3 Steps & Most EFFECTIVE Way to Insulate Your Garage Door to Reduce Heat Gain





Introduction: 3 Steps & Most EFFECTIVE Way to Insulate Your Garage Door to Reduce Heat Gain

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Insulating a garage door is worthwhile for many reasons. The main reason someone might want to insulate the garage is simply because they spend time in there. Be it woodworking, automotive tinkering or lifting weights on a home gym - these are all reasons why you would want the garage to be more comfortable when you're inside it. Opening a window or running a fan can help move air, but it won't stop heat from coming in so it does little toward creating a comfortable space. We are going to show you the method that is hands-down the easiest way insulate the garage door (the main culprit in heat gain) so you can be closer to a more comfortable space for whatever you're doing in there.

Bonus: creating a more comfortable space for a garage that is attached to the house can usually mean the room on the other side of the garage is a bit more comfortable too!

Step 1: Step 1: Gather Your Materials

For this installation you will need the following items:

  • 4 sheets* of foil-faced foam board (pictured here is Perma"R" brand but there are several other brands available such as Johns Mansville, TUFF-R or you can make your own foil-faced foam board at home.)
  • A knife/blade to cut the foam board
  • A measuring tape or metal yardstick

*4 sheets of 8' x 4' foil-faced foam board will generally be enough to do a standard 2 car garage door.

Step 2: Step 2: Measure and Cut

After you have gathered all your materials, measure the size of each panel frame in the door (the metal that frames the panel). Then, add about an inch to the shorter dimensions and cut the foil-faced foam board into the rectangles. The reason you add an inch to the height of the rectangle is because you want the panels to be slightly larger than the actual framing on the door so that they are convex and curve outward when you put them in. This step is absolutely critical because if you don't create the air gap, then the foil will NOT work as a radiant barrier and you'll just be wasting your time. You can read why the radiant barrier foil requires an air gap to work, so if you just put the foam in flush against the door this method is not nearly as effective as if you create the air gap. Remember, this method is to primary reduce summer heat gain. There will be some benefit in reducing heat loss, but the big impact it to reduce heat from the sun beating down on the door.

When it's time to place the foam board into the frames, situate the foam so the foil side is facing the garage door and the small air space you created from the convex shape. Start by inserting the top edge in first, then "pop" in the bottom edge. The panels should be convex and have a curve outward that is visible when you look at them from the side (see the image above).

Step 3: Step 3: Finish It Up

Continue repeating step 2 for the rest of the panels.

Tip: save yourself the headache of wasted materials and measure each panel individually, you can't always assume they will all be the exact same size!

When you're done, you'll have the benefit of a radiant barrier as your first line of defense right after the metal door, and then you'll have the foam board to help slow down the little heat that makes it past the foil. The result? A brighter, more comfortable garage door that is properly insulated to help you keep radiant heat out in the summer.



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I think he did a great job BUT what I want to know is how he built that Great shelf above the garage door track? Please, post instructions for that. I really want one of those.

It's a nice idea, but did anyone consider the writing on the Perma board in photo 1? This foam cannot be exposed to flame as it will produce toxic gas that will knock you out in a fire.

One suggestion that worked for me was using a junked bread knife for my cuts. Specifically, heating the blade on a campstove allows you to cut the material without little white foam dots getting everywhere. So what the vapors are probably bad, but it makes cutting the boards quick and clean.

I saw one installer using an old electric carving knife that cut through the foamboard like butter.

t looks that the curved foam board leaves 2 gaps on its 2 sides that the
air is not sealed between foam and door panel. Air works as good insulation
only when it's not flowing. Otherwise, what's point of installing foam
boards (we've got plenty of air in the garage ). Am I missing anything

The purpose of the method described is to REFLECT radiant heat to keep the garage cooler, not to act as an insulation. This is basically like putting a solar screen (reflector) in the window of your car.

OK, I want to clear a few things up. My wife owns a garage door spring manufacturing company. I referred this question to her. If the door spring is a torsion spring, AND it is not a high lift door, an installer can add tension to the spring by putting more turns on it. DO NOT ATTEMPT THIS YOURSELF, it can result in serious injury or death! If it is an extension spring, it WILL need to be replaced with a stronger spring (an extension spring lifts what it lifts, and cannot be modified outside of a small margin). If the insulation weighs 15 lbs, it is outside the margin of the springs. If you are using an operator, it will MASK the weakness of the springs for a time, but will surely result in your operator wearing out much faster. My father had a similar experience with painting (it's surprising how much weight 2 coats of latex add to a door) and insulating his garage door, the operator was struggling very noticeably, and after she fixed him up with the proper springs it operated like new.

The weight of the foam is usually between 5-8 lbs do do this project. I fully understand this would be concern if you were adding significantly more weight, but this amount will normally not require any adjustments.

I would add one small detail to your otherwise great 'ible. When you measure for the length of each piece, include the full width of the door panel, including inside the end channels. Then, right before installing, cut each in half along the width, right in the middle. Try to keep that cut really clean. Then, for each piece you can bend and install the left side, slide to the left, bend and install the right, slide to the right and they will snap into alignment. A short piece of tape will dress the joint if the edge is ragged, but it's not required.

I would also reduce the oversize width to 1/2" instead of 1". That will still give a good curve for air gap and still a tight fit. The ends should then fit under the vertical channels. You might need to experiment a little on the first one to get the right oversize.

At least you put the foil side on the correct side. So many of these DIY posts miss that part.

I just simply bought two of the garage insulation kits from Home Depot. They have slits for air on the inside and fit perfectly into the slots in the garage door after a little trim. I live in Phoenix and am just now installing. I hope it works well. It's a North facing garage, but it gets hot in the Summer. I have a port-a-cool 3,000 that I will run in the garage. It hopefully will keep temps down to around 85 in the garage. Time will tell. Here's a picture of one of the panels installed. I messed up the cut so there's a little gap. I plan on filling any gaps with a spray insulating foam when all panels are installed