Home Ventilation Systems Compared
MVHR, PIV, and extract-only fans compared. Which system suits your home and budget.
Three main types of whole-house ventilation: MVHR (extracts stale air, supplies fresh air, recovers 85-95% heat), PIV (pushes fresh air from loft, relies on natural leakage for extract), and extract-only fans (removes moist air from kitchens/bathrooms only). MVHR suits airtight new builds (cost: £4,000-£8,000). PIV suits older leaky homes (£800-£1,500). Extract-only adequate for homes with trickle vents (£100-£300 per room). Choice depends on airtightness, insulation level, and whether building new or retrofitting.
MVHR (Mechanical Ventilation with Heat Recovery)
MVHR extracts stale, moist air from kitchens and bathrooms, and supplies fresh, filtered air to living rooms and bedrooms. The two airstreams pass through a heat exchanger, transferring 85-95% of heat from outgoing to incoming air without mixing the streams.1
Best for airtight homes (air permeability below 3 m³/h/m² @ 50Pa). In leaky homes, MVHR cannot control airflow effectively because uncontrolled leakage short-circuits the system.
Pros: excellent heat recovery, continuous fresh air supply, low humidity, very low running cost (£30-£50/year).2
Cons: high upfront cost (£4,000-£8,000 installed), requires ductwork throughout the house (only practical when building new or doing deep retrofit), needs filter changes every 6-12 months.
PIV (Positive Input Ventilation)
PIV units sit in the loft and push filtered fresh air into the house via a ceiling diffuser (usually on the landing). The incoming air creates slight positive pressure, forcing stale air out through natural leakage points (gaps around windows, doors, vents).
Works best in older homes with moderate air leakage. In very airtight homes, PIV has nowhere to push stale air, causing over-pressurisation and condensation risk.
Pros: low cost (£800-£1,500 installed), simple retrofit (no whole-house ductwork), effective for diluting humidity and removing condensation in leaky homes.
Cons: no heat recovery (incoming air is cold in winter, raising heating demand), less effective in airtight homes, can cause draughts if airflow is too high.3
Extract-Only Fans
Extractor fans in kitchens and bathrooms remove moist air. Fresh air enters passively through trickle vents in windows or wall vents. This is the minimum required by Building Regulations Part F 2021 for most homes.
Adequate for homes with moderate moisture levels and where occupants use extractor fans correctly. Less effective if people forget to turn fans on or close trickle vents.
Pros: low cost (£100-£300 per room), simple, meets Building Regs minimum.
Cons: no heat recovery, relies on occupant behaviour, does not supply fresh air to bedrooms (unless windows/vents are open).
Which System for Which House?
- Airtight new build or deep retrofit: MVHR. Only practical option when air permeability is below 3 m³/h/m² @ 50Pa.
- Older home with natural leakage: PIV or extract-only. PIV if condensation is a persistent problem. Extract-only if moisture levels are manageable.
- Moderate retrofit (new windows, some insulation): Extract-only fans plus trickle vents. Upgrade to MVHR if doing whole-house refurbishment.
- Budget-constrained: Extract-only fans. Upgrade to continuous-run fans with humidity sensors for better performance without major cost increase.
- MVHR Cost
- £4,000-£8,000 installed (3-bed home)
- PIV Cost
- £800-£1,500 installed
- Extract-Only Cost
- £100-£300 per room
- MVHR Heat Recovery
- 85-95% (depends on unit quality)
Sources
- Energy Saving Trust, Domestic Ventilation Systems: Comparison and Selection, 2025. energysavingtrust.org.uk (accessed 20 May 2026)
- Chartered Institution of Building Services Engineers (CIBSE), Domestic Ventilation Compliance Guide, 2022. cibse.org (accessed 20 May 2026)
- Building Research Establishment (BRE), Ventilation Strategies for Existing Homes, BRE Information Paper IP 1/23, 2023. bregroup.com (accessed 20 May 2026)
Last reviewed: 20 May 2026 | Word count: 687 | Reading time: 4 minutes