Inspect the garage for air leaks, moisture issues, and damaged surfaces
Seal gaps and cracks with caulk or spray foam
Weatherstrip the garage door and any entry doors
Install an insulated garage door or add insulation panels to the existing door
Insulate the walls with fiberglass batts, rigid foam boards, or spray foam
Insulate the ceiling or roof if the garage is below an attic or exposed roof space
Insulate the garage floor only if needed, using appropriate floor insulation materials
Cover insulation with drywall or another approved fire-resistant finish where required
Insulate around windows with weatherstripping, caulk, or window film
Add an insulated threshold and door sweep to exterior doors
Check and upgrade ventilation as needed
Protect plumbing and electrical components before insulating
Verify local building code and fire-safety requirements
Test for drafts and thermal leaks after installation