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ERV ductwork

Russgs | Posted in General Questions on

I am planning to build a 2000 ft^2 walkout bungalow (zone 7a) and will be ducting the ERV distribution independently. In-floor hydronic heating in the basement and forced air with hydronic on the main floor.
I am looking at alternatives to Zehnder (mostly due to price). My question isn’t really about which ERV to select, but how people have been ducting other manufacturers products. I do like the fact that the Zehnder has all the right accessories to run inside 4 inch stud walls and the diffusers look good and are paintable and adjustable.
The basement will be easy as everything is run in the ceiling joist space. But for the main floor, is there any other products on the market comparable that can run inside the 4″ stud spaces, can be well sealed, wall diffusers that look good and are adjustable? I do have an opportunity to build some interior walls with 6 inch studs, but not all.
Thanks in advance.

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  1. Trevor_Lambert | | #1

    There are competing brands to Zehnder, but they are harder to find, and not likely to be a lot cheaper. You might look at spiral wound metal duct. It's not super cheap, but probably cheaper than the Zehnder type stuff. Pro is that it's much bigger in internal area, con is that it would be more finicky to install and take much longer.

  2. norm_farwell | | #2

    Zehnder sells component parts separately, so you could graft zehnder duct and grills onto a cheaper erv unit. But then you won't get the benefit of zehnder's design+commissioning expertise, which can be worth quite a lot.

    1. Trevor_Lambert | | #5

      The Zehnder accessories and duct are actually what makes it expensive. If you compare the units to similar performing competition, it's not all that different.

  3. MattJF | | #3

    6” or 8” oval duct will fit in a standard wall cavity. It works well for the low flow rates of an ERV. You probably would run these off a trunk and branch style layout instead of home runs.

  4. Expert Member
    Akos | | #4

    I would figure out the flow rates you need. With a simple enough layout, most of the runs can be either 3" or 4" round duct, with the occasional 5" round (or 6" oval) pickup.

    I like working with semi rigid aluminum ducting (similar to dryer vent pipe but longer). These are slightly more restrictive than hard pipe but easier to work to snake through walls. HVAC supply places can get you these in long lengths, so you can do complete branch runs without any fittings.

    1. Russgs | | #7

      What did you use for wall diffusers and are they adjustable so you can balance the system?

      1. Expert Member
        Akos | | #8

        Standard 3x10 registers, you can also use standard round diffusers. Balancing is best done with dampers at the trunk, this way the balance can't be thrown off by somebody adjusting the registers.

  5. Russgs | | #6

    Thanks to all for the replies. Looks like I have options.

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