What Kind of Insulation for Furnace Room?

What kind of insulation materials should I use to insulate the hot-air pipes and ceiling in a furnace room?
The house is about 5 years old with 6 inches of blown-in cellulose insulation in the walls and ceilings. The furnace room is on the second floor and has a finished drywall ceiling and walls. But the room is very warm during the winter and snow on the roof above the furnace room melts before the snow on the rest of the roof.
I've sealed the furnace pipe joints with mastic to stop hot-air leaks; but now I'd like to wrap the pipes with insulation and add a layer of ceiling insulation inside the room and maybe the outside wall too.
TKM
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wrote:

Good points. There is no system air return in the furnace room, so that's an excellent idea.
The furnace uses outside air for combusion. The walls are 2x6 construction as is the ceiling. 6" is the mimimum ceiling insulation thickness as the roof meets the eave right above the furnace room. In other areas of the ceiling, the insulation thickness is several inches more (as much as the contractor could blow in). The drywall is 5/8". The furnace room door (bathroom adjoining) is louvered. I leave that door open to increase air circulation
What I think I'll do is put a small flexible vent pipe into the air return plenum with the end of that pipe at the ceiling level. That will draw off the hot air rising from the furnace and pipes. But, I'd still like to know which insulation materials to use for those pipes and for another layer on the ceiling. The ceiling material, of course, should meet fire code requirements.
TKM
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There are several possibilities. See what your local DIY store has. Fiberglass bats (1") or so should do it. You can use layers if you want. There are other products available if you look around. Frankly I doubt if you are going to gain anything by insulating the ducts. Insulating ducts in areas where the air is conditioned is usually a waste of time.

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Joseph Meehan

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How about venting the room to the rest of the home? Is the air pressure in that room higher than or lower than the rest of the home? Assuming it is gas or oil fueled, don't allow the room to go to a negative air pressure, but you should be able to allow greater air exchange with the rest of the home.

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Think about it. The heat in the furnace room must go somewhere. If the room is too well insulated it will get hotter and hotter until the heat loss equals the heat from the furnace walls. This will cause the furnace to be hotter, maybe shortening the life of the motor. You might put a small opening in the inlet duct to draw house air into the furnace, making sure there is space under the door for the air to flow in.

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First check your local codes about the benefits of installing a return vent in a furnace room. It may not be legal because of the potential of creating negative air pressure in the room resulting in the flames not staying where their supposed to be in the furnace, and the possibility of drawing carbon monoxide and/or even natural gas or propane into the household air distribution ducts if there should be a leak.
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