As I was on top of a ladder, prying down the old suspended ceiling in our kitchen, I noticed a pleasant draft (considering how warm I was). It was blowing out of the gap between a dummy cabinet covering the furnace flu and the ceiling soffit. The whole house fan was blowing air into the attic, and it was coming back out that crack!
So what is a “legal” way to seal that hole? The flu is a double-walled steel unit, fed from a conventional gas furnace, ca 1972.
I had once tried to get to the area in the attic, but it’s so close to the edge in the 4/12 attic that you can’t really get there. So I figure I can pull the false back from the cabinet and work from there to seal it. If I can find out what’s legal as a “sealant”, in contact with the flu. Is drywall legal? Cement board? Sheet metal?
Replies
Uh, er, make that "flue".
No one has anything to say about this??
So, you think your flue has got the flu since it has chills from feeling drafty?
OK, Help me visualize this. Is the total chimney still there? or has it been cut off and discontinued? If it can ever be used as an exhaust again, it should probably be repaired as tho it is still being used for ####flue. but if you are just trying to seal against draft, you could squirt some expanding foam in to stop draft.
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The setup is basically like this, only from a GFA furnace vs fireplace:
http://www.thevictorianfireplace.com/duraventgasd2.htm
The problem is where the vent goes through the "floor" of the attic. This is complicated by a dropped soffit in the kitchen below, such that the passage through the "floor" of the attic is about a foot below the bottom cord of the trusses, making it that much harder to reach from above. There is a roughly 6" x 12" hole in the drywall there that the flue (and a draft air pipe) pass through.
The flue "chase" is a dummy (only about 6" deep inside) full-height kitchen cabinet. The furnace is in the utility room in the basement.
(Of course, the problem may be solved in large part by the fact that my ceiling project is turning out so well the wife is likely to insist on new cabinets to match.)
But unless and until we do new cabinets, I probably need some sort of "quick fix" that can be done in close quarters. Eg, something like stuffing fiberglass into the opening.
my literary skills were lacking or my translator had a hard time making the 3D visualization until you explained it al again and I read it two more times.
bob is right. That missing part is called a firestop spacer and it is listed in his link.
But since access is hard and the pipe is already in place, the spacer can't be installed now. You need to do this with sheet metal. Cut two "U" shapes to fit around from opposite sides and tack them to the attic floor, and use pop rivets or SM screws to lap them together. Then you can take some firestop caulk to seat it tight to the flue. Don't pack it with FG. There should be one inch of free space surrionding this flue pipe.
for some reason, I kept picturing a masonry chimney in my mind's eye last night, probably 'cause that's what most of them are around here.
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ou need a firestop:
http://www.thevictorianfireplace.com/duraventbvent.htm
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