Our seal of approval on these top spots to seal-
“Common air leakage points to check and seal include:
The areas around plumbing, electrical, and duct work in exterior walls.
Any chases open to spaces like an attic.
Gaps between interior and exterior walls and ceiling sheetrock.
Any sheetrock areas, including between interior and exterior walls and where sheetrock is sealed to the subfloor.
Openings around windows.
Floors, including cantilevered floors and band joist areas in floor systems.
Kneewalls in cape-style structures.
Joints between existing buildings and additions or modular buildings.”
https://www.nationalgridus.com/Long-Island-NY-Business/Energy-Saving-Tips/Insulation