F7 or F9 for heat-recovery ventilation? Compare filtration, pressure drop, noise and energy use, and check the operating limits of your installation.
An F9 filter requires a heat-recovery unit that permits its use and an installation with sufficient pressure reserve at the required airflow. Approval for the unit does not remove the additional resistance: particularly in systems already close to their limit, changing from F7 to F9 can increase noise and power consumption, reduce airflow and bring forward filter replacement. Assess the complete system.
Heat-recovery ventilation units are designed to operate across a range of airflows and pressures. Their actual operating point depends on the ducts, terminals and system settings. A correctly sized compatible filter with specifications suitable for the unit does not damage it simply because it is not an original part. Dimensions, sealing, filtration class and airflow resistance all matter. Maintenance makes the difference: a heavily loaded filter increases resistance and may reduce airflow or make the fans work harder to maintain it. Regular replacement helps keep the system working properly.
F7 and F9 originate from the former EN 779 standard. ISO 16890 classifies filters by particle-fraction efficiency: PM1, PM2.5 and PM10. Eurovent’s filter-selection guidance focuses on the required protection against outdoor pollutants.
These standards use different tests, so there is no universal conversion. To compare two replacements, read each product’s ISO rating and technical data.
| Item | Check for both filters |
|---|---|
| Efficiency | Declared ISO 16890 class and percentage; F7 or F9 alone is not the full specification. |
| Airflow resistance | Pressure drop in Pa at the same airflow in m³/h, dimensions and test conditions. |
| Compatibility | Complete unit model, width, height, thickness, sealing and permitted class. |
| Appearance | A photograph cannot demonstrate filtration class or efficiency. |
The unit manufacturer must permit F9 for the specific model. Physical fit is not sufficient: check the requested airflow, available fan pressure and the resistance of the entire installation.
With comparable dimensions, construction and airflow, moving from F7 to F9 generally increases airflow resistance. This still matters when the unit accepts F9. Media, filtering area and pleat geometry can change the outcome; quantify it using data for the actual filters at the same airflow.
If the system already operates near the unit’s pressure or airflow limit, a more resistant filter can use up the remaining reserve. Long or narrow ducts, numerous bends, restrictive terminals and poor balancing make the check more important.
Have actual airflow, balancing, noise and electrical consumption checked before and after changing class. The relevant comparison is the real operating point, not simply the unit’s maximum stated airflow.
Keep the examples separate: the Siber DF EVO 2 technical page lists an F9 accessory. The consulted Brink Renovent Sky 300 manual lists G4 and F7 replacements and shows acoustic and electrical performance at different airflows and pressures. Do not transfer an F9 approval from one family or variant to another.
The ASHRAE filtration FAQ, written in the COVID-19 context and mainly discussing MERV, highlights system capability: increased resistance may reduce airflow or increase fan energy. It is not a blanket approval of F9 for residential MVHR units.
Use the filter data sheet and ventilation-unit documentation to check pressure drop and limits. Consult a technician before upgrading an F7-based system if the reserve is uncertain. Even when keeping the specified class, follow the equipment instructions. A well-seated filter and sound seals matter: gaps allow unfiltered air to bypass the media.
Our product sheets state the particular filter rating, such as ePM1 60% (F7). Some kits combine two classes, for example F7 + G4; check the pack composition before ordering and search the catalogue by exact model.
Find the filter code or the unit’s full model designation. If necessary, measure the existing element in three dimensions, then compare its class with the unit’s requirements.
There is no interval suitable for all installations: filter type, outdoor air and operating conditions determine how quickly it loads. When to replace ventilation filters. For unusual dimensions or equipment, ask about Custom-made ventilation filters. Seek technical help if safe filter access is uncertain.
Our aim is to offer European-quality compatible filters, effective filtration and good value. At ZenAero, the value of a replacement lies in its materials, careful assembly and suitability for the ventilation system.
The ePM1 60% declaration describes efficiency against PM1 particles under ISO 16890; it does not mean that every particle or allergen is removed. Choose the set specified for your model and maintain it according to the unit’s instructions.
Examples of sets containing an F7 filter from the ZenAero catalogue. These are F7 + G4 sets, not F9 filters. The Siber DF EVO set measures 139 × 175 × 48 mm; the Aerauliqa QR180/QR230E set measures 200 × 200 × 46 mm. They are not interchangeable.
Available in selected options
Price range: 24.95 € through 84.95 €
Available in selected options
Price range: 22.45 € through 76.95 €Search the ZenAero catalogue by make and model and read each product’s declared rating. If your dimensions are absent, request a custom-filter quotation. Check the current product page for availability and pricing, and contact us if you need help assessing F7 versus F9 for your unit.
They are former EN 779 classes with different efficiency requirements. Compare the specific products’ ISO 16890 declarations for PM1 and PM2.5 performance. Airflow resistance needs a separate comparison at the same airflow.
Only if F9 is permitted for your exact unit and the installation retains adequate pressure reserve at the required airflow. Even an approved F9 can increase noise and energy use or reduce airflow near the system limit. Check dimensions, pressure drop, the fan curve and actual performance after fitting.
Pleated and pocket filters used in residential ventilation are generally not designed for washing. Follow the filter and unit manufacturers’ instructions for that particular element.
Read the markings on the filter and the unit’s technical sheet. If they are missing, record the unit model and measurements and ask us to help identify the compatible replacement.
All trademarks belong to their respective owners and are used only to identify equipment and replacement compatibility. ZenAero compatible filters are not original parts from the ventilation-unit manufacturer. Before ordering, check the full model, dimensions and product specifications.
