I am looking for some advice on a few things related to sealing flu and air ducts off a sealed combustion gas fireplace... 1) Specs require inside joints of Duravent to be sealed with Mill-Pak. I know this is not a sealant/adhesive, so looking for advice on the best way to apply it to get a good seal on inside joints. 2) Specs do not require any sealing of outside joints on duravent, although I prefer to do it anyway so no room air is sucked in intake. Is any high-heat silicon sealant ok here? I do not think there is any code requirement for the red stuff... right? 3) I have two hot air ducts off the unit (plain old 6" rigid duct carrying heated room air to another location). Specs say no contact with combustibles within first 6 feet off unit. Thereafter direct contact is OK. I'd like to seal these joints. What can be used to seal the joints in the first 6 ft where no contact with combustibles? Also, specs say to insulate the ducts and make no restriction about first 6 ft. Is non-faced fiberglass considered a non-combustible and OK to use in first 6 ft of air duct off unit? Any feedback is greatly appreciated!