1" clearance

[Al D. Bolt]

Does this application still require a 1" clearance from combustibles?

[Joe Funderburk, CMI]

If that's sheetrock, then it isn't "combustible" and there is no issue. Isn't sheetrock used to provide a fire barrier between the garage and home?

However, if that is a garage, then there is void in the fire barrier. The gap should be protected by a flange to prevent flame entry into the structure above the ceiling.

[Brian E. Kelly]

B Vent manufacturers will disagree and tell that a 1" clearance is required.

Can I install drywall or wall board right up against the gas vent?

No. Drywall and wallboard are considered combustible materials and should not be installed against the vent including the use of this material to close off the hole around the vent. Type B Gas Vent requires a minimum of one-inch clearance to combustibles. This one-inch is a typical clearance for all brands of Type B Vent, but each section of vent pipe is marked with the clearance required by Underwriter Laboratories, so it should be checked

http://www.americanmetalproducts.com...rivent/faq.htm

[Al D. Bolt]

I think the difference is due to the different purposes. One is with performance under the conditions during a fire (where it is considered noncombustible), and another is with performance during exposure to a constant high-heat source (where it is considered combustible).
Correct?

[Rick Maday]

Originally Posted by jfunderburk

If that's sheetrock, then it isn't "combustible" and there is no issue. Isn't sheetrock used to provide a fire barrier between the garage and home?

.

I believe it is "combustible" as it will burn.

It is "fire-resistant", not "fire-proof"

Decent article...

http://www.homeadditionplus.com/dryw...ed-Drywall.htm

[Brian E. Kelly]

Once again, it has nothing to do with drywall manufacturer, it has to due with what the Manufacturer recommends for the installation of their product. And how the product was tested by whatever agency validates the safety performance of the rpoduct(UL).

The dryall manufacturer can say whatever they want about their product............. They do no make B Vent.

Pyrolysis is also taken into consideration..................................... .....

[Bob Elliott]

Anyone know of a single problem caused in not having clearance?

[Larry D. Kage]

Originally Posted by belliott

Anyone know of a single problem caused in not having clearance?

Many fires in the north from pipes too close to combustibles. Watch the news this heating season or check with your fire department if need be for verification.

[Jeffrey Moore]

Brian,

Don't you have to have an absence of oxygen to be called pyrolysis?

No, I haven't seen or heard of a problem with a smaller that 1'' clearance but
still call it out.

[Bob Elliott]

Originally Posted by lkage

Many fires in the north from pipes too close to combustibles. Watch the news this heating season or check with your fire department if need be for verification.

Thanks, but did they blame the drywall clearance?.

[Ralph Brady]

Here is a picture of drywall in an interior utility closet that didn't 'burn' under pretty much worst case scenario with a flue! I ran into this a few years ago. I think someone made a boo boo when they were re-roofing.

[Bob Elliott]

Think I need to get a propane torch and see what happens , though I seem to recall a discussion here in the past about materials becoming more flammable over time when exposed to heat .

[Joe Funderburk, CMI]

Read all of this and pay particular attention to the last paragraph. Provided Larry's information is correct, drywall is considered non-combustible by 3 national model building codes, I don't care what the b-vent manufacturer's say about it.

http://www.nachi.org/forum/f22/b-ven...34/#post543528

[Larry D. Kage]

Remember to pay attention to whether there is wood behind the drywall within these clearance distance situations...

[Bob Elliott]

Originally Posted by jfunderburk

Read all of this and pay particular attention to the last paragraph. Provided Larry's information is correct, drywall is considered non-combustible by 3 national model building codes, I don't care what the b-vent manufacturer's say about it.

http://www.nachi.org/forum/f22/b-ven...34/#post543528

The paper is the combustible it says.