Ventilation & MVHR Replacement Filters

Replacement ventilation filters keep your MVHR or PIV unit working at spec — clean filters mean proper airflow, efficient heat recovery, and clean air entering the building. We stock 17 replacement filter sets for Systemair, Villavent and Vent-Axia units, covering the VR 200/250/300/400/700 MVHR range, the VX 400/500/700 extract units, the VSR 300 and VTR 200/250 heat recovery units, the VTC Low E range and the Vent-Axia Pozidry Compact PIV. All filters are in stock for next-day UK delivery. Not sure which filter fits your unit? Email hello@efans.co.uk with your unit model number or call 0161 818 2050 and we'll match it.

How often should I replace my MVHR or ventilation filter?

Manufacturer guidance for most domestic MVHR units (Systemair VR range, Vent-Axia Sentinel, Nuaire MRXBOX) is to change the filter set every 6 to 12 months, with the supply-side filter (G4 or F7 pre-filter) often needing replacement more frequently than the extract-side filter. In practice, filter life depends on local air quality — homes near main roads, farmland, building sites or in high-pollen areas typically need changes every 4–6 months; rural homes with low external dust might stretch to 12 months. Most modern MVHR units include a timer or pressure-drop sensor that triggers a filter warning light — change filters when the light comes on, don't ignore it.

Which filter fits the Vent-Axia Pozidry Compact PIV?

The Vent-Axia Pozidry Compact PIV (loft-mounted positive input ventilation unit, part 479188) uses a G4 replacement filter — our SKU 479860. It's a direct fit for the Pozidry Compact range and should be replaced every 12 months or when the unit's filter warning light illuminates. The filter sits in the unit's air intake to keep dust and insects out of the fan and the living space below.

What do the filter grades G4, F7, M5 and ePM1 mean?

Filter grades describe how efficiently the filter captures airborne particles. G4 (now classed as ISO Coarse under the EN ISO 16890 standard) is a standard pre-filter that catches dust, lint and insects — fine for PIV units and the extract side of most MVHR. F7 (now classed as ePM1 50%–80%) is a finer supply-side filter that captures pollen, fine dust and most bacteria — specified on MVHR supply filters where indoor air quality matters (new builds, Passive House, allergy sufferers). M5 (ePM10) sits between the two. Modern units increasingly quote the new EN ISO 16890 ePM1/ePM2.5/ePM10 ratings, but G4 and F7 labels are still in common use and the replacement filters we supply match whatever the original-equipment filter was rated.

Can I wash or vacuum the filter instead of replacing it?

No — don't. MVHR and PIV filters are made from a pleated fibrous media designed to be disposable. Vacuuming flattens the pleats, reduces filter surface area, and pulls the fibre structure apart, which drops efficiency and drives up fan pressure. Washing a G4 or F7 filter destroys the electrostatic charge on the fibres that captures fine particles. Always replace, don't clean. If you want a washable option, some units accept a coarse mesh pre-filter upstream of the main filter — but the main filter still needs regular replacement.

What happens if I don't change the MVHR filter?

A blocked filter increases the pressure drop across the unit, which forces the fan to work harder to maintain airflow — so energy use goes up, noise goes up, and airflow can still drop below design. Heat recovery efficiency also drops because the unit can't move enough air through the exchanger core. Worst case, a badly blocked filter can pull dust and debris through the filter housing into the heat exchanger itself, which is expensive to service. Filters are £50–£95 a set; a ruined exchanger core is hundreds. Change them.

Are these genuine Systemair or compatible filters?

Our range is a mix of genuine Systemair/Villavent parts (labelled "Genuine Part" on the product page) and compatible equivalents built to the same dimensions and filter grade as the OEM part. Compatible filters are significantly cheaper than genuine and fit the same unit models — they use the same pleated media, the same frame dimensions, and the same filter grade. Choose genuine if you want factory-branded parts for a warranty claim, choose compatible if you're changing filters on your own house and want the same performance for less. Both are stocked and both ship next day.

Do you stock filters for Envirovent, Nuaire, Zehnder or Vaillant MVHR units?

Not currently — we focus on the Systemair, Villavent and Vent-Axia brands we supply as whole MVHR units. If you've got an Envirovent, Nuaire MRXBOX, Zehnder ComfoAir, Vaillant recoVAIR or other brand and need filters, email hello@efans.co.uk with the unit model and we'll either source the filter or point you to the right supplier. We'd rather send you elsewhere than sell you the wrong part.

Can I buy individual supply or extract filters, or only sets?

Both. Most Systemair/Villavent MVHR units use a matched supply-and-extract pair, and we stock filter sets (both filters together — usually the most cost-effective option). We also stock individual supply-only or extract-only filters for units where one side fouls faster than the other: VSR 300 (supply SKU 212472 / extract SKU 212473), VX 500/700 (supply 212460 / extract 5883), and VX 400 supply (212459). If your extract filter is still clean when your supply filter is due, a single replacement saves money.