19th century solution to a new problem

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Y’all might be tired of hearing about it but I’m gonna’ post it anyway… ‘cause it’s the Internet and I can if I want, Al Gore says so.

When I was planning my furnace build from the Pacific Energy stove, one concern I had was the amount of radiated heat lost through the “glass” door (maybe not technically “lost” ‘cause it radiates into the basement, but that’s not where I want it). I was correct, a ton of heat radiates through that door… heat better put to use warming the area on the floor above. My first thought was to build the plenum completely around the stove with a door in it, to access the firebox door… but decided the chances of introducing smoke and ash into the forced air system would be too great. I decided I’d have to live with the “leakage” of heat, or replace the “glass” (I guess it’s actually clear ceramic, invisible to inferred, or radiated heat) with steel plate.

We’ve had some cool mornings this week, and because I’ve replaced the storm window with screens, I’ve had a chance to play with the new build a few times. This morning (67[sup]o[/sup] in the house), as I was getting the fire going and feeling that heat on my legs… it dawned on me if I could simply reflect that heat back into the firebox it would be used to heat the firebrick and steel, greatly increasing the efficiency of heating the floor above. I’m forcing air around the firebox, pulling heat away at a greater rate, so reflecting heat back in shouldn’t cause any sort of problem as long as the fire is properly regulated.

Using my semi-professional knowledge of metal properties… Aluminum has a unique characteristic, it reflects near 100% radiated (inferred) heat. The aluminum itself will get hot from heat energy, and will transfer that heat to another solid substance if it’s touching it, but won’t radiate heat into an air space. I hung a piece of aluminum foil in front of the door, and now I can place my hand within an inch of it and feel no heat. I have the draft control set as low as possible and she’s a pumpin’ heat into the upstairs… I may even haf’ta close the flue damper some. My plan is to take some aluminum plate and make something that will hook on the door, with a handle so it can easily be removed, and sit about an inch or so away from the glass…

And before y’all start tellin’ me… Aluminum melts a 1220[sup]o[/sup] (most alloys require at least 1100[sup]o[/sup]), boils at over 4000[sup]o[/sup], and requires the temperature of the sun to burn. It does not create any gasses (poisonous or otherwise) when hot, but can react with other substances to to create gasses. The only problem with aluminum is that it can fail catastrophically if subjected to repeated heating and cooling, so it can't be used as a structural component of a stove or furnace... but would be perfectly safe as a reflector.

addendum: Oh, and by the way, if you try this experiment with aluminum foil, do not let any of it touch the ceramic glass. Somehow I let a small area lay against it, or the heat somehow pulled it against it, and it's gonna' be a real PITA to remove... if I even can remove it.
 
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Good idea! Now if you want extra heat downstairs just remove the plate.
I also used aluminum on one of my shop furnaces pipe. I took aluminum flashing and bent it into a u shape and put it on the back side of the stove pipe all the way to the ceiling.
The wood furnace was tucked into a corner and the pipe was close enough to the drywall to make it pretty warm. Once the flashing was installed you could hold your hand behind it and feel nothing. Plus it radiated the heat forward into the work area. I wired it on in a way that the aluminum was about 2 inches behind the pipe. Virtually free standing.
 
There's a furnace from Napoleon that had a glass door with the option of ceramic so it's insulated. Our door is glass on our furnace and I have thought what if it was insulated? In the end I enjoy having the glass. We have no heat registers in our basement which is 1200 sq ft and highly leaky. No heat comes through our air jacket because it's insulated, so I'll take the heat from the glass. We get enough heat to warm the basement plus enough heat to keep the 2400 sq ft above warm from the ducting so I don't worry about it. I figure that glass not only allows for a view of the fire, but more btus put into the house. We have a large secondary heat exchanger, so our flue temps are lower than most units. So do you see an increase in heat output with the foil?
 
laynes69,
Yes, I do believe I'm getting, "an increase in heat output" (as in warmer air), the air coming from the duct does feel pretty warm. What I can say for sure is the draft is set at the absolute lowest setting and and I'm still getting really warm air... Which means I should get heat output for a longer time from any given fuel load (longer burn time).
 
Amazing how something so simple can have a dramtic effect....wonder if putting an aluminum shroud over Washinton DC would make the rest of the country more effecient?

Seriously tho...your little invention just might save you some grief on those cold mornings when you forgot to reload after a night of cold beers!
 
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