Zehnder MVHR Units

Frequently asked questions

What Zehnder MVHR units do you stock?

We stock Zehnder ComfoAir units covering airflow rates from 285 m³/h to 600 m³/h. The ComfoAir 155 WM and ComfoAir 185 WM are wall-mounted heat recovery units designed for apartments and smaller homes, delivering up to 285 m³/h with 92–93% heat recovery efficiency. For larger properties, the ComfoAir Q350 (350 m³/h), Q450 (450 m³/h) and Q600 (600 m³/h) are ceiling- or floor-mounted units with app-based speed control. We also carry the ComfoSense C 67 controller.

What is the difference between the Zehnder ComfoAir Q350, Q450 and Q600?

The three units share the same ComfoAir Q-series platform but differ in maximum airflow rate, heat recovery efficiency and duct size. The Q350 delivers up to 350 m³/h at 94% thermal efficiency with 160–190mm duct connections, suiting properties up to around 250m². The Q450 delivers up to 450 m³/h at 93% efficiency with 180–200mm connections for larger homes. The Q600 delivers up to 600 m³/h at 90% efficiency, also on 180–200mm connections, and is suited to large detached houses or light commercial spaces. All three use EC motors, support left or right hand installation, app-based speed control via Modbus, and are Passivhaus Institute (PHI) certified. All Q-series units include an integrated heating element for frost protection.

What airflow rates do Zehnder ComfoAir units deliver?

The wall-mounted ComfoAir 155 WM and 185 WM both deliver up to 285 m³/h, sufficient for a typical 2–3 bedroom flat or house. The ComfoAir Q350 delivers 350 m³/h, the Q450 delivers 450 m³/h, and the ComfoAir Q600 delivers up to 600 m³/h. Zehnder rates these at standard duct pressure drops, so real-world performance depends on your ductwork layout.

How often should Zehnder MVHR filters be replaced?

MVHR filters need regular replacement to maintain airflow and indoor air quality, the frequency depends on local air quality and the environment around the property. The Q-series units use ISO Coarse grade filters as standard with 65% filtration efficiency. We don't currently stock Zehnder replacement filters, but you can order them directly from Zehnder or contact us on 0161 399 3825 and we'll point you in the right direction. If you need filters for other MVHR brands we stock, use our Filter Finder tool.

Are Zehnder MVHR units suitable for new builds and retrofits?

Zehnder ComfoAir units are used in both new build and retrofit projects. In new builds, the ducted Q-series (Q350, Q450, Q600) are typically specified at design stage and installed with rigid or semi-rigid ducting in the ceiling void, they can be floor, wall or ceiling mounted with left or right orientation. For retrofits or smaller properties, the wall-mounted ComfoAir 155 WM and 185 WM offer a more compact installation, designed for wall or cupboard mounting in properties up to around 125m². All units meet the ventilation requirements of Building Regulations Part F and contribute to SAP compliance under Part L, making them a solid choice for achieving energy efficiency targets on any project type.

What makes Zehnder different from other MVHR brands?

Zehnder was founded in Switzerland in 1912 and has over a century of experience in indoor climate solutions. They hold more than 1,400 global patents and registered designs, and operate in over 70 countries. The ComfoAir Q-series units are certified by the Passivhaus Institute (PHI), meaning they have been independently tested and verified for airtightness, heat recovery efficiency, and low electrical consumption. All Q-series units use cross-counter-flow heat exchangers and EC motors for high efficiency at low power consumption, with thermal efficiencies ranging from 90% (Q600) to 94% (Q350) at 70% airflow. The Q-series accepts duct connections from 160mm to 200mm depending on the model.