Understanding Supply and Extract Filter Grades in Systemair MVHR Units

When ordering replacement filters for your Systemair ventilation unit, one of the most common questions we receive is:

"What filter grade do I need?"

The answer can vary depending on the model, installation requirements, and whether additional pre-filters have been fitted. Understanding the different filter grades can help ensure you maintain excellent indoor air quality while keeping your ventilation system operating efficiently.

The Difference Between Supply and Extract Filters

Most MVHR (Mechanical Ventilation with Heat Recovery) units contain two sets of filters:

Supply Air Filters

Supply filters clean the fresh outdoor air before it enters your home or building. These filters are responsible for capturing:

• Dust
• Pollen
• Fine airborne particles
• Traffic-related pollution
• Other outdoor contaminants

In many Systemair residential MVHR units, the supply filter is typically an F7 grade filter. This finer filtration helps improve indoor air quality, particularly for allergy sufferers and occupants living in urban environments.

Extract Air Filters

Extract filters protect the MVHR unit itself by removing particles from the stale air being extracted from kitchens, bathrooms, and living spaces.

In many Systemair products, the extract filter is typically an M5 grade filter. As the extract air has already entered the building, the primary purpose of this filter is to protect the heat exchanger and internal components rather than provide high-level air cleaning.

Does Your Unit Have a Pre-Filter?

Not all installations are the same.

Some systems are fitted with an additional G4 pre-filter on the fresh air intake before the air reaches the main F7 supply filter.

The purpose of a G4 pre-filter is to:

• Capture larger airborne particles
• Extend the life of the F7 filter
• Reduce maintenance costs
• Improve overall system performance

Because of this, it is important not to assume your unit only contains two filters. Some installations may have:

• F7 Supply / M5 Extract
• G4 Supply / G4 Extract
• G4 Pre-filter + F7 Supply + M5 Extract
• Alternative configurations specified by the designer or installer

Always Check Your Existing Filters

Before ordering replacement filters, we recommend checking the filters currently installed in your unit.

Look for:

• The filter grade printed on the filter frame
• Any labels showing F7, M5, G4 or ISO ePM ratings
• The quantity of filters fitted
• Whether a separate pre-filter is installed

This simple check can prevent ordering the wrong filter set and ensure your replacement matches the original specification.

The Importance of Model Information

Systemair has manufactured a wide range of ventilation products over the years, including:

• SAVE units
• Villavent units
• Topvex units
• Residential MVHR systems
• Commercial air handling units

Filter arrangements can differ significantly between models, even when they appear similar externally.

For this reason, it is always helpful to provide the model number when requesting replacement filters.

Examples include:

• SAVE VTR 150
• SAVE VTR 300
• SAVE VTR 500
• Villavent VR-series units
• Topvex units

Providing the exact model allows us to identify the correct filter grade and dimensions more quickly.

Why the Serial Number Is Even Better

The best information you can provide is the unit's serial number.

The serial number can usually be found on the unit's nameplate and allows us to verify:

• The exact unit specification
• Filter configuration
• Manufacturing details
• Any factory-fitted options
• Correct replacement filter set

This helps eliminate guesswork and ensures you receive the most suitable filters for your particular installation.

Need Help Identifying Your Filters?

At NuFilter, we are happy to help identify the correct replacement filters for your ventilation unit.

To help us provide the fastest and most accurate recommendation, please include:

✅ Unit model number
✅ Serial number (from the nameplate)
✅ Existing filter grades if visible
✅ Photos of the filters or unit, if available

The more information you can provide, the easier it is to ensure you receive the correct replacement filters first time.

Final takeaways

Many Systemair MVHR systems commonly use an F7 supply filter and an M5 extract filter, but every installation should be checked individually. Some units may also include a G4 pre-filter on the supply air side, while others may use different filter grades depending on the application.

Before ordering, always check the filters currently installed and, where possible, provide the unit model and serial number from the nameplate. This allows the NuFilter team to supply the correct filters and help maintain the highest levels of indoor air quality and system performance.

Need replacement filters? Contact the NuFilter team today with your model and serial number, and we'll help identify the correct filter set for your Systemair unit.