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I need to install an exterior makeup air duct to provide makeup air for my new stove hood.

My house is fairly tight, and I've been making energy efficient improvements including tightening the envelope to prevent air leakage. However, I do not see a single electric damper that actually seals in the closed position. They all have sizable holes in the gasket around the pivot pin.

Is there a reason this cannot exist, or have I just not found it yet? If they don't exist, is there a better alternative than a mechanical damper?

FWIW I would prefer a rectangular damper, but I could use a round damper instead -- the duct isn't installed yet.

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    The only ones I've seen like this are use in commercial/academic chemistry labs. I remember when we had one die in one teaching lab at school, and it was thousands of dollars to replace. As a general rule, the more precise, and the more robust the features, the more expensive. There probably isn't a consumer market for the product you're looking for that any manufacturer is willing to get involved in. – BrownRedHawk Nov 17 '16 at 15:41
  • Maybe, but modern houses are sometimes built to standards like 0.2 air changes per hour at 50 Pa pressure. Under those conditions, a damper like I'm describing is basically a giant gaping hole. – David Pfeffer Nov 17 '16 at 15:47
  • I don't disagree that it breaks that standard. I currently work for a multi million dollar retail hardware chain, and I can say that I' not aware of anything readily available for a consumer market. What you're looking for likely needs to be custom made, and operate more like a plumbing ball valve or similar. Time to put on your inventor hat! – BrownRedHawk Nov 17 '16 at 15:49
  • Does a UL listed smoke damper not provide a tight enough air seal? – ThreePhaseEel Nov 18 '16 at 0:36
  • It looks like Arzel may make something, they just aren't sold direct to consumer. – David Pfeffer Nov 18 '16 at 18:07
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Truly air-sealed electrically-actuated duct dampers exist. What you are asking for is also known as a electrically actuated butterfly valve for air.

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They can be found at industrial supply stores such as Mcmaster Carr, and a makeup air duct sized one will cost around $600-$2000

If you are in a DIY mood you can probably get one of the cheaper manual ones around $200 and retrofit your existing duct damper motor to it

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Yes, they sell round dampers with weatherstripping foam on either side of the louver to seal the gap you're talking about. You could also add your own weatherstripping foam to an existing damper.

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    Foam works but you have to be careful to not make it two tight or the accuator will fail. – Ed Beal Jan 10 '18 at 19:59

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