excessive, ventilation helps but may not solve the underlying issue. A good design considers airtightness, insulation, heating and moisture together.
New Build Example
In a new airtight home, MVHR can be planned early so ducts run cleanly through joists, cupboards or service zones. Commissioning then balances supply and extract airflow room by room, making the system quiet and effective.
Retrofit Example
In an occupied older home, duct routes may be difficult. A whole-house system can still work during major renovation, but single-room heat recovery or better extract ventilation may be more realistic if ceilings and walls are not being opened.
Maintenance is simple but important. Filters protect the heat exchanger and indoor air quality, but clogged filters increase fan energy and reduce airflow. Homeowners should know where the filters are, how to remove them, what replacement grade is required and whether the system has a service reminder. A neglected MVHR system can become noisy and ineffective even if it was well designed originally.
Commissioning paperwork is also worth keeping. It should show measured airflow rates for supply and extract terminals, not just the model number of the unit. If a room feels stuffy or a bathroom stays humid, those figures help an engineer check whether the issue is design, adjustment, blockage or user settings.
Expert Insights From Our Heating Engineers
Our engineers see MVHR succeed when it is treated as a designed ventilation system, not an accessory. The duct routes, room flow rates, noise control and commissioning matter as much as the unit brand.
The biggest mistake is fitting MVHR into a home that has not been made airtight enough, then expecting dramatic savings. Start with the fabric, decide how the home should breathe, then choose the ventilation system that matches that strategy.
We would rather see a simpler ventilation system installed well than an expensive MVHR system squeezed into a poor layout. If ducts are too long, filters are inaccessible or the intake is badly positioned, the specification may look impressive but the lived experience will disappoint.
Frequently Asked Questions
What Does MVHR Stand For?
MVHR stands for mechanical ventilation with heat recovery. It is a whole-house ventilation system that extracts stale air, supplies fresh filtered air and transfers heat from outgoing air to incoming air through a heat exchanger.
Does MVHR Heat A House?
No. MVHR reduces ventilation heat loss, but it is not a replacement for heating. It can make an efficient home easier to heat because less warmth is lost through ventilation, but you still need a proper heating system.
Is MVHR Worth It In An Older House?
It can be worth it during a deep retrofit where airtightness and duct routes are planned together. In a leaky older home with no major renovation planned, simpler ventilation, draught-proofing and insulation may be more cost-effective first.
Does MVHR Stop Condensation?
It can reduce condensation risk by continuously removing humid air from wet rooms, but it does not remove the need for heating, insulation and sensible moisture management. Persistent condensation may still point to cold surfaces or excessive moisture production.
How Often Do MVHR Filters Need Changing?
Filter intervals vary by unit, location and air quality, but many homes need checks every few months and replacement once or twice a year. Dirty filters reduce airflow, increase fan workload and can make the system noisier.
Can MVHR Work With A Heat Pump?
Yes. MVHR and heat pumps can work well together in an efficient, airtight home. MVHR reduces ventilation heat loss, while the heat pump supplies space heating and hot water. Both systems still need proper design and commissioning.
Summing Up
Heat recovery systems can improve ventilation while reducing heat loss, but they work best when matched to the building. MVHR is strongest in airtight new builds and deep retrofits; leaky homes may need fabric improvements or simpler ventilation before a whole-house heat recovery system makes sense. The decision should be based on airtightness, duct routes, commissioning quality and future maintenance access, not just the quoted heat recovery percentage or the unit brand alone on paper.
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