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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90 Discussions

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JessicaP194

20 days ago

I've been battling heat in my shop since I moved into my current home eight years ago. I live in SoCal, and my garage door faces west. The afternoon sun has always heated up the shop to levels that make me spend less time in the shop.

I added a mini-split HVAC, and that helped enormously. But in the summer, when the outdoor temps can get over 90 degrees (sometimes over 100), and the afternoon sun is beating on the garage door, my mini-split had no hope of keeping up, and shop temps would climb.

I insulated the walls and ceiling, and that definitely helped. But my mini-split was still no match for the summer afternoon heat.

So, I got a thermal imaging camera. I learned a few important things that have helped get the heat under control.

First, the uninsulated steel garage doors were acting as a giant radiator. I knew that, but I didn't realize just how much that contributed to the problem. On those 90 degree days with the sun beating on the door, the temp of the outside of the garage doors would get over 120 degrees. The inside of the doors would get over 110. Since my shop is a 3-car garage, that's a lot of heat! No wonder the inside of the shop kept getting so warm.

I bought those garage door insulation kits from a big box store like this https://mechanicguides.com/best-garage-door-insulation-kit/ (I think HD). That made a significant difference, but the doors were still a big radiator. Instead of the inside of the door registering 110 degrees, it would get up to the high 90s. That's a 10-15 degree drop, but my mini-split still struggled to take all that heat out of the shop.

A few months ago, I upgraded my garage doors to some of those R-18 super-insulated garage doors (with no windows). That has made an enormous difference. We haven't yet had any 90+ degree weather this year, but so far, the inside of my garage doors has stayed pretty close to the ambient temp in my shop. So, whatever heat the sun is putting onto the garage door's exterior is mostly not making its way into the shop.

People get fixated on seals. In some circumstances, bad seals can be the culprit. But keep in mind that the job of the seals is to keep the heat/cold in the AMBIENT air outside from getting inside. When you have a West-facing garage door and the sun is beating on your garage door in the afternoon, the ambient outside temperate is really not the problem. The problem is that the sun is super-heating the exterior surface of your garage door to a temperature that can be 20-30 degrees hotter than the outside air. That's a much bigger problem than bad seals. I'm not saying that seals don't matter; I am saying that getting as much insulation as possible on the surface of your garage door is much more critical than seals for controlling heat if you have a West-facing door and you want to keep your shop cool. At least, that has been my experience.

The thermal imaging camera also gave me some additional insights. I had extensive fluorescent lighting throughout the shop, and the camera showed just how much heat those were putting out. So, I changed to LED lighting. Enormous

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SteveB461

Question 6 months ago on Step 2

I used 1 inch. Looks like you have have used .75?

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SteveB461

6 months ago on Step 3

Great post. Live in AZ and it worked great. We need to REFLECT heat not retain/capture it. I did exactly what you said and with a 10k BTU cooler my south facing garage gets into the low 80s in the 112 degree heat.

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ClaudiaH41

11 months ago

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.

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KevinB508

11 months ago

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.

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rmathis1

3 years ago on Introduction

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.

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Greatpixrmathis1

Reply 2 years ago

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

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jasonweng

2 years ago

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
here?

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AtticFoiljasonweng

Reply 2 years ago

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.

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dougman

2 years ago

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.

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AtticFoildougman

Reply 2 years ago

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.

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cchubb

2 years ago

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.

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adam.hamilton.505

3 years ago

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

image.jpg
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JayB117adam.hamilton.505

Reply 2 years ago

Is the insulation making a difference? I live in the desert too, with a north facing garage door. Thanks!

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PennyT10

2 years ago

I want to close in the garage to make a family room with a tight budget. We insulated the garage very well when we built our house. Do you think this would work by doing this and not actually taking out the garage door, but not ever using it. I live in Georgia.

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AtticFoilPennyT10

Reply 2 years ago

Your best bet is to build an interior insulated wall inside the garage door. Then, if you (or the next homeowner) wants to use it as a garage, they simply knock down the wall.

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bupert

3 years ago

Bubble wrap sheet between door and insulation panel will create the dead air space you want and allow t

you to get flatter look without bulgeing foam to create this space

Is it normal for the insulation to stick out a bit? I purchased a kit from http://www.garagedoornation.com/products/garage-door-insulation-kit and I just want to make sure it's fine. I am also in Phoenix area. I submitted information for the energy credit on my taxes and I'll update once I hear back from the accountant. I'm hoping to get the energy credit too! :)

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kylegdsncdoityourselfer2015

Reply 3 years ago

The problem with insulating your door is you add weight. The door in the instructable is a 16x7 I weighs probably 160 to 165 lbs after insulation is added it will weigh 175 to 185. Without changing the springs out your door will crack a panel or opener will strip a gear. Also you only have a 7 to 8 lb margin of error to adjust your springs. This is a great source for garage door springs parts and awesome videos www.diygaragedoorpartsonline.com

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Love this idea and I'm doing it. However rather than creating the arch gap I think I'll use standoffs with some type of adhesive to give a uniform smooth look and eliminate the open air gap visible at the top of the arch. Thanks!