You probably need to make some efficiency improvements for both your comfort while working and for the energy losses from the bedroom floor above it. If the builder installed an inexpensive, inefficient garage door, as many do, or it’s an older building, it’s likely the bedroom floor above the garage isn’t well-insulated either.
Before you invest in a new, efficient garage door, inspect your existing door. If it’s in relatively good condition and there are no significant drafts coming from the joints between the panels, consider installing a garage door insulation kit. Some kits provide an insulation value as high as R-8, but they won’t seal air leaks through the joints between the door panels.
Owens-Corning makes an easy-to-install insulation kit. It includes vinyl-backed fiberglass insulation batts, retaining clips, and tape. Cut the batts to fit the door panels. Apply strips of double-sided tape on two spots on each panel. Stick the retaining clips on the tape and push the insulation over them. A top clip snaps over each clip to hold the insulation securely in place.
If you decide you need a new door, material options are wood, insulated steel, insulated fiberglass, and aluminum/glass. Insulated steel or fiberglass will offer the best efficiency because of the insulation value and the rigidity of the door to remain airtight over its life.
An insulated steel door is probably the least expensive design to meet your efficiency and comfort needs. Some foam insulated steel doors, such as the Clopay Gallery Collection double-wide door I installed at my home, have insulation values as high as R-19. The foam inside the door can be either glued-in rigid polystyrene or blown-in urethane foam. Urethane foam has a higher insulation level.
When choosing a steel door, look for one with a thermal break separating the outdoor and indoor metal skins to reduce heat loss. This is not a factor on a fiberglass door. If you want glass in the door, make sure it’s at least double-pane, insulated glass or low-E for better efficiency.
Windstorm supports reduce wear and tear
Many insulated steel garage doors are “wind rated” for severe weather. Even if your area doesn’t have frequent high-wind storms, install the horizontal galvanized steel supports across the inner surface of the door if they were included with it. As the door rolls up to open, the edges are not interlocked to support each other. Without the supports, the panels may flex and crack over time.