Insulating gas furnace warm air vent

Feb 13, 2007 11 Replies

Hi,



my gas furnace sits in the laundry room in the basement and there is a lot of heat that comes off the pipe the sends the hot air up into the house. I went to HD and asked about wrapping some form of insulation around the pipe. I was first told to use batting wrapped in plastic. Thought this was not going to work given the amount of heat that comes off the pipe. Of course I wasted money on that after seeing the batting turn brown and fall off the pipe (had it taped on with heat resistent tape). Went back and someone else provided me with a foil wrap that sandwiches bubble wrap - I think it had an R rating of 4. Went on easily but as soon as the furnace kicked on, the bubble wrap shrunk and is now just a piece of foil wrapped around the piping. Im starting to think this isnt meant to be. I have only found stuff online that talks about insulating the heating ducts but nothing that provides any info on insulating the actual pipe that comes out of the top of the furnace. Is there such a thing?



Thanks.



Traveller



so far, it sounds like you are in the try outs for a Darwin award.

First identify, and distinguish, the flue and the duct. The duct shouldn't get much hotter than 150 degrees F, so there are several choices of insulation available, like fiberglass.

But if you melted the "bubblewrap" (by the way, that's designed for radiant barriers, not for what you did with it), I suspect you wrapped it around the flue (despite your saying it goes "up into the house," which the flue had better not). That can get a lot hotter. You should probably leave it alone.

Sounds like you're insulating your FLUE pipe...

Sorry slick, but foil/bubble/foil or foil/bubble/bubble/foil **IS** and CAN BE used for insulating supply/return ducts.

post a link to the UL approval.

By code, it cannot be used on interior duct surfaces, Duct wrap yes, duct liner NO.

I know of a very large duct cleaning company that installs the product inside airhandlers and RTU's after performing their cleaning services. Does not meet code in these applications.

Exterior... as he was talking "insulating around the pipe"

I still see alot of insulated flue pipes. Carrier has a mid vented with cvent to the liner. They put an insulated aluminum jacket around the cvent. I have started pulling alot of them off since discovering rust and corrosion at the vent connector. I see alot of cracked cells in carriers now, this is what led me to find the rotted flue pipe. New installs use bvent now, and even the latest cvent is no longer insulated. If you want to save money ditch the 80% and get a high efficiency. Insulating the flue pipe isn't a good idea.

-Canadian Heat

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Call a pro before you blow yourself up (or burn yourself down).

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