How to Insulate a Garage Door

If you have an attached garage with an uninsulated garage door, it's costing you money in both winter and summer.

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Studies done by garage door manufacturers prove that an energy-efficient R-18 insulated garage door can keep your garage about 12 degrees warmer in winter months and about 25 degrees cooler in summer. That reduces energy loss along the insulated walls and ceiling. A new R-18 garage door costs about $1,400 (installed price for a two-car garage), so it really doesn't pay to replace yours based on energy savings alone. You can, however, add insulation, doorstop weather stripping and a new bottom seal to your existing door to gain some savings and comfort. You can complete the entire job in about four hours for less than $200. Just buy the materials from any home center and gather up a utility knife, tape measure, straightedge, saw, dust mask, and a hammer and nails. Here's how to do it.

Types of Insulation To Buy

There are two types of garage door insulation kits well-suited for a DIY garage insulation project. An R-8 vinyl-faced fiberglass batting kit provides a relatively high R-value. It takes two kits to insulate a typical 16-ft. wide garage door.

Alternatively, you can buy precut R-4 expanded polystyrene (EPS) panel foam. Just cut each panel to length and bend and snap it into the horizontal rails on your door. However, at R-4 per inch, EPS has the lowest R-value. If you live in a moderate climate, that may be enough and could be cheap insulation for a garage.

If you’re willing to do a lot of precise cutting, you can achieve a higher R-value, up to R-9.8 with 1-1/2-in.- thick foil-faced fire-rated extruded polystyrene (XPS). Unfaced, non–fire rated XPS rigid foam should not be used for insulated garage doors. It’s extremely flammable and when ablaze, yields toxic fumes.

Next, buy enough doorstop vinyl weather stripping to seal the top and sides of your garage door. You’ll also need a new vinyl bottom seal to fit your existing track, or buy a new track if yours is damaged.

Project step-by-step (8)

Step 1

Measure, Mark and Install the Retainer Pins

  • Measure to find the spot 12-in. from each edge of the panel and midway between the horizontal rails.
  • Mark the location. Then peel off the adhesive backing paper and press the retainer pin base onto the panel.
  • Install two retainer pins in each panel.

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Step 2

Cut the Batting

  • Roll out the batting with the vinyl side down and mark the cutting lines.
  • Place the batting on scrap plywood. Then compress the insulated garage door with a straightedge and cut with a utility knife.

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Step 3

Lock the Batting In Place

  • Line up the insulation so it’s centered in the panel and push it against the retaining pin until it punctures the vinyl facing. Then push the retaining cap over the pin until it snaps into place.
  • Start by washing each door panel with household cleaning spray and rags. Then rinse the areas with clean water and let dry.
  • Measure the height and width of each panel and add 1 in. to the length and width when you cut the batting to size for a snug fit. Panel sizes may differ along the door, so measure each one as you go rather than pre-cutting all the panels based on one measurement.
  • Fit the cut insulation into the panel with the vinyl side facing into the garage. Then secure it to the retaining pins. Repeat until all the panels are insulated.

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Step 4

Mount the Doorstop Weather Stripping

  • Place the doorstop against the top and side jambs so the vinyl weather stripping is at a 45-degree angle.
  • Temporarily secure it in place with nails pounded in only partway.

Step 5

Readjust to Accommodate Door Movement

Apply pressure to the door to simulate the effect of a strong wind. Then move the doorstop inward to maintain a good seal. The gap may not be the same in every location along the sides, so check it in several spots and readjust accordingly.

If the door has too much play to adjust the doorstop properly, or you can see light through the doorstop weather stripping, replace your existing hinges with spring-loaded versions that press the door against the weather stripping at all times.

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Step 6

Install a new bottom seal

Uncrimp the bottom seal track slots

Jam a fat-blade screwdriver into the crimped area and twist to gently bend out the aluminum track. Repeat on each end of the track.

Fixing Garage Doors

Step 7

Slide In the New Bottom Seal

Slather some dishwashing detergent onto the slots along the bottom track or spray them with silicone. Then insert the vinyl seal and pull it into place. Cut off the excess vinyl with a utility knife and crimp the ends of the track with a pair of pliers.

Most steel doors have a track along the bottom to hold a vinyl seal. The vinyl can harden from sun exposure and crack or break off in sections, letting in cold air. Installers usually crimp the slots at each end of the track to retain the seal. Open the crimps and slide out the old seal. Then install the new one.

Step 8

Test the Door

A properly balanced garage door should stay in place if you lift it part-way and let go. However, insulation adds weight to the door, and that may throw off the balance. If your door falls after you let go of it, hire a garage door service company to readjust the spring tension. Leaving the door in an unbalanced state can damage your garage door opener.

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