insulating a furnace flue - it's heating the attic
There was a post similar to this back in December, but it only addressed blocking the airflow around the B-vent, where it comes out of the floor. My problem is a bit different...
I've been working on insulating my attic and discovered that my furnace flue is giving off a lot of heat. This is essentially heating my attic which here in the Utah mountains is contributing to huge ice dams.
My furnace flue is in a b-vent, from what I can tell, except for a 4 foot stretch where there is no B vent. The B-vent comes out of the floor of the attic, then stops. There's a section of B-vent attached to the roof. In between there is just a simple single wall vent. It looks like the flexible vent that comes out of a clothes drier - not sure what it's called. You can see this flexible vent coming out of the b-vent, go up 4 feet and then go back into a b-vent out the roof. It's this 4 foot section that is giving off a ton of heat.
I had the people out who installed the furnace two years ago and they said it's up to code this way. Is it?!?! They got belligerent when I questioned it. I read somewhere that flues in unconditioned spaces *must* go through a b-vent. I would assume that it would mean the *entire* flue.
Even if it is up to code to have part of the flue not in a b-vent, how do I insulate this 4 foot section? The problem is that the b-vent coming out of the floor and the b-vent attached to the roof are offset by about two inches, so the HVAC people couldn't run the b-vent all the way up. Isn't there some kind of flexible, insulating pipe that could be put in to accommodate the offset?
Any help is appreciated!