Broan ERV with Zehnder Comfotube
I’m considering retrofitting our house in CZ 6 with an ERV (current setup is exhaust only with passive air inlets). For various reasons (DIY, space, electrical, etc.), I’m considering a Broan ERV (160 cfm) paired with the Zehnder Comfotube system. The only space in our house that would work for the ERV/manifolds would be above the combo washer/dryer, I’d remove the shelving, see attached photo. I don’t want to duct into our unconditioned attic, so I’d have to build some chases in parts of our upstairs.
I’ve seen references in other questions to people doing this, but I’m wondering if those who’ve done this might be willing to share photos and info about your setups, especially of the ERV to manifolds setup.
And some questions off the top of my head:
-What did you use for ductwork to the exterior supply/exhaust, just regular insulated flex or rigid? Or the Zehnder Comfopipe?
-What about the exterior wall caps. What seems to be the best product, something from Zehnder or another company?
-Did you do any extra filtration of incoming air (bugs, etc.) or just rely on the ERV filter?
-Did you use the Zehnder register boxes and diffusers?
Thanks so much for any input,
Brian
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Replies
What is the appeal of using Zehnder’s piping over generic metal ductwork?
Good question. I don't have experience with the design or installation of metal ductwork. This will be a retrofit in a small house and I don't want to go into the attic (unconditioned, 20"+ of cellulose on attic floor). I think being able to run the Zehnder Comfotube(s) directly to specific spaces will be more manageable for this DIY situation.
I have a Zehnder ERV with some non-standard accessories. What you're thinking about is kind of the opposite of what I'd recommend. People often complain about the high price of Zehnder, but most of the extra cost is in the special duct and such. The unit itself is priced fairly competitively.
But if you're trying to retrofit ductwork into 2x4 walls and similarly small chases, I can see why you'd look at their comfotube. I have virtually identical tube from a different supplier. I used the comfopipe for the connections to the exterior, which I would do again. The two manifolds are third party units with a 6" inlet and 10 outlets of 3", or whatever the comfotube is, I think it's 3". I do have pictures I could upload later, I just don't have them at hand.
I just got diffusers from Home Depot. The Zehnder ones were ridiculously priced.
I used external wall grilles from Zehnder and they are fine, but expensive.
I have a coarse intake filter ahead of my ground loop pre-conditioner, and it does catch a lot of big stuff. The consensus on here is to install a large filter box on the intake. Then the filters are cheaper, and last longer. I wish I had done that. I don't think there's much benefit to doing the same on the return air side, but coarse filters on the return diffusers is a good idea. Zehnder sells those, and they can be cleaned and reused.
Do you have some manufacturer/supplier info on the pieces you used? What nearly identical pipe and manifold did you use?
What did you use for a ground loop heat exchanger? I thought Zehnder had one, but maybe not in the states anymore?
Zehnder has a ground loop unit, but the price is astronomical. I made my own.
The tubing I used came from Czech Republic, and you can't get it here anymore. Same deal for the manifold (which isn't all that similar to the Zehnder one, if I recall correctly) and most of my register boxes. At one time I did see another supplier for the tubing, but I don't remember the website. I found this one, but they're in Ireland:
https://www.heatmerchants.ie/nuaire-75mm-semi-rigid-radial-duct-50m-coil-blue-u46709
Here's a better site, still overseas but at least they have pricing. I don't know how it compares to Zehnder pricing.
https://www.bpcventilation.com/quiet-vent-75mm-x-50-metre-antibacterial-radial-pipe
Nice, I've considered doing something similar on our build with the ground loop. Seems relatively straight forward. It would be interesting to see the details on your build and control system sometime if you haven't already shared them somewhere.
Thanks for sharing on the piping.