I want to insulate with rigid foam board the concrete wall behind my boiler

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Old 10-01-14, 06:01 PM
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I want to insulate with rigid foam board the concrete wall behind my boiler

Hello everyone. I notice outside my house on the boiler side wall that around the foundation, poured concrete, I have about a six foot wide by two foot deep area of no snow during the winter. Obviously, heat from the boiler is warming up the concrete wall behind it. I want to insulate it but my flue pipe is just two inches from the wall. So while I know what I want to accomplish (insulate the wall with rigid foam board to keep more heat in the basement and not let it go outside), I know foam board will burn (two inch clearance is not enough clearance. I was thinking about a half inch foam board with ceramic roll insulation attached to it for starters. I really don't know what I can affix to the poured cement foundation wall that will insulate at all and be fireproof. The basement is finished/insulated/sheetrocked but the heater room is not. Hence, heat from the oil burner is heating up the wall behind the boiler and it must be significant because as I said the snow always is melted behind that wall. The outside wall itself is exposed to air about 3 feet. The rest is below grade.

So any suggestions on a fireproof or resistant insulating board give the two inches between flue pipe and heater? I plan on doing the rest of the heater room walls. I should note the boiler is offset inside a 4 foot x six foot enclave. Above on the first floor is the woodstove and the buildout as seen outside is the chimney chase (it contains the lined woodstove chimney and the boiler flue. In the heater room, the flue from the back of the boiler goes up and about a foot from the basement ceiling the pipe inserts into some sort of black pipe collar...must be fireproof.
 
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Old 10-01-14, 06:08 PM
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I wonder if pictures would help us visualize and maybe get some ideas.

It sounds hopeless though.

Feel like digging? Insulate the outside.

the flue from the back of the boiler goes up and about a foot from the basement ceiling
According to national fire code there must be at least 18" clearance between any single wall flue pipe and any combustible surface. Sounds like you may not have that.
 
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Old 10-01-14, 06:34 PM
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As said pics will help... You can move the flue and change to double wall right from boiler..... Less clearances............
 
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Old 10-01-14, 06:40 PM
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If you can do as they suggested- upgrade the flue and increase the clearance, Thermax might be a good option. It's not fireproof, but it's Class A, rated to 250F and can be left exposed since it has a foil face. Seams can be taped with foil tape to create an effective air barrier. 2" Thermax would be best if you can get the space for it.
 
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Old 10-03-14, 06:13 AM
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I will post a picture later today. Thanks everyone for your thoughts so far. The clearance is two inches but there is nothing combustible. It is close to the poured cement wall and of course that is not combustible but this is the issue (not enough clearance) if I want to insulate. I thought about digging and about double wall pipe and the latter is looking better and better. I will add a few pix to show how the pipe changes to black about two feet from sheetrocked ceiling and how the single wall flue pipe goes into it. I also thought about rockwool and cement board but rockwool smells a bit when outside in the air (?).
 
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Old 10-03-14, 06:41 AM
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It's a shame to waste all that heat. How about an aluminum panel spaced 1 inch off the wall to reflect some of it back into the room? The reflection + air circulation around the panel might be enough to keep the wall from melting the snow.
 
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Old 10-03-14, 07:30 AM
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Pix

Name:  photo 1.jpg
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Size:  18.6 KBName:  photo 2.jpg
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Size:  14.3 KB
Here is hoping I was successful in doing the pictures as attachments and into the body of this message (first time I am trying!)
 
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Old 10-03-14, 02:42 PM
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I don't think that's up to code... as far as the 18" clearance to combustibles goes.

It appears to be a 'manufactured chimney'. That is, insulated double wall. Where that pipe comes out of the 'thimble' at the ceiling is where the actual flue pipe starts.

If you take a tape measure from where the black pipe starts and measure out 18" in all directions from that pipe I'm pretty sure that you're going to have stuff within 18".

That's 6" flue pipe? (pics make it look HUGE, like 8" ... but I know it can't be... can it?)

You could either go with double wall flue pipe for reduced clearance, which would act as a 'radiation shield' and keep the heat off the foundation, or install aluminum sheets on the wall spaced away about an inch or so in order that air can flow behind them as someone else suggested.
 
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Old 10-03-14, 06:02 PM
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Sorry. The pictures came out sideways. Imagine rotating it one turn clockwise. Ah I wish whoever installed the boiler and the single-wall flue had left 18 inches of space! It would not be so tight to get a sheet of anything behind it. Right now as it stands, I would have to probably cut a sheet in half to get something back there. I think you are right...to make this work, I need to double-wall that short section of pipe and then I could get a sheet of Thermex in there. Yes, the pipe is six inches. Thanks to you and everyone for the ideas. So now...where can I get a deal on double-wall pipe sections without paying an arm and a leg?
 
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Old 10-03-14, 06:06 PM
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Aluminum panel? Where can I get one...at HD or Lowes?
 
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Old 10-04-14, 10:55 AM
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I've never looked at HD or Lowes... don't know if they carry it, probably not.

I buy metals from time to time from a local fabrication shop... call around and you may find someone that stocks and will cut you a piece or two.

Think about Galvanized steel also, might be cheaper than aluminum. Perhaps one of your local HVAC places has some pieces they would sell you.
 
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