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Community and Q&A

Passive / manual makeup air damper

samueldnewman | Posted in Green Products and Materials on

Hi all, I’m having a hard time finding a good damper for a passive makeup air duct. I’m installing a small wood stove in a tight (shooting for under 1.0 ach50), high R (approx R-40 walls and R-60 roof) house in CZ6A (Vermont). The wood stove will over heat the house but we want it for power outages (customer not interested in PV). I want to run a small (4″ or 6″) duct through the wall behind the wood stove to provide makeup air, and all I’m looking for is a simple damper that can be opened/closed manually from the inside of the house. Of course I’d like to be as tight as possible. If we can, let’s please skip the discussion about installing fuel burning appliances in a tight house and go straight to the suggestions of where to find a damper.

Thanks very much!

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  1. CramerSilkworth | | #1

    Most manual dampers are kinda chintzy and not really made for repeated use, usually only one-time balancing. Look for a blast gate / slide style damper, often used on woodworking/etc dust collection systems. Just make sure it's all metal, unless you're sure there's no way for ash/embers to fall into the air inlet duct.

    1. Trevor_Lambert | | #2

      Something like this:

      As is, it's not going to be all that air tight, but I imagine you could add some kind of high temp gasket.

  2. natesc | | #3

    I don't think you will need a duct for the woodstove.

    I would suggest not installing it, and only doing so if you are actually having an issue in practice.

    Crack a window to get the stove going, and after a couple minutes the stove pipe will be hot enough that you can close the window and it will easily maintain the draft, even with other vents exhausting air.

    1. Trevor_Lambert | | #5

      In a relatively airtight house, where is the makeup air coming from after you close the window?

      1. Expert Member
        MALCOLM TAYLOR | | #6

        Hopefully from the blast-gate you linked to. Very cool solution!

  3. samueldnewman | | #4

    Thanks all for the input. The blast gate is brilliant. I'm a woodworker and really should've thought of that!

  4. propeller | | #7

    We've been living with a masonry heater in a Passivhaus (0.37 ach50) with no make-up air. We have no problem and can even have the range hood fan running on low at the same time. But we must open a window if we need to run the dryer...

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