Is there a preferred mastic to use for sealing the outside of vents in an attic?
How about for work that may be partially on the inside of vents? I found a hack job in my house where the previous owners cut a hole in the bottom of a floor vent boot and used the hole to blow air to a vent in the basement (they didn't even use sheet metal to cover over the exposed insulation between floors! ).
For this job, I want to abandon the basement vent (totally unecessary vent). I was thinking of having the someone use sheet metal to cover over the hole that was made in the bottom of the boot and sealing the edges with mastic.
First is okay to have a decent amount of mastic in the air way? I mean will it break down and dust or off-gas or anything?
Secondly, I've seen types of mastic that say fiber reinforced. I am assuming this is fiberglass? I feel leery of allowing someone to use anything with fiberglass in it within the airway. Can we get away with using a non-fiber reinforced mastic?
I will be having someone come out to install a Lennox or April Air filter as well as fix the mediocre install of my new hvac so I will be discussing this with them. I want to be informed.