Silicone or duct sealant is fine. But both need to be protected, coated, supported and sealed with aluminum foil tape, the real adhesive tape. However, first of all, the joints of the ducts (supplies and returns) must be solidified, since they cannot come off or slide or deviate in any direction. You must use quality duct sealing compounds to properly seal the ducts.
You should start with a silicone-based duct sealant that is easily applied with a putty gun. This sealant will cover cracks and holes and keep moisture at bay. I would like to know if there is also a suitable and safe caulking compound that I can use to seal duct joints. A complete inspection and proper sealing of the ducts can cover holes that could cause diseases and damage the air conditioning system.
I'm sealing some joints that leak into my basement ducts with aluminum tape.
