Is Insulating a Garage Door Necessary?

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Energy costs fluctuate over time, but with the overall trend always upward, homeowners are increasingly looking for different and additional ways to insulate the home and keep heating and cooling costs down. One area that is frequently examined is the garage—and specifically, the garage door. A garage that is attached to the house and shares one or more common walls with the home itself can definitely be a source of energy loss, so evaluating the garage makes perfect sense.

The garage door on an attached garage is often seen as a weak link in the thermal envelope on a home, and for good reason. In most homes, the garage door opens several times a day, exposing most of an entire wall to outdoor air. Because a garage door functions like this, it's tough to adequately seal and insulate the garage. Unless the garage door is rarely used, any effort to thoroughly insulate the garage often costs more in materials than you'll gain from energy savings.

Still, people often feel that adding insulation R-value to the garage door is warranted and necessary. And in a few instances, this may be true.

Methods for Insulating Garage Doors

Garage doors regularly open and close, often hinging or folding at several different points. Some insulation methods may not be long-lasting as the door continues to function. You may find insulation flaking or pulling apart. If you want to try an insulation method, perhaps as a temporary seasonal fix, consider these common garage door insulation methods:

  • Foam board insulation: thin, rigid, high-insulating value panels
  • Spray foam insulation: sprayed onto your garage door, but not the most effective method; the same kind of insulation sometimes sprayed against roof sheathing from the inside to improve the R-value in an attic
  • Cellulose insulation: must be sprayed onto garage door; provides much better results than spray foam, but it's the most expensive option
  • Reflective insulation: thin, rigid boards with reflective foil to deter heat; best for hot climates
  • Fiberglass insulation batts: least expensive insulation; best applied on the inside face of the door

New Insulated Garage Doors

If you are intent on an energy-efficient garage door, a better alternative is to purchase a garage door that is already insulated. Rather than a metal door, which conducts heat and cold easily, choose a fiberglass door with a foam core, which will help stop some of the energy loss from the garage. If you're planning on replacing your garage door, looking into an insulated model is probably a good idea. But it probably does not make financial sense to replace an otherwise good garage door with an insulated model just for the energy savings potential.

Insulate the Rest of the Garage Instead

Garage door insulation is of limited value anyway, given the other areas of the garage that are equally problematic in terms of energy loss. The floor of your garage is probably built on a slab, which means that it isn't insulated and is an ongoing source of energy transference. If your garage has concrete walls, these, too, are constant sources of transference. If you take the time and spend the money to insulate the entire garage, you may well be disappointed by seeing a very minimal improvement on your energy bills.

Rather than attempting to insulate the garage door and other components of the garage itself, a much more effective solution is to focus your attention on the boundary walls between the main house and the attached garage. By doing so, even if the temperature fluctuates inside the garage, it won't significantly affect the temperature inside your home or raise your energy bills. Here are the best ways:

  • Put insulation into the ceiling of the garage so it helps stop the loss of energy to the space above, where it may connect to the house attic or a room above the garage.
  • Add plenty of insulation on the interior wall of the garage that's shared with the house itself.
  • Eliminate air gaps before insulating by taking a can of low-expanding spray foam around the garage to seal all the gaps and cracks to the outside, especially along any windows.

The Exception

While most contractors will tell you to insulate the transfer points from the garage to the house itself, there are still times when you may want to further insulate the garage door, as well as the walls and floor of the garage. If you use your garage as a living space, rather than as a storage area for cars and other items, then you may be heating or cooling the area anyway, and the garage door may not operate much. In this instance, it does make sense to maximize the R-value of the walls, floors, ceiling, as well as the garage door.

This can be true of both attached garages and those that are detached and separate from the house. If you are supplying supplemental heat or air conditioning to a detached garage, you'll want to make every aspect of the garage as energy-efficient as possible. It has been shown that an energy-efficient R-18 garage door can keep the garage space about 12 degrees warmer in winter months and about 25 degrees cooler in summer. But remember that an energy-efficient double garage door costs somewhere between $1,500 and $2,000, so it will take considerable time to pay back the cost of the door in terms of energy savings. And it really only makes sense for spaces where the garage door won't be opened routinely to break the energy envelope.

Garage Door Insulation Kits

Another option where the garage will be used for living space is to insulate the door with a garage door insulation kit, available at home improvement centers. There are two types of kits usually available. A vinyl-faced fiberglass batting kit provides a decent R-8 insulating value for the door; two kits will cover a standard 16-foot-wide garage door. This type of soft insulation is taped to the inside surface of the door. Another option is to buy precut expanded polystyrene (EPS) rigid foam panels and apply them to the door. The panels are cut to length and snapped into the space between the horizontal rails on the door panels. This type of kit provides an insulating value of roughly R-4.

Air Sealing

Most people think of improving energy efficiency in terms of adding insulation, but the reality is that a significant degree of heat loss occurs because of air gaps where drafts occur. Insulating a garage will be of limited value if door gaskets, window weatherstripping, and other air gaps are still providing places for air to flow. Always seal these areas when you are addressing the energy efficiency of a garage.

Should You Insulate Your Garage Door?

If you use your garage as storage for your cars and other items, you're probably better off leaving the door alone and insulating the ceiling of your garage and the walls that are shared with the home instead. If you use your garage as a living space, however, it's probably worth your while to insulate the door as well as other elements of the garage. Make your decision based on your lifestyle and needs.