wall shield thickness...

[trailblaze]

i'm going to make a sheet metal or aluminum wall shield...

i've found some ceramic spacers on Northlineexpress.com to use to mount the shield, and the people i work for own a body shop and have a race car garage (they have a few race cars) and they can get me either sheet metal or aluminum sheets....they also have all the tools to cut it and bend it (brakes)

which is better sheet metal or aluminum.... and what gage do i need?

i think they can only get the aluminum in 14 or 16 gage? and it's already powder coated black...which is the color i wanted

 

[Diabel]

Either will work, though aluminum will ding easier over time. As for mounting you could use metal 2x4 studs, that will give you 1" space between the wall & the shield.

 

[trailblaze]

oh yeah... well the aluminum is a thinner thickness than the sheet metal i can get...

won't the metal studs transfer the heat from the shield into the wall?

 

[trailblaze]

just read up that 24 gage is the recommended thickness for sheet metal... i assume this holds true for aluminum too...

any thought on the metal studs and heat transfer problems?

 

[Diabel]

Not to the point of concern, I think. Just make sure you have air gap at the top & bottom.

 

[trailblaze]

yeah, i planned on leaving 1" at the bottom and the top is only going to be 37" off my hearth sooo the gap is ok there...

 

[Highbeam]

Is this wall shield required to meet some sort of special requirement in your installation? If not, and I doubt it is, then it doesn't matter what you use or even if you have any air gap at all since the only criteria is that the chosen materials are not combustible. Your stove should have been installed with proper clearances to combustibles already so you could use aluminum foil nailed to the wall if you want.

The aluminum has a much lower melting point than steel but would look cool if it was polished and left bare. Maybe diamond plate? The black coated metal will absorb more heat than unpainted metal. The mirror like finish might actually "reflect" the radiant heat back into the room like a mirror.

 

[trailblaze]

well the wall shield is to help keep my drywall temps from reaching 185+....which is what is was a few nights ago before i shut the stove down...i kind of like the simple look of the metal shield so i'm going that route...

my stove is "almost" with-in the clearences .... so this is more of a extra piece of mind shield.

i think i need the air gap since the walls got soo hot and this shield is going to most likely get hotter due to the heat retaining properties of metal...


i'm sort of concerned about the heat that will still be behind the metal.... in the air gap... perhaps going with a stainless metal will reflect more heat instead of absorbing it...

 

[myzamboni]

Trailblaze, I went with stainless as long term it will keep its appearance better than sheet metal (galvanized). Aluminum would work too, but it dings/bends real easy.

24 gauge is the minimum, so you can go thicker, but you will pay for the extra material.

 

[fossil]

The whole purpose of the 1" airspace, ventilated top & bottom, is to create a vertical channel where a natural convective flow will establish itself...cooler air entering along the bottom as the warmer air exits along the top...a continuous heat transfer process while the stove is generating heat. Properly constructed & installed, there will be no appreciable "heat retention" in the airspace...quite the contrary. Rick

 

[trailblaze]

myzamboni

thicker as in a smaller number gage right? like wire....

do you think i'll have any issues with hot air behind my shield? it'll be open on the bottom and top and on one side... i want to bend the one end over to not show the gap

also, how did you fasten your shield to the wall?

 

[Adios Pantalones]

Ditto on Pookball Warping Booster. Painting it black will make it absorb more heat.

 

[trailblaze]

The whole purpose of the 1" airspace, ventilated top & bottom, is to create a vertical channel where a natural convective flow will establish itself...cooler air entering along the bottom as the warmer air exits along the top...a continuous heat transfer process while the stove is generating heat. Properly constructed & installed, there will be no appreciable "heat retention" in the airspace...quite the contrary. Rick

you think the air will move that much on it's own? thats cool if it does...

like i said before.. this is just to get my wall temps from hitting 185+....i know they may still be hot... but not that hot

I'm playing it safe! i don't need my walls to spontaneously combust

 

[trailblaze]

Ditto on Pookball Warping Booster. .

haha what?

 

[trailblaze]

haha ok i see what he was saying... WOW

 

[begreen]

Considering the wall shield is out of harms way, it should be fine with 26 ga sheet metal. The first one I made was out of this gauge and was painted white to closer match the wall. Stiffer gauge metal will stand up better if there's a chance of bumping it with logs, hearth tools etc., but it will not afford greater heat protection. I like the edges of the heat shield to be hemmed (folded over) so that there are no sharp edges to cut oneself on. It's hard to do this neatly with too stiff metal. 26 and 24 ga metal hem pretty well. 22ga starts becoming a bit hard to do as nicely.

 

[fossil]

...you think the air will move that much on it's own?...

Unless your house is exempt from the laws of physics. Rick

 

[begreen]

That's seems overkill pook. Is this a guide book or mandatory code? Gotta link?

 

[fossil]

NFPA 211 says 24 gauge steel (0.024", or 0.61mm). Rick

 

[begreen]

Thanks Rick, I stand corrected. I thought it was 26 ga, but then again when I made that shield it was for our 1979 Resolute.

 

[fossil]

Well, it may not matter, (not like we're trying to reduce the clearances on an unlisted appliance), as OP says he's "almost" in compliance without the shield, but just wants it to calm his nerves. No argument from me there. I do think that a bit of study of the electromagnetic spectrum and the behavior of energy of different wavelengths will lead to the realization that reflection plays little role in the infrared, which is where we are with woodstoves. What's important is to establish that ventilated airspace using a non-combustible material, then let natural convection take care of moving the heat up & outta there. Rick

 

[Adios Pantalones]

I do think that a bit of study of the electromagnetic spectrum and the behavior of energy of different wavelengths will lead to the realization that reflection plays little role in the infrared, which is where we are with woodstoves. What's important is to establish that ventilated airspace using a non-combustible material, then let natural convection take care of moving the heat up & outta there. Rick

While I do not know which effect will be greatest- the air flow or the reflective nature of the metal, I disagree with your assessment of the EM reflection. It is a major effect, and in fact I just yesterday modified 2 spectrometers that employed polished metal mirrors for the mid-IR (We make hand-held Raman and FTIR systems).

Further- in building a kiln, a marked decrease in radiated heat is noted with just the addition of a heavy aluminum foil wrapping (use heavier material mostly for handling/to avoid ripping). I used aluminum flashing, myself. I also made stand-off shields for the wooden beams around my kiln chimney using flashing that have really paid off.

Further- look at the IR reflective properties of a "space blanket"- they are incredibly efficient for their mass because they reflect IR.

(I'm a spectroscopist, kids- try this at home at your own peril- LOL)

 

[fossil]

Reflection? Or absorption & re-radiation? Are we real, or virtual? Do I exist, or am I just another server? I, of course, defer to AP in all things spectroscopic...just don't let him approach me with an endoscope. Rick

 

[Adios Pantalones]

There is reflection. Unlike my ex wife- who has no reflection.

 

[fossil]

Mine seemed to have a problem with high resistivity. Rick