Wall protection

[nygiants0180]

I have a question about the wall protection behind a Vermont Castings Encore Non-Cat Woodstove. Do I need a 1" airspace out from the wall if I use 3/4" micore, 1/2 durarock, then tile? Can I just screw this to the wall with no airspace? I just think this way there will be more strength and rigidity. The manual does not stay anything for R-Value of wall protection.

 

[DAKSY]

NFPA 211 says you need the one inch air space...
One inch MIN at the bottom of the wall shield to let the air in.
One inch MIN behind the shield to let the air move.
One inch MIN at the top to let the air out.
OK?

 

[Mr. Kelly]

I'd like to know more about this NFPA code.

I'm also building a hearth for a Lopi stove. The owner's manual states the clearances from all combustibles. Dealer says that should do it, and that all stoves are tested by EPA standards, and that all clearances have been thoroughly assured. I was under the impression that walls would be fine with clearances observed. Am I wrong?

Why would NFPA differ from EPA standards?? How do I know I'll be safe?

 

[fossil]

Only if you have an old unlisted stove, or one for which you have no manufacturer's documentation would you default to the provisions of NFPA 211. And, since it's a standard, not necessarily a code where you live, it would behoove you in that circumstance to consult with your local Authority Having Jurisdiction before putting any $$$ time & energy into a project which might not satisfy the local requirement.

If you have the manufacturer's documentation for your appliance, and it spells out all the required minimum clearance to combustible materials in all directions, then that's what you go by. If there are words in that documentation to the effect of "these clearances may be reduced by the installation of an appropriately constructed & installed heat shield", then they can be. In that case, the guidance for bulding & installing such shielding contained in NFPA 211 is germane. If there are no such words in the appliance manufacturer's documentation, then the clearances cannot be reduced by the use of any sort of shielding, so installing such shielding would simply be for your own peace of mind or whatever, but the appliance would still have to be installed observing the minimum CTC's just as if your shielding wasn't there. Rick

 

[Slow1]

I have a question about the wall protection behind a Vermont Castings Encore Non-Cat Woodstove. Do I need a 1" airspace out from the wall if I use 3/4" micore, 1/2 durarock, then tile? Can I just screw this to the wall with no airspace? I just think this way there will be more strength and rigidity. The manual does not stay anything for R-Value of wall protection.

If that is one of the newer "downdraft" model stoves then I recommend that you exceed the minimum specs, particularly on the rear clearance/protection. I found that the wall behind my stove would run over 150*f as a norm - and sometimes considerably higher when installed to minimum required by the manual (with rear heat shield and flue collar shield). This is a wall that is painted off-white on top of drywall. Not a protected wall (specs didn't require it...). Note that this is much hotter than I can hold my hand to which is why I decided to put a number to the temp using the IR thermometer. Hotter than I considered safe in any case. Much of the combustion in the VC Encore downdraft stove happens in the back of the stove so that is the hottest part. If I were to install one I would likely put up a shield on the wall with the 1" air gap AND exceed minimum distance to the stove (whatever it is once you shield the wall). Call me paranoid but somehow I don't think that these stoves always run exactly as they did in the testing labs once installed in the real world.

 

[Mr. Kelly]

Thanks Rick.

That was my understanding.

I did put in an email to the local building inspector and told him what I was up to and asked it there were things I should consider before installing, and also the expectations in regards to permits/inspections. I presume he'd tell me if there were things out of the norm that I should be considering, which he didn't. He said he would need to come out for the post-install inspection. Hopefully, it won't be at that time that he points out things I may not have known!

Thanks again!

 

[begreen]

I have a question about the wall protection behind a Vermont Castings Encore Non-Cat Woodstove. Do I need a 1" airspace out from the wall if I use 3/4" micore, 1/2 durarock, then tile? Can I just screw this to the wall with no airspace? I just think this way there will be more strength and rigidity. The manual does not stay anything for R-Value of wall protection.

If the wall shield is to achieve reduced clearances, per mfg. testing, then it has to be built to NFPA211 standards. That means with the air space. But don't worry, no one walks on the walls, so deflection is not a big issue. 1/2 cement board is plenty rigid enough in this application. Use doubled-up 3" wide strips of the cement board attached to the studs to create the 1" air space.

If the clearance to combustibles for the stove installation are to mfg. testing spec for non-wall shield distances, then no problem with your plan. That would be a bit of overkill for peace of mind, but perfectly acceptable.

 

[fossil]

I'd like to know more about this NFPA code.

I'm also building a hearth for a Lopi stove. The owner's manual states the clearances from all combustibles. Dealer says that should do it, and that all stoves are tested by EPA standards, and that all clearances have been thoroughly assured. I was under the impression that walls would be fine with clearances observed. Am I wrong?

Why would NFPA differ from EPA standards?? How do I know I'll be safe?

Well, not only are you hijacking this thread, but you're talking about an apple and an orange. The EPA, of course, is the Environmental Protection Agency, a part of the Federal Government. Their involvement in solid fuel-burning appliances is to specify requirements for emissions to the atmosphere. Their standards have spurred the industry to develop and manufacture cleaner burning appliances. Many states now require that any new solid fuel-burning appliance installation be an EPA-approved unit.

The National Fire Protection Association (NFPA) is a professional organization just like ASME, SAE, and tons of others. They convene groups of industry experts and they compile, publish, and update/maintain recommended standards for such things as structural integrity, corrosion resistance, and (in the case of NFPA) fire safety. NFPA 211 is one tiny part of what NFPA publishes. In it, one can find (among other things) guidance on the safe installation of a solid fuel-burning appliance, including the construction and installation of heat shields for protection of combustible walls. As I said in a previous post, if the manufacturer's documentation for your appliance makes no mention of reducing the stated CTC's through the use of installed wall shielding, then you can't reduce them. Whether or not the specific provisions of NFPA 211 apply to you depends upon whether or not they've been incorporated as "Code" (law) where you live.

The EPA and NFPA are concerned with two completely different aspects of wood burning appliances...the former how clean burning they are, the latter how safely they are installed and operated.

Testing of woodstoves is typically done by an independent testing lab, quite commonly Warnock-Hersey. The results of this testing determines whether or not the appliance meets EPA emmissions criteria, and is also used to specify the minimum clearances to combustibles for the specific appliance. The testing is conducted in cooperation with the Underwriters Laboratory, who also needs to pass muster on the safety of the appliance. Rick

ETA: At least, this is my amateur understanding of it all. Someone like Mike Holton could most certainly correct my misunderstandings, smooth out my rough edges, and fill in my empty holes in trying to present a primer on the subject.