How much can an insulated garage door help with energy efficiency?

Insulation makes the most difference if your garage shares a wall with living space, like a bedroom or laundry room above or next to it, or if you use the garage as a workshop. An insulated door limits that heat and cold transfer, so your furnace and air conditioner do not have to work as hard on the attached rooms. R values for garage doors typically range from about R 6 for single layer polystyrene doors up to R 18 or higher for triple layer polyurethane doors.