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Zehnder ComfoSystem - Frequently Asked Questions:

Q: How important is efficiency really? A few percentage points can't be a huge deal.

A: It actually can make a huge difference. It can be the difference between you running the HRV, being happy with it and you shutting it off permanently because it is too uncomfortable. In a passive house we design for the fresh air supply to be at least 17 degrees Celsius inside. Any colder, and you'll start feeling a draft, or cooling down your house too fast (read: losing too much energy). Don't be left with the wrong HRV, only to upgrade to a Zehnder unit late (which we will also gladly do for you).

Read Malcolm Isaacs story about his Earth Tube, which as a side story also depicts the switch from a "med efficency unit" to a Zehnder

Q: New Buildings? Renovations? What can Zehnder HRV's be used for?

A: New buildings are obviously perfect in new construction. The ease of installation can shave off cost and common HVAC installation time.

But even for renovations, Zehnder can be used. The building would have to reach certain air tightness or else it's effectiveness would simply be compromised. If one does open the walls though, and has access to stud cavities, you might as well install Zehnder ducting as well.

Q: How does installation compare to a regular forced air system?

A: ComfoSystems can be installed much easier and 50% faster than a conventional forced air system. The experience of many systems has shown that 50% is a pretty accurate number.

See for yourself as Berry Stephens from Zehnder America shows you how he installs a system:

Q: How do I design the geothermal ground loop required for the ComfoFond-L?

A: The Zehnder ComfoFond-L lets you preheat the supply air coming from the outside using geothermal heat. If you would like to use this option, you can find out more about the entire system, including the requirements for the loop and how to design it in this PDF (0.8MB). For a list of what you need and the details about the loop, check page 9 and 10 of the PDF.

Q: What is commissioning and what is involved?

A: Commissioning is a critical element in the installation of HRVs and ERVs. It is a systematic, documented process that is completed to ensure specific building systems perform in accordance with a building’s operational needs.

The air that flows to each register or diffuser is measured, and the total supply air and total return air flows are determined.

The total supply air and total return air flows should be balanced to provide optimum efficiency and to confirm that the supply and exhaust flows meet design and code requirements.