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Timberjack
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# Posted: 29 Jan 2011 07:28am
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Our wood stove will be installed in a corner and we would like to have some faux stonework behind it on the wall. Do they make a wall protector/heat shield that looks like stone/rock/brick etc.?
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Moontreeranch
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# Posted: 31 Jan 2011 10:54pm
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One added thing about real stone is the added thermal mass that those provide.
I installed a bunch of black granite behind our woodstove. The black adsorbs the low IR better.
http://kmswoodworks.wordpress.com/2010/12/01/breaking-the-dry-spell-life-at-the-cabin /
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MtnDon
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# Posted: 1 Feb 2011 01:04am
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Installing rock, brick, etc. behind and beside a wood stove does not reduce the clearance measurements. The stove should still be installed the recommended distance from the combustibles. If the rock, brick, metal... is installed with a one inch air space between it and the combustibles behind, then the clearance distance may be reduced. Stove manufacturers data should list the requirements.
I have one stove installation that uses 24 ga. sheet metal, with a one inch space. That allowed reducing the distance by about 1/3.
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CabinBuilder
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# Posted: 1 Feb 2011 10:07am
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Here is more info on woodstove heat shield and clearances.
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Just
Member
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# Posted: 1 Feb 2011 02:07pm
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I used a 4x8 sheet of cement board cut up to make 2 sides and a floor> We then painted it with high heet paint stood it out from the wall 2 in. with some scrap bits of board!! seems to work well but we don't us it a lot
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Timberjack
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# Posted: 1 Feb 2011 02:26pm
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Thanks for the link Cabinbuilder. What do you use for spacers behind the wall protector to allow for the 1" space?
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CabinBuilder
Admin
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# Posted: 1 Feb 2011 03:10pm - Edited by: CabinBuilder
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I used long screws to mount the heat shield, driving them through 1" cut pieces of pipe as spacers. But it could be anything else suitable - non-flammable.
See pic on this page.
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TomChum
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# Posted: 10 Feb 2011 01:33am - Edited by: TomChum
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Rather than putting non-combustible on the wall, I put a heatshield on the stove and it worked great. Adding a heatshield to the chimney pipe was an essential part of the success.
This was at my home, with a decorative oak panel wall getting too hot for my liking, even though it was 18 inches away. (This was with a really hot fire). The wood was so hot, hot hot to the touch - and I have thick skin. Not sure how to describe this temperature thing, but by anyone's standard it was just too damn hot!
I added a sheetmetal heatshield on the stove and it helped a lot. But the stovepipe was still cooking the wall, so I added one to the stovepipe and it solved the problem entirely, in fact it even reduced the temp of the wall below it, behind the main stove's heatshield. I don't know what 'the code' says about this kind of solution, but it solved my problem 100%. The wall gets just a little warm now. It's been 6 years and the clear varathane on the oak panelling is still 100% perfect.
Here's a photo of these 2 heatshields. They were easy to make, especially the stovepipe shield. I used a thin .040" abrasive wheel on an angle grinder to cut a shiny 4" decorative stovepipe lengthwise. The 4" size stovepipe, (open) was about 4" RADIUS, which was just the right radius for 3/4" clearance to the 6" chimney pipe. I used 3/4" long small pipes for standoffs, just two of them, one at top and one at bottom.
The oak panelling was kind of expensive and looked nice, I did not want to cover it up. The heatshields on the stove back and chimney backside are almost invisible, yet they do the job.
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TomChum
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# Posted: 13 Feb 2011 11:30pm
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....more info
Chimney pipe heatshield is about 5 feet long, starting as in the picture and going up to about ~7 feet. The chimney pipe was not so hot above ~7 feet, it didn't seem necessary to shield it any farther up.
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Timberjack
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# Posted: 14 Feb 2011 08:11am
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Thanks Tom!
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TomChum
Member
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# Posted: 14 Feb 2011 01:14pm - Edited by: TomChum
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Glad to help. Here's more information, similar project, in my shop.
The reason that heatshields are not addressed in "the code" is because any or all of these protections can be removed, at any time. For example you use it for 30 years then you get old, and your kids decide to remove all that ugly old grampa stuff. Or the painter removes it temporarily, and does not re-install. Or new owner installs a new stove, without the protections. Initial separation from the combustibles is the safest protection, and the only protection that will likely remain over time.
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OK onward into dangerous territory, I suspect some folks will be able to make use of this info. Be sure to take into account what "someone else might do...." it could be tragic.
I had only 10" between stove and the wall, so I did a lot of testing, adding stuff, burning hot test fires. By step 4 the wall is just detectably warm to the touch.
1) I knew there would be more required. First step was to add drywall to the wood wall. It got very very hot, of course.
2) Second step was to cover the drywall with 1/4" cement board. It got very very hot, and even cracked.
3) Third was to add a steel sheet with an air gap to the wall. Success. Wall temp (cement board) behind the steel sheet was almost no different than surroundings.
4) Next step was to add a heatshield around the chimney pipe. This resulted in wall temperatures just slightly above ambient.
At this point I was done, all protected for the hottest fire. (sort of, as long as all the protections were in-place)
5) Then plumbed in a bathroom ceiling can, to blow some chimney heat around the shop, this worked just great!
(the copper tube is a waste-oil burner, it worked OK, was a lot of trouble)
Stove 10 inches from the wall (!)
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MtnDon
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# Posted: 14 Feb 2011 03:53pm
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Drywall: Common drywall is faced with paper. It does not qualify as a non combustible surface, does not qualify as a heat shield.
Cement board: it won't support combustion but it will transfer heat through to the underlaying surface. You could have air spaced it out from the wall one inch and that would serve as a heat shield as well.
Metal: air spaced out it is ideal as a heat shield.
The wood studs behind the wall can be affected by long term exposure to high temperatures. The characteristics of the wood can actually change to the point where the wood may ignite when exposed to temperatures that normally are well below the ignition temperature of normal wood.
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Timberjack
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# Posted: 15 Feb 2011 07:29am
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Thanks Tom, it looks like a pipe shield is in my future. My stove is in a corner and the pipe will rise about 15-20 feet before it reaches the ceiling. I'm thinking of using some old tin I have for a wall shield with a 1" space directly behind the stove (although the stove has a heat shield built on it). Then I'll add a pipe shield for the first 8' feet or so of single walled pipe until I transition to double wall class A pipe, then on to the triple chimney pipe and out through the roof. Sound like a safe plan?
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TomChum
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# Posted: 15 Feb 2011 12:31pm - Edited by: TomChum
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I think your plan sounds good. The heat from the singlewall chimney comes into the room, then higher up, you get the safety of the double+triple which keeps the inner chimney hot inside for good draft. The redundant wall shield is good, in case the stove is ever exchanged for one with no shield.
It does concern me that I don't see pipe shields used anywhere else, or sold commercially. In my house, the shield is 1" narrower than the 6" pipe, is almost invisible, and it works, the wall does not get hot. In my shop I wrapped the shield halfway around the chimney because I was planning to add a fan duct (which works great!) but it's not attractive.
What you KNOW, with a really hot fire unprotected, will provide SIGNIFICANT peace of mind when you need to build a hot fire ----> after protected. Or someone else burning your stove in your cabin leaves the stove door open, or other dangerous modes. It has to be safe for every person using the cabin, who might ever use the stove.
I think you'll benefit by doing some testing while it's "open". Build a really HOT test fire with it unprotected - but watch it like a hawk! You might consider doing it at night so you can see it all cherry red, and also consider having a helper. You want to KNOW what happens when you have a really hot fire for several hours. You can feel the wall with your hands, and hang sheetmetal on a nail as necessary. That way you'll know how far up the chimney you need to go. I ran a hose into the house ready to spray water into the fireplace and on the wall, but didn't have to, feeling the wall with my hand I knew everything was OK (but it was HOT).
After a few hours unprotected you can hang test shields, until you know their contribution. Think of the stove+pipe as a light emanating in all directions, and imagine the shadow that the shield would cast on the wall.
In my cabin I don't use any heat shields because I have 32" clearance. But the cabin wall gets quite a bit hotter than the shielded walls at my home and shop. I hoped to add a shield at my cabin that will store the heat (maybe rock), but haven't worked on that yet.
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Timberjack
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# Posted: 17 Feb 2011 07:28am
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Got started on this yesterday and hope to finish the wall coverings today.
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