Why would you (is it required?) need 1" of clearance between a type B vent and type X drywall if the drywall is fire resistant? I always write it up, but I am beginning to wonder why.
I believe some of it is to stop transfer of heat to nails or screws
Thanks Larry, I always search the forum first before asking a question, but I searched the HVAC forum and only went back a little less than 3 years. It looks like the issue is open to some interpetation, although it was definatly leaning towards being OK.
Also the paper is not fire proof unless it is treated , Stay with the 1 inch clearance to be safe .
Page 2, first paragraph by manufacturer states “Drywall is not combustible or explosive.”
But NFPA classifies it as limited-combustible.
[FONT=Times New Roman]***[FONT=Verdana]In regard to gypsum wallboard***[/FONT][FONT=Verdana], the product’s paper facing prevents it from passing ASTM E 136. However, because it does have a demonstrated ability to perform in fire rated assemblies, the NFPA has placed it in a special classification called limited-combustible. This category distinguishes gypsum wallboard from other, more highly combustible products. To qualify as limited-combustible, a material must have a noncombustible structural base or core, a surface less than 1/8 in. (0.3 cm) thickness and a flame-spread rating of 50 or less.
[FONT=Times New Roman][/FONT]
[FONT=Times New Roman][FONT=Verdana]On top of those two definitions, one should consider whether there is framing wood within the “clearance to combustibles” distance even if there is drywall between it and the vent pipe.[/FONT][/FONT]
[FONT=Times New Roman][FONT=Verdana][/FONT][/FONT]
[FONT=Times New Roman][FONT=Verdana]
Good post Larry.
B- Vent manufacturers say NO, and I believe underwriters Lab has not signed off or tested B-Vent to a less than 1" clearance.
Manufacturers requirements always override “codes” (except in cases where codes are prohibitive).
Generally, vent manufacturers require a minimum clearance (depending on the type of vent) to combustible materials **AND **building materials, which means, if it’s not part of the vent system, it must not make contact with any other building materials unless it has a “zero clearance” listing.
Time, the Enemy
Because your heating system “has worked just fine” for years is of little comfort. Time is working against you! Pyrolysis accomplishes its destruction in a matter of years or months. In a test conducted by the NFPA, a stack of wood fiberboard's (1/8-inch thickness) was exposed to a heat source of only 228°F. The wood self-ignited in only 96 hours! Ordinarily, a piece of 2" x 4" construction lumber has an ignition temperature of approximately 500°F. Exposed to moderate heat for a prolonged period, however, this ignition temperature is reduced and the wood is capable of self-igniting spontaneously. Like the NFPA 211 standard, both local and regional building codes designate minimum installation requirements. To use less than the minimum is to** invite disaster.**
I have noted of scholarly members much like yourself, Roy Cooke and Marcel Cyr and Mr. J. Pope being three more, a unique quality of posting relevant historical material form NACHI message board posted any time in the past.
Like abracadabra presto magic …Pooof!!! 2006 dates this one.
DO YOU TIME TRAVEL?
IS THERE A BLACK HOLE YOU HAVE MAGICALLY TAMED ALLOWING YOU TO GO BACK IN TIME.:shock:
Are the archives a clue to them magical quest?
Larry…is there some ritual, a native right of passage pre say Nick Gromicko sends you on…like the Maasai Warriors in Kenya sending a young boy reaching maturity into the forest with only a bow and nothing else for days eat off of nature and kill wild beasties to make them into a man?
Thats why kenton was in Africa, its all making sense now!!
Larry… tell me if I am getting warmer…Maybe an incantation or a series of secretive narrates before you enter your computer…no no no a you wave a magic wand over their computer screen, sorry I was stretching with the incantations…ha ha ha , how foolish of me. Sorry.
Either / or… I am satisfied just to be able to see the magic appear when I am lucky enough to be here on the grand INACHI MB.
Psst, Larry, can you tell me
Thanks for the kind words, Robert, but all I do is use the “search” function at the top of this page or I do have some saved reference materials on my computer.
A member for 4 years and still unaware of all the magic INACHI has to offer every member.
I consider NACHI the black hole of the home inspection industry universe swerling like a vortex. By doing so it is creating its own gravitational force swallowing information at speed of light to feed its members inside.
One thing I do know as fact Larry is that, ***you and many astute members***are true free thinking home inspection warriors.
Once sent into a home with nothing more than the bare essentials, will surely survive and exit the same way you entered, a true warrior working on behalf of your client and the INACHI tribe.
Just a bit of creative license.
OK now I am worried, exploding drywall?