Thanks for all the helpful response folks. I really appreciate them.

Spent some time last night researching different insulation brands / types. Come to find out, I have this in my basement. GE Insulation Foam

The previous owners left a good amount of similar cleaning & gardening supplies, and a bunch of paint cans. The spray can is not that old either, it has a production date on it.

Unless this brand is complete garbage, I guess I'll use this around the interior vent. I'll have to get some sealant for around the vent's exterior myself. Can't find everything in the basement I suppose.