# 6" Air Duct Collar for wall pass through



## carmon (May 8, 2010)

not sure it helps you...still need to seal it...... just seal the pipe ....


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## TarheelTerp (Jan 6, 2009)

bee-man said:


> I am installing an over the range microwave oven and need to run
> (an exhaust duct of some sort) ... above the kitchen cabinets.


 ...and then through the attic space and in turn OUT of the house through the roof.

There are several duct shapes to choose from.
And they'll all need a starting collar like in your link.

If the duct is actually going to be IN the wall I suggest that a rectangular shape (approx 3.25" x __") will be easier to fit behind the sheetrock.

Once above the ceiling and into the attic... other changes can still be made until you finally adapt to the roof vent cap:


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## bee-man (Jul 11, 2008)

carmon said:


> not sure it helps you...still need to seal it...... just seal the pipe ....


Hi,
I will absolutely seal the duct junction. However, I need to maintain a good seal between the attic and living space since the positive pressure from the WHF will push attic air through any leak. Right now, plan B is to use a foam sealant around the duct (not to seal the duct junction) but it is more messy and possibly prone to leaking after time. In my eyes, using the collar with flange on the wall will allow a good seal between living/attic space, and provide a solid mounting point for my ductwork. However, I am not sure about the negative impacts.

TarheelTerp:
The path of my ductwork is not ideal. After going through a single sheetrock panel (via 90 degree elbow), it will make a 12 ft horizontal straight run through the attic to a Broan 641 wall cap. This is still under the minimum effective length specified by the manufacture. I am slightly concerned about grease build up, though, but I'm willing to try this before resorting to other measures. The OTR microwave fan is rated at 400cfm, but that is probably rosy. Thanks for the info on roof caps.


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## beenthere (Oct 11, 2008)

12 foot through an attic? Better insulate that pipe.


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## bee-man (Jul 11, 2008)

This is just a closing post of my solution.


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