MVHR filters should be checked every three to six months for signs that they need replacing. There are two in each unit, one filtering the air being extracted from the house which is normally a G4 filter, and the other filtering all of the air coming into the home, which is an F7 filter (a higher grade for better protection). The unit should be switched off when the filters are checked to make sure that no dust gets into the fans.
On the intake and exhaust grilles it’s likely that small insects, carbon dust, pollen and airborne particulates will have turned the filter dark grey or black. For the filter that’s protecting the home, the filter may be grey from dust that’s been picked up from inside the home.
Here’s a PAUL Novus filter after three months in a Central London home:
If the filters look relatively clean they can be cleaned carefully with a vacuum cleaner in the first instance to prolong their lifespan. If they’re dark grey or black you should contact Enhabit for a new set of MVHR filters. Filters that are close to the end of their lifespan will cause the fans to work harder and this can result in increased noise levels, poorer air quality and insufficient air supply – which can lead to mould or toxic air.
Zehnder ComfoAir Q (350, 450 and 600 ranges) and PAUL Novus MVHR (300 and 450 ranges) units will alert occupants when the filters need to be changed – normally after 180 days, but it’s good practice to check the filters every three months.
PAUL Novus unit
NOx filtration requires a separate filter box on the supply ducting to the home. A small panel on the front of the unit will indicate whether the filter requires replacing – normally after five to ten years. Replacement filters for NOx systems are also available from Enhabit.
Brink, Nuaire, Swegon and Vent Axia all have bespoke filtering systems – contact us at email@example.com to order replacement units from these brands.