Published · Updated · By the MVHR Expert engineering team
MVHR should prevent condensation, not cause it
A working MVHR system removes moist air from kitchens and bathrooms and replaces it with drier, filtered air. When condensation and mould appear anyway, it is a sign that something has stopped the system doing its job.
Common causes
- Filters blocked so airflow is much lower than design
- System switched off or turned to its lowest setting
- Valves closed, painted over or blocked by furniture or curtains
- Extract and supply not balanced, so some rooms get little air
- Failed or slow fan
- Ducts disconnected, crushed or leaking in the ceiling void
- Very high moisture sources, such as drying laundry indoors
Quick checks you can do
- Make sure the unit is on and running at its normal setting.
- Check the filter warning light.
- Hold a tissue near the extract valves in the kitchen and bathroom — it should be pulled towards the valve.
- Make sure the valves are open and clear.
- If in doubt, book a service with airflow measurement.
Cleaning the mould
Treat existing mould with an appropriate anti-mould cleaner and fix the cause as well. Mould will return if the underlying ventilation problem is not solved.