Mechanical ventilation with heat recovery (MVHR)
Plain English. Practical detail. UK context.
MVHR is a ventilation system which extracts stale air and supplies fresh air through a heat exchanger. It recovers some heat from the outgoing air without simply recirculating the extracted air into living rooms.
Last reviewed: (editorial review against the public sources listed below).
What it means in practice
Coordinate airflow design, duct routes, terminals, noise control, condensate and maintenance access early. A unit selected in isolation does not establish the performance of the installed system. Duct resistance, leakage and commissioning affect what reaches each room.
Keep air paths and external terminals in mind during other work. Blocked ducts or changes made after commissioning can alter the intended balance. Record settings and access arrangements at handover.
For homeowners
Ask where filters are accessed, how they are maintained and how the controls should be used. The system is not air conditioning and is not a guarantee against every condensation problem. Good installation, operation and the wider building fabric all matter. Tell the designer about noise sensitivity and any planned changes to room layouts.
Practical checks
Request commissioning records and a practical demonstration. Keep maintenance instructions somewhere accessible rather than leaving them above a ceiling or inside a closed plant cupboard.
Commissioning the installed air paths
A fan unit can run while the system delivers the wrong flows to rooms. Duct resistance, crushed flexible connections, dirty filters and poorly positioned terminals can all affect operation. The installer should measure and record appropriate airflow settings and verify controls rather than copy a nominal fan speed from another house. Intake and exhaust positions must suit the building and avoid unsuitable interactions. Noise control matters at design stage: a system which occupants switch off because of noise will not operate as intended. Trainees need to understand supply, extract and transfer paths together, including what happens when doors are closed and filters accumulate normal use-related dirt.
Building guidance and operation
Approved Document F provides England's ventilation guidance, with project-specific editions and national differences to check. A retrofit must consider the existing envelope, airtightness and any combustion appliances, rather than assume adding heat recovery is automatically appropriate. Heat recovery does not provide the same service as active cooling or remove every moisture source. Explain boost settings, normal continuous operation where intended, filter access and any summer bypass function for the actual product. Keep commissioning records and maintenance instructions. A filter reminder is useful only if the homeowner can obtain the right filters and reach them safely; access should not require dismantling finished ceilings.
Frequently asked questions
Does MVHR replace a heating system?
No. It reduces some ventilation heat loss while supplying fresh air, but it is not normally the building’s main heating system. Heating and ventilation still need coordinated design.
Can I close vents in rooms that feel draughty?
Do not alter a commissioned arrangement without assessment. Report the comfort issue so flows, temperature and terminal positions can be checked without upsetting the whole system.
Sources and further reading
Public sources and further reading. Sources checked: 8 November 2026. Consult the original for details and later changes.