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In winter, outdoor air becomes very dry once it is heated indoors, and mechanical ventilation often reduces indoor relative humidity to 20–30 RH or even lower. This article explains why this happens, how different heat exchanger types (plate, condensation rotor, enthalpy, sorption) affect indoor moisture balance, and what you can do in practice. We cover smart ventilation control during cold nights, protection against excessive drying, when a humidifier is really needed, and simple ways to increase or reduce humidity naturally. You will also find an FAQ with common real-life situations and climate-specific recommendations for different countries.
Cold outdoor air and warm, humid extract air can create condensation that may freeze inside the heat exchanger. Learn what “defrost” does, why airflow balance matters, and how to reduce frequent frost cycles.
Not all ventilation unit filters are the same. Some ensure clean, healthy indoor air, while cheaper or uncertified filters can pose risks to both the ventilation system and your health. This guide explains what to look for when choosing filters — from ISO 16890 testing and hygiene standards to material safety and real filtration performance — so you can be confident you’re using a safe, certified and reliable filter.
Advanced Filters for Zehnder ComfoWell CW 320, Zehnder ComfoWell CW 625 filter box
Elevate your indoor air quality with our top-tier analog Zehnder filters, designed for perfect compatibility with ComfoWell CW 320 / CW 625 filter box. These filters optimize performance and provide robust protection against pollutants.
ComfoWell CW 320 / CW 625 filter dimensions: 300x225x48, 300x225x96 mm.
Available options:
- Filter set: F7, ePM1 70% / Filter F7/AC, activated carbon.
Our panel Zehnder filters rigorously adhere to ISO 16890 standards, with exceptional filtration efficiency confirmed by FIATEC lab tests in Germany. Crafted from EU-sourced high-quality materials, our innovative 3-layer filtration material ensures optimal performance.
Benefits:
- Low prices.
- Tested efficiency
- Extended filter lifespan.
Includes a 2-year storage guarantee. Trust in our EU-manufactured filter excellence.
There are 2 products.
Ex VAT: £8.88
| Manufacturer of MVHR | Zehnder |
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Filter dimensions | 300x225x48 |
| Class EN779 | F7 |
| Class ISO16890 | ePM1 70% |
| Protection level | High: fine particles, dust, pollen, mold spores, combustion particles, smog particles, insecticide dust. |
| Quantity of filters | 1 |
| Advantages |
|
| Manufacturer product number |
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Ex VAT: £23.93
| Manufacturer of MVHR | Zehnder |
| Manufacturer | CleanFilter |
| Air handling unit |
|
| Filter dimensions | 300x225x96 |
| Class EN779 | F7/AC |
| Class ISO16890 | ePM2.5 60% |
| Protection level | Particles and odors: fine particles, dust, pollen, mold spores, combustion particles, volatile particles, NOx, O3 gases. |
| Quantity of filters | 1 |
| Advantages |
|
| Manufacturer product number |
|
