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PIV vs MVHR
PIV and MVHR are the two whole-home ventilation systems people most often confuse, but they are very different. MVHR is a balanced, ducted system that recovers heat and suits airtight homes. PIV is a single loft unit that pushes fresh air in and suits leakier, existing homes, often to tackle condensation. This guide sets out the difference and which suits which home.
By VentRight Editorial · Last updated 2026-07-08 · Impartial · Sourced
PIV pushes filtered fresh air in from a loft unit, driving stale air out through gaps. It suits leakier existing homes and has no heat recovery.
How positive input ventilation (PIV) works — labels
- unitLoft unit — A single unit in the loft filters and gently pushes fresh air into the home.
- pressurePositive pressure — The incoming air slightly raises the pressure inside the home.
- outOut through gaps — That positive pressure drives stale, damp air out through gaps in the building, such as around windows and doors.
What is the difference between PIV and MVHR?
MVHR extracts stale air and supplies fresh air through separate ducts, passing both through a heat exchanger to recover heat. PIV only supplies air: a loft unit pushes filtered fresh air into the home, raising the pressure slightly so stale air escapes through gaps. MVHR recovers heat and needs an airtight home; PIV has no heat recovery and needs a leakier one.
The two are aimed at opposite kinds of home. MVHR is a balanced system, meaning it moves equal amounts of air in and out through ducts, which is what makes heat recovery possible. PIV is single-direction: it only pushes air in and relies on the building leaking to let air out. That single difference explains almost everything else about where each one fits.
When is PIV the better choice?
PIV suits existing, leakier homes, especially where condensation or damp is the main problem. It is low cost, simple to fit in a day, and works by keeping fresh air moving through the home. Because it relies on stale air escaping through gaps, it is well matched to older housing stock that has not been made airtight.
PIV is often recommended as a targeted condensation fix rather than a whole-home upgrade. For a homeowner with a damp problem in an older house, it is a cheap and effective option. Its limitation is exactly what makes it cheap: no heat recovery and no extraction at source, which is fine in the homes it is designed for.
When is MVHR the better choice?
MVHR suits airtight homes: new builds and deep retrofits. At that airtightness there is nowhere for PIV to push stale air out to, and MVHR balanced supply and extract, plus its heat recovery, is what keeps an airtight home fresh without wasting heat. If a home is, or is becoming, airtight, MVHR rather than PIV is the appropriate system.
In an airtight home PIV would simply pressurise the house with nowhere for the air to go, while wasting the heat. MVHR is the system designed for that situation. It costs more and needs ducting, but it is doing a fundamentally bigger job: whole-home balanced ventilation with heat recovery.
Can PIV do the same job as MVHR?
No, not in an airtight home. PIV cannot recover heat and does not extract at source, so it cannot meet the same standards as MVHR where the home is sealed. In a leaky home they aim at different goals: PIV manages condensation cheaply, while MVHR is hard to justify. They are tools for different homes, not interchangeable.
It is worth being clear on this because the two are so often confused. Treating PIV as a cheap MVHR leads to disappointment in an airtight home, and treating MVHR as necessary in a leaky one leads to overspending. Match the system to the home rather than assuming one is simply better.
How much do PIV and MVHR cost?
PIV is much cheaper, often a few hundred pounds installed, because it is a single loft unit with no ducting. MVHR is a whole-house system, typically £3,000 to £10,000 installed. The price gap reflects what they do: PIV is a targeted low-cost fix, while MVHR is a whole-home ventilation and heat-recovery system.
The running costs differ too, though both are modest. PIV runs a single low-powered fan; MVHR runs balanced supply and extract fans continuously. Our cost and running cost guides break down the numbers for MVHR; PIV sits well below it on both counts.
Questions
- Is PIV as good as MVHR?
- Not in an airtight home, where PIV cannot work properly and MVHR is needed. In a leakier existing home they do different jobs: PIV is a low-cost condensation fix, MVHR is a whole-home heat-recovery system. Match the system to the home.
- Can I use PIV in a new build?
- No. A new build is airtight, so there is nowhere for PIV to push stale air out to, and it recovers no heat. New builds use MVHR or continuous extract instead.
- Does PIV have heat recovery?
- No. PIV pushes filtered fresh air in but does not recover heat from the air it displaces. Some units include a small heater, but that is not the same as the heat recovery in an MVHR system.
- Which is cheaper, PIV or MVHR?
- PIV, by a wide margin. It is often a few hundred pounds installed against roughly £3,000 to £10,000 for a whole-house MVHR system, because PIV is a single loft unit with no ducting.
PIV and MVHR side by side
| Attribute | PIV | MVHR |
|---|---|---|
| Heat recovery | No | Yes |
| Extracts stale air | No, dilutes and displaces it | Yes, from wet rooms |
| Ducting | Single loft inlet | Full supply and extract ducting |
| Best suited to | Leakier existing homes, condensation | Airtight new builds and deep retrofits |
| Typical installed cost | A few hundred pounds | 3,000 to 10,000 pounds |