Take a look at the picture. I found these 2 in the attic. The buyer was present and he went to the basement where the furnace and the water heater are located. Behind the units out of view there were hi/low vents. They run inside a chase. Any reason they cannot terminate in a well vented attic. I have always seen them terminate to the exterior of the home.

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Ray, I see it done that way very often. No problem.
Is that the B vent next to your foot?

Under my foot is air exchange for the room below me. To the right is the furnace and water heater shared flue pipe.

If I remember correctly, the top of both must be >=12" above the insulation.

Raymond, please tell me you wrote up this B-vent.

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Bob,

Does that B vent look like its coming apart? It seems to get all weird shaped as it come up out of the ceiling after that 45 elbow.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Jerry, that looks like an illusion created by the insulation on top of the flue pipe.

Nick,

That's what I thought ... at first, then I realized that bottom of the 45 elbow was at the level of the insulation (you can see the top of it) and that the B vent is going up at 45 degrees.

That means the B vent above the elbow is fully above the insulation ... unless I am looking at it wrong.

(That's one thing which bugs me with this new forum, there is no way to click on the photo thumbnails when in reply mode, I will have to go back and look at the photo again, then edit this post if needed.)

The insulation is all the way down at the bottom of the 45 elbow, then there is the strap which is above the insulation, then there is straight B vent, then it gets weird shaped at about the level with the lateral brace Raymond is standing on.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

I don't know Jerry. I think it's just insulation. The truss to the right of the flue pipe seems to almost act as a form and is holding the insulation in place.

Who knows what you'll see if you pull back that insulation but I don't see any kinks or dents on the pipe suface. A different picture angle or two might make things more clear.

I guess this makes the point to check each shot and take tons. Digital film is cheap. Going back to re-inspect is not.

I blew up the photo and it appears to be some duct insulation below. However, all that insulation in direct contact with the vent is a fire hazard and the vent is improperly supported.

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What you see that looks like a damaged area of vent is bath fan flex vent behind (not in contact with) the B-vent. The vent pipe is in perfect condition, the strange angle plays with the eyes. It was strapped again just out of frame and again about a foot from the roof penetration. I did recommend that the insulation be removed from contact with the vent.
WOW you guys can pick one apart... I just wanted to make sure that the hi / lows were ok in the attic...
Thanks for all of the feedback!

I think what Bob meant by "and the vent is improperly supported" is that the vent needs to be supported in at least three axis: side-to-side, front-to-back, and up-and-down.

That one strap which is visible will allow the vent to swing side-to-side and maybe even front-to-back.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Code may say those pipes installed like that are combustion air ducts and alright but in reality they function as exhaust ducts for the space they are connected to.

Doesn't it seem odd that three pipes are run up vertical in that chase one is named a flue & the other two are combustion air pipes?

Air doesn't know to make this distinction in many cases.

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Measured Performance more than just a buzzword

That one strap which is visible will allow the vent to swing side-to-side and maybe even front-to-back.
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Good point.

The one just out of frame is a collar / standoff that is mounted directly to the framing... She does not budge.

NOW WAIT JUST A FRIGGIN' MINUTE!

I thought "combustion air" KNEW it was "combustion air" and that those pipes are one way only.

Not only the energy and air quality aspect, but what about protecting the roof framing from fire with at least gypsum board.

I know, I know, code does not require it, BUT, one must always remember 'code is minimum', nothing better, the 'crappiest way one is legally allowed to do something'.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )

Couldn't have said that any better Jerry.

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Measured Performance more than just a buzzword

I think those ducts are listed for use with Smart Air, which knows which way to go. Smart Air, when burned, becomes Smart Smoke, which knows to vent up and out instead of backdrafting.

just another reason to test so you know either things work or don't work.

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Peoples Energy in Chicago has no problem with combustion air ducts in the attic., but only if the attic is properly vented. As reasonable view.

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Eric Barker
Moraine Woods Consulting, Inc.
Barrington, IL

Has to make you ask the question "If the attic is vented how can it supply air to another part of a home?"

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Measured Performance more than just a buzzword

If the attic is venting, then path of least resistance means these ducts may feed the attic and depressurize the CAZ even worse.

Gee, should you tell David about the attic fans and turbines?

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So when one finds a system where all the combustion air is coming from the living spaces, what is the best method to obtain combustion air? I'm asking about routing and materials.

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