MVHR Commissioning of a Zehnder ComfoAir Q600 with ComfoCool unit completed

Today we finished the final stage of what was a complete design, supply, install and commissioning of a Zehnder ComfoAir Q600 Mechanical Ventilation with Heat Recovery (MVHR) system – that also features cooling air-conditioning.

Although we’ve commissioned many Zehnder and PAUL MVHR units in the past, this was the first time we have designed a system with active cooling to deal with potential summer overheating here in the UK.

Here’s a snapshot of the 3D detailed ductwork design:

Complicated ducting for an MVHR system with ComfoCool

The ComfoCool unit sits right on top of the MVHR unit, so it’s very easy to integrate into an MVHR system. The supply ducts have to be wrapped in foil-backed insulation to preserve the “coolth” that the unit is providing to the supply air on hot days.

The MVHR and the cooling unit are linked by a simple communications cable:

Comms cable to link the MVHR to the cooling unit



Zehnder ComfoAir Q600 with ComfoCool attached

The cooling unit will kick in automatically when the main unit detects that the internal temperature of the home has reached 25Deg C or above. It does this by measuring the extract temperature.

The Q600 unit also has variable summer bypass, so on warm days it can vary how much heat it recovers back into the home and how much it exhausts outside. This is important on spring and autumn days when it’s very sunny (so lots of internal solar gains) but the air is still very cold.

Using an integrated unit such as a Zehnder ComfoCool is a better alternative to air conditioning. It won’t provide that immediate high volume blast of cold air that air conditioning units provide, but it will provide constant background cooling on the warmest days, which is much more comfortable than a noisy AC unit blasting out cold air.

Cooling through ventilation

We’re really pleased at Enhabit that we’ve completed our first MVHR system with integrated cooling technology. As the UK weather moves generally warmer, these cooling options are going to become more and more important in the future.

If you have a building project and you’d like to know more about how you can integrate cooling into your ventilation strategy, please feel free to contact me or write a comment below.




  1. Hello,
    I have a Zehnder comfocool system in our flat in London and I’m looking to get it cleaned. Do you offer this service or know of a company that do? Many thanks in advance.

    • Hi Charlie,

      Yes, I think we can help. I’ve emailed you from my work email address at Enhabit so we can talk more.

      Best wishes,


  2. Hi
    Is the “Zehnder ComfoAir Q600 Mechanical Ventilation with Heat Recovery (MVHR) system” recommended for the warm climates i.e hot summers (up to 36 degree Celsius) with cold winter climates (down to -10 degree Celsius)? Does the integrated cooling system with MVHR meet the cooling demands in this climate condition?

    • Hi there,

      An MVHR system is first and foremost for ventilation, so it’s suitable for all buildings across all climates that require good indoor air quality.

      The climate you describe sounds like Central or Western Europe, where thousands of MVHR systems are installed and working very well. If the house has been designed with limiting the risk of overheating in mind then the ComfoCool and MVHR system will be a welcome addition – but it’s not as powerful (or as noisy!) as air-conditioning. I’ll contact you from my work email address to discuss your project more.

      Best wishes,


  3. Hi, I’m researching for a new build house in Chichester. We are interested in the Zehnder Comfocool Q600 system with the MVHR as we are worried about overheating in the summer. Can you give me a ball park figure for this unit so we can decide if we can add it to the (tight) budget?

    • Hi Alice, the ideal way to minimise the risk of overheating is via external shading (eg, trees, canopies, brise soleils, window awnings, etc). That way the solar radiation doesn’t hit the windows in the first place. Internal blinds don’t work as well because 90% of the heat energy has already passed through the glazing. The second-best option to mitigate over-heating is passive/cross-flow ventilation, ie, opening at windows at night (although sometimes this isn’t possible due to security, noise or pollution).

      I imagine you’ve considered all this, but I wanted to highlight that the ComfoCool is often the “third-best” option in mitigating the risk of overheating.

      The Zehnder Comfocool has a roughly 1.5kW cooling unit which will lower the supply air temperature by up to 8 degrees. Due to the relatively low flow rates in each room however, this won’t cool the room as powerfully as an air-conditioning unit – the ComfoCool would cool by around 1-2 degrees depending on the room volume and amount of glazing and solar gain. But compared to an air-conditioning unit the MVHR system is more energy efficient (a lot more), it’s quieter and it’s better for the environment. The act of the MVHR changing the internal air constantly and extracting humidity will also help limit overheating.

      I will email you separately on my work email address at Enhabit with pricing for the Zehnder Q600 + ComfoCool unit – this will also include detailed ductwork design, supply and commissioning.

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