Last updated: January 19, 2026
Many people assume that an MVHR system is something that “just works” — you switch it on and forget about it. The reality is very different. An MVHR system is only truly beneficial when the filters are clean. Once MVHR filters become contaminated, the system not only stops protecting you from pollution, but starts working against you: the air feels heavier, odours linger for longer, and electricity consumption increases.
Let’s look at how this plays out in real-life situations — depending on property size, system type and living environment.
Example 1:
50 m² flat with a Paul Climos 200 MVHR unit
The Paul Climos 200 is an enthalpy MVHR unit supplying up to 200 m³ of air per hour, with around 84% heat recovery and humidity retention in winter. For a 50 m² flat, this is more than sufficient capacity, meaning the air should feel light, fresh and clean. The system is typically equipped with an M5 extract filter and an F7 supply filter.
- Living close to nature, filters usually last around six months, sometimes even longer. However, during pollen season in spring, the F7 filter may clog more quickly. The first signs of dirty filters are lingering cooking smells, air that feels less fresh in the morning, and a stuffy feeling in the bedroom.
- In suburban areas, the situation becomes more serious. Here, F7 filters often clog within 3–6 months. A contaminated filter can restrict airflow by 10–15%, forcing the system to work harder. It may become noisier, and you may start feeling that the air is heavier, with a growing urge to open windows more often and a sensation of not being able to breathe deeply.
- In cities, especially in Vilnius, filters clog the fastest. F7 filters often need replacing every 3 months. If you delay, airflow can drop by more than 20%, and you may begin to notice bathroom or cooking smells spreading through rooms, with air that feels stale and stagnant.
Example 2:
80 m² house with a Zehnder ComfoAir Q350
The Zehnder ComfoAir Q350 is a highly efficient unit, supplying up to 350 m³/h of air with around 90% heat recovery. In an 80 m² home, it operates quietly and efficiently, with capacity to spare. The standard setup includes G4 and F7 filters.
- Living in a natural environment, filters usually last around six months. However, if they are not replaced in time, dust begins to accumulate not only in the filters but inside the system itself. This results in reduced efficiency and increased indoor humidity, with occupants noticing a heavy feeling in the air, particularly in bedrooms.
- In suburban locations, filters typically need replacing every 4–6 months, and even sooner if there are gravel roads, construction sites or dense vegetation nearby. A clogged filter increases system resistance, leading to higher electricity consumption — often without occupants realising why.
- In urban areas, the realistic replacement interval is every 3–4 months. If you delay, you will quickly notice that odours linger, the air feels stuffy, and you increasingly want to open windows.
Example 3:
160 m² house with a Zehnder Q350
In a larger house, significantly more air passes through the filters each day. This leads to one simple outcome: filters clog faster, even if you live outside the city.
- Living in nature, filters may remain effective for around six months, but during pollen season, more frequent replacement is advisable. For allergy sufferers, runny nose, itchy eyes and breathing discomfort may appear, along with poor sleep and a feeling of air shortage.
- In suburban areas, a realistic replacement interval is 4–5 months, especially in dusty surroundings. If filters are not replaced on time, airflow drops, fan noise increases, bedrooms become stuffy, and odours linger.
- In urban environments, F7 filters in large homes often clog within 2–3 months. If left unchanged, airflow drops significantly, the MVHR unit operates under strain, and occupants begin to notice everything: bathroom and kitchen odours, heavier air, increased noise, and higher electricity bills.
If filters are not replaced on time, the MVHR system loses its purpose — instead of supplying clean air, it simply recirculates the same polluted air throughout the home.
Looking for where to buy MVHR filters? You can do so in Vilnius at Sedulų g. 2, Bukiškis, or online at “Filtrų pasaulis”.
Contact us and we’ll help you choose the right G4, M5 or F7 filters, based on your MVHR unit and living environment.
Article prepared by: Paulina Padeginskaitė
