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B-Vent? Running Up Exterior Wall Of Home


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Observed what appeared to be B-vent (no legible labeling) running up the exterior wall of a home in Northern New York. This vents 4-small atmospheric venting appliances.

I know that this is not recommended due to drafting and condensation issues, and I generally see exterior run B-vent installed in an exterior wall chase.

My question - Are there metal vents other than B-vent that would allow this? What prompts my question is several other bordering homes had similar set ups.

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I don't know of any other gas vent system that would be acceptable for that installation. Maybe there's an insulated vent that's available, but someone (M.E.) would have to approve it.

What's in the pic is a B-vent. In addition to support and possible sizing issues, I would tell them that any more than 5' exposed requires an unvented enclosure or chase that has a minimum of R-8 insulation.

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Thanks for the responses.

I had never checked out HT vent before.....

"woven ceramic fiber refractory blanket - surrounded by two inner walls"

Yes this might just draft alright in this climate.

I don't think I could get my wallet to open that wide....thanks for referencing though....good to know about.

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Wouldn't an HT vent be acceptable for outdoor applications?

Just size it properly and open that wallet wide.

Marc

B-vent is "acceptable" for outdoor applications, there's just no prescriptive guideline for using it outdoors below the roofline. I'm not at all sure that A-vent (what you can HT) is any more acceptable in that location when used with a gas appliance.

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I wrote this B-vent installation up as "not recommended" as installed, and specified why. I additionally recommended that this be further evaluated when the HVAC professional is called in to further evaluate the heavy corrosion near the draft diverters of the 2-28 year old forced air furnaces and their 28 year old air filters.

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My house has a b vent flue exposed like the OP, 24' of vertical. I took the top 2' off when I did the roof a month ago. It was completely blown, acid eroded inside and rusted nearly through outside. The section below is fine.

I have IR images of it somewhere. Mid 20s ambient, mid 60s pipe temps, upper 70s at the joints.

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