B Vent Window Clearance

**Jim Robinson** · 06-15-2007, 12:22 PM

This B vent for furnace and water heater is about 5 feet from the operable window. I noted the clearance less than 8 feet to the sidewall, but I thought there was something else about being so close to an operable window. Anyone else know of this?

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Brian E Kelly · 06-15-2007, 12:33 PM

That vent pipe should be above the side roof line by a min. of 3 ft. unless the peak of the higher roof is less than 10' away and then it should be 3' above that.

**Jim Robinson** · 06-15-2007, 01:21 PM

2 feet and 8 feet for gas. I got that part. I was wondering about the window, although I guess you can't have a window without a sidewall, so the question may be irrelevant for this application. 3 / 10 is for wood burning flues.

Brian E Kelly · 06-15-2007, 03:35 PM

The 3/10 rule also goes for gas in my neck of the woods.

**Bob Harper** · 06-15-2007, 04:01 PM

Do you have a better pic of just the termination? It appears someone cut a hole in the lid and ran a pipe inside a pipe. I see two distinct terminations. Maybe they're mating?

**Jim Robinson** · 06-15-2007, 04:09 PM

That's the only picture I had. It was a pretty straightforward vent. There are some type of vents along the side of the pipe near the top on the outside, but they weren't connected to the flue pipe at all.

**Jerry Peck** · 06-15-2007, 05:08 PM

Bob,

Looks like they (whoever "they" are) used one of those flat top four sided vents, cut the top out, then ran the vent up through it and installed a Type Gas Vent Cap on top.

Probably because a previous inspector said 'That four sided vent cap is wrong, so Mr. Handy Dandy homeowner "fixed it".

Of course, though, that would lead me to suspect that the vent inside is not a Type B vent, but the old single wall vent which was likely in it originally.

Don't forget that plumbing vent too. 10 feet from the operable window or other building opening or 2 feet above it. If the gas vent is 5 feet from the window, so is the plumbing vent.

**Bob Harper** · 06-16-2007, 07:09 AM

Exactly my point Jerry. Don't get caught up in the humdrum such as clearances and miss the larger issue. This was tampered with or modified. Remember my warnings about red flags? Where you see one goofy thing, you're bound to find more? (yes, you can write "goofy" in your reports--They will know you're a down to earth kinda guy!) Seriously, take the holistic approach.

Just to tease you some more: does this vent require roof bracing? How do you brace vents on flat roofs? How do you penetrate the roof deck on a flat roof? That'll keep you busy for awhile! Gotta scoot. I hear a roof calling me.

**Rick Hurst** · 06-16-2007, 07:15 AM

You think this one is a bit close.

**DavidR** · 06-16-2007, 08:11 AM

Hope that termination isn't on the windward side of the house.

Regardless of clearances that could make for a bad situation.

Bob Waysack · 01-29-2010, 06:15 AM

In southern California I run into gas water heater vents closer to 8 feet to the walls at the roof. It's all stucco out here, so why is it a problem?
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Bob Waysack · 01-29-2010, 06:17 AM

In soutern California I run into gas water heater vents closer than 8 feet to the walls at the roof. It's all stucco out here, so why is it a problem?
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**Jerry Peck** · 01-29-2010, 08:08 PM

Originally Posted by Bob Waysack

In southern California I run into gas water heater vents closer to 8 feet to the walls at the roof. It's all stucco out here, so why is it a problem?

Because it is not going to vent properly there.

It is not about clearance to combustible material (although there is likely combustible wood framing in that wall) but about free air movement.