The short answer is every 6 to 12 months. But that is a range for a reason — the right interval for your home depends on where you live, the season, and how the house is used. Here is how to judge it, how to tell when a filter is overdue, and why leaving it too long costs you more than the price of a filter.
The quick answer
For most homes, replace the supply and extract filters together every 6 to 12 months, and give them a quick visual check every three months. If you want a simple rule: check at the change of each season, and replace at least once a year even if the filters look only lightly loaded — filter media loses efficiency over time regardless of how dirty it looks.
What changes how often you need to
- Where you live. Beside a busy road, in a city, or near farmland at harvest, the supply filter loads up faster.
- Pollen season. Hay fever sufferers often change the supply filter more frequently through spring and summer.
- Building work. Renovation or nearby construction throws out dust that clogs filters quickly — check monthly during works, and fit fresh filters afterwards.
- How the home is used. More occupants, pets and heavy cooking all add load, mostly on the extract side.
How to tell a filter is overdue
- The supply filter is visibly grey, darkened or clogged when you pull it.
- Airflow from the supply vents feels weaker than usual.
- The unit's boost or higher speeds seem to run more, or it gets noisier, as the fans work against the resistance.
- Any filter-change indicator or alarm on the unit has tripped — many MVHR units have one.
Why overdue filters cost you
A clogged filter is not a cosmetic problem. As it loads, it restricts airflow, which drags down the heat-recovery efficiency you bought the system for and forces the fans to draw more power — so your energy bill creeps up while your air quality drops. In the worst case, reduced airflow undermines the ventilation the house needs to control moisture and condensation. We go into the efficiency and cost side in MVHR Efficiency Explained and MVHR System Running Costs.
Don't clean and reuse them
MVHR filters are designed to be replaced, not washed or vacuumed. Cleaning damages the filter media and destroys its rated efficiency, so a “cleaned” filter no longer does its job even though it is back in the unit. Replacement is the only correct maintenance.
Make it a routine
The easiest way to stay on top of it is to set a recurring reminder — a calendar entry every six months, or tied to the clocks changing — and keep a spare set in the cupboard so a change never waits on an order. Filters are one part of the wider service routine covered in our ventilation system maintenance guide.
Order genuine filters for your unit
Fit genuine filters at the correct grade so airflow and efficiency return to spec. Browse our ranges:
Not sure which you need? See How to Find the Right Replacement MVHR Filter, or send us your unit model.
Related guides
- How to Find the Right Replacement MVHR Filter for Your Unit
- MVHR Filter Grades Explained: ISO 16890, G4, M5 and F7
- Ventilation System Maintenance: Best Practices for Healthy Air
Frequently asked questions
How often should MVHR filters be changed?
Every 6 to 12 months for most homes, with a visual check every three months. Change more often in high-pollen or high-pollution areas, or during building work.
Can I just clean my MVHR filters instead of replacing them?
No. They are designed to be replaced. Vacuuming or washing damages the media and destroys the rated efficiency.
Do the supply and extract filters wear out at the same rate?
Not exactly — the supply filter usually loads faster with outdoor pollen and pollution — but it is simplest and best to change both together.
What happens if I never change them?
Airflow drops, heat-recovery efficiency falls, the fans use more power, and ventilation suffers, which can lead to condensation and poor air quality. Filters are the cheapest part of the system to maintain.