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hausdok

B Vent Too Close to Exterior Wall

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Curious what the brethren think.

Had a 7 year old home in a small subdivision (About 60 homes) today where a lower roof covered part of a garage. The HVAC guy took the B-vent that carries exhaust from the furnace and water heater up through the ceiling and attic of the garage and then out through the garage roof about 5-1/2 ft. from a side wall and 3-1/2 ft. from a un-operable window of the second floor. The vent terminates about 2 ft above the plane of the roof and about four feet below the eaves of the upper roof. (See the photo below).

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From my point of view, someone screwed up. According to my references, at the time this home was built this violated IRC 2426.6.5 and UMC 806.4 because that B-vent needed to terminate at least two feet above any portion of a building within a horizontal distance of 8 ft. I just looked it up in the newer IRC and it's under 2427.7.3 in the new code and it still says it must be at least 8ft. away from a vertical wall.

Before I left the development, I did a quick ride around to look at other houses with similar designs and noted about two dozen houses where the vents pass up through the house and attic and terminate above the upper roof, while there are about a dozen that terminate like this one. Pointed this out to the buyer.

On the way home, I got a call from the client. Seems his agent mentioned this to the listing agent who talked to the owner who told him that this had been addressed at time of construction and it had been allowed based on the fact that the window was non-operable. I guess it's the AHJ's prerogative to allow this, as long as it doesn't violate the vent manufacturer's listing and labeling; except now under the right conditions the exhaust gases from this vent will probably be pulled into the attic via the frieze vents underneath these overhanging eaves. That's a lot of steam - acidic steam - to allow into an attic where it has to flow up the underside of an OSB roof deck. It's been 7 years and the underside of the deck is still nice and clean. Still....?

I've been poking around in my references. I've looked at various codes that have been published over the life of this home and I just don't see any such exception.

Thoughts?

ONE TEAM - ONE FIGHT!!!

Mike

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It's wrong.

It's functioning. Apparently not causing adverse conditions.

IRC says a local jurisdiction can only alter codes to make them more stringent to fit local conditions, not make them less stringent.

Still, it's all uphill fighting city hall...

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The owner's word doesn't carry much weight when I'm the HI. Even if he had the AHJ's variance on paper, I'd still not totally disregard my own experience, because the experience of the average AHJ on existing housing comes up short compared to almost any seasoned HI...unless he's Chad.

Maybe the concerns haven't manifested themselves after 7 years but appliances can be changed out and new owners might have different demands of them, engaging variables not currently in play.

Marc

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I'd be more concerned with improper draft due to how the winds flow in that area. I can see strange eddy currents happening / back-drafting.

That would be my concern as well, as well as the soffit vent entry.

I would point the risk out to the buyer, tell them my recommendation stands regardless of it being allowed by the AHJ, and let them decide what they do about it.

You can lead a horse to water...

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I would point the risk out to the buyer, tell them my recommendation stands regardless of it being allowed by the AHJ, and let them decide what they do about it.

Yeah, that had already been done. I was just wondering if anyone else had any input re. this issue that might alter my opinion. Apparently not.

Thanks for the input folks. I've put this one to rest. On to the next.

ONE TEAM - ONE FIGHT!!!

Mike

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Your call is of course correct. However, the only type of person likely to call you on it, if you by chance missed it, would be an expert witness doing everything he could to try to frame you as "negligent and incompetent".

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