Heat Shield Advice

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tcalo
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Post by tcalo » Wed. Aug. 24, 2016 9:00 pm

I used to have a sheet of cement board acting as a heat shield hanging on the wall behind my stove. I planned to eventually run cement board to the ceiling behind the stove and cover it with stone. That project started getting quite expensive fast. I have since gutted the room and am on the home stretch of a renovation. I decided to ditch the cement board and go with an idea that I saw here some time ago. I'm thinking about making a free standing metal heat shield to stand behind the stove. It would be a semi circle sheet of metal painted black to fit just behind the stove. I have a friend that works in a metal fabrication shop so getting it made shouldn't be a problem. I just have to be sure I would be able to move it if I ever needed to. I'm stumped on the metal thickness to use and how close/far behind the stove should it be placed? The reason for air gaps on heat shields attached to walls is for the purpose of venting the hot air behind the heat shield, correct? I assume an air gap isn't needed on a free standing shield. Also, the room is built on a concrete slab. I plan on finishing the floor with ceramic tile. Since it is a concrete slab and ceramic is heat resistant I assume it would be safe for the stove to sit directly on the tile without using floor protection. The ceramic tile should be able to take the weight of the stove, right?

 
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blrman07
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Post by blrman07 » Wed. Aug. 24, 2016 9:54 pm

You should be just fine as long as the slab is on dirt with nothing combustible under it. To get the exact skinny on heat shielding go to NFPA 211. Have a cup of your favorite beverage handy because it is mind numbing boring until you get to the part you want.

 
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oliver power
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Post by oliver power » Wed. Aug. 24, 2016 10:04 pm

The heat shields I've made are about .018 thick aluminum. A series of vertical channels, sandwiched between two flat sheets of the same .018 aluminum. Legs at each corner hold it an inch off the floor. The thin material absorbs the heat. Cool air flows in from the bottom, up through the channels, carrying heated air out the top. Works very well!!!

I made one for behind my parents wood stove (Back when they had a wood stove). The wall before having the heat shield was scary hot. Once the heat shield was installed, the wall actually stayed cool.

Actually, what I used is aluminum trim coil for trimming out windows & doors when siding a house. They have it in .024 thickness, should you want to go a little heavier. Personally, I would not go any heavier than .032. Buy it in black, or any other color you may want. You can buy 4 x 8, or 4 x 10 sheets of this aluminum.

 
grumpy
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Post by grumpy » Wed. Aug. 24, 2016 10:54 pm

Photos would be good.....


 
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Richard S.
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Post by Richard S. » Thu. Aug. 25, 2016 12:30 am

tcalo wrote:The reason for air gaps on heat shields attached to walls is for the purpose of venting the hot air behind the heat shield, correct?
If you leave a gap at bottom and top it will convect and if it's going to get really hot this will keep it cool, this is also much more efficient because it will reflect heat and the heat it does absorb can't conduct into the wall as easily. It would be good place to add some ducting if you want to distribute some heat but it's going to pick up a lot of dust.

 
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tcalo
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Post by tcalo » Thu. Aug. 25, 2016 2:26 pm

I did add duct work throughout my house and it works great, but it does get a bit dusty. I cut an intake register above my stove and put a filter in it. I change it every few days. I have registers in the bedrooms on the other end of the house. It creates a loop by pushing the cold air back to the stove room. So...back to the heat shield. A free standing shield would not need an air gap since it wouldn't be attached to the wall, correct?

 
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Lightning
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Post by Lightning » Thu. Aug. 25, 2016 2:47 pm

I would say no. If the heat shield gets warm, a column of air will flow up both sides of it just from natural convection which in turn will prevent it from getting dangerously hot. Personally, I would use something highly reflective in the shape of a "V". Have the point of the "V" pointing at the back of the stove so that radiation will bounce off of it at 45 degree angle relative to the stove. The reflected infrared radiation will be more useful warming objects and walls adjacent to the stove instead of heating the wall behind it.

If you decide to use a heat shield that soaks up the radiation instead of reflecting it you'll be adding a lot more warm air to the ceiling (described above) and the stove already does enough of that, right? lol, unless you use a ceiling fan to blow it back down.

Just my two cents on the whole thing. :)

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