MVHR installation is more design than labour. A good installer spends as much time on the duct schematic and pressure-drop calculations as on the physical fit. The job runs in five stages: survey, design, first fix, second fix and commissioning.
1. Survey and design
The installer measures every room, identifies supply rooms (bedrooms, living areas) and extract rooms (kitchen, bathrooms), and produces a duct schematic with airflow rates per room; required for Part F compliance.
2. First fix; duct routing
Semi-rigid radial ducts (75mm or 90mm) run from a central manifold to each room. In a retrofit these go through ceiling voids, boxed in soffits, or up service risers. Insulated rigid duct connects the MVHR unit to the external wall.
3. Unit placement
The MVHR unit sits in a utility room, plant cupboard or loft. Loft installs need an insulated, accessible enclosure and condensate drain to plumbing; not just left in a cold loft.
4. Second fix; valves and trims
Ceiling valves are fitted in each room. Supply valves diffuse air gently; extract valves are higher-velocity. The unit is wired in, condensate drain tested, and external grilles fitted to the wall.
5. Commissioning and balancing
Each valve is adjusted with an anemometer until measured airflow matches the design within 10%. A commissioning certificate is issued; keep it for warranty and Building Control sign-off.
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Get matched quotesFrequently asked questions
Can I install MVHR myself?+
The unit itself can be hung by a competent DIYer, but commissioning needs calibrated anemometers and Part F sign-off. Most installers won't certify a system they didn't fit.
How noisy is MVHR?+
Properly designed, it's near silent; 25–30 dB(A) in the room. Noise complaints almost always trace to undersized ducts or missing attenuators.
What goes wrong with MVHR?+
Blocked filters (annual change), unbalanced systems (re-commission every 5 years), and condensate drain blockages in loft installs.