Measure the garage door panels and gather insulation material, tape, utility knife, straightedge, and cleaning supplies
Clean the inside surface of the garage door thoroughly and let it dry
Choose an insulation type suitable for garage doors, such as foam board, reflective insulation, or garage door insulation kits
Cut the insulation panels to fit each door section
Attach the insulation using adhesive, clips, or the fastening system included with the kit
Seal gaps around the edges and between panels with weatherstripping or foil tape
Avoid blocking hinges, rollers, tracks, or moving parts
Reinstall or adjust any trim pieces if needed
Check that the door opens and closes smoothly after installation
Add bottom seal and perimeter weatherstripping if needed for better thermal performance