Many new garage doors offer good insulation built in. But many less expensive doors and older garage doors lack insulation. Without proper insulation, the house will lose a staggering amount of heat out the garage, even with the doors closed. When replacement doors are not an option, consider adding insulation to the garage doors. For a small amount of money and effort, the results are well worth it.

Hollow garage doors have empty channels inside. These can usually be accessed from the side of the door. It is important to consider the width of the channels before deciding on what kind of insulation to use. Reflective insulation can be easier to work with, but foam sheathing is available in higher R values. R value is a measurement of just how insulating a product is. Once the width and depth of the garage door cavities to be filled is known, simply go to the local home improvement store to compare the types of insulation and make a selection. A straight edge razor, or other cutting tool will also be needed. Don't forget to also pick up safety equipment such as safety goggles and heavy gloves. If fiberglass insulation will be used, a particle filtering mask should also be worn.

Cut the insulation to fit snuggly inside the door cavity. If they have been measured and it is determined that all of the cavities are the same size, then use the first well fitted cut of insulation as a template for further cutting. Foam sheathing is rigid and must be cut to fit exactly into the empty cavities. Reflective insulation can be manipulated as it is not rigid. If reflective insulation is used, cut it about one quarter of an inch larger than the cavity size. This kind of insulation will then bunch a little and create a better fill, thus improving the benefit of insulating.

Once all of the empty channels have been filled, foil tape over the exposed sides of the door to seal it up. The insulation portion of the job is now done. However, the garage doors will be heavier with the insulation than they previously were. Refer to the owner's manual of the automatic garage door opener and follow the directions to recalibrate the automatic opener to handle the extra weight. In the event that the existing garage door opener cannot handle the new weight, installing an opener that can is still less expensive than replacing the garage doors and losing heat through un-insulated doors.

If all of this seems like too much to handle, or work space is very limited, consider using a premade insulation kit. Many of these kits use materials that affix onto the interior side of the garage door without having to access the internal cavities. While these kits may be easier to use on some types of garage doors, it is still important to recalibrate the automatic opener to handle the additional weight. If problems arise, especially with the opener, consider hiring a professional garage door service to make sure that the door is still operational and safe.