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

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

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

Picture of 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

Picture of 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

Picture of 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.


KevinB508 (author)2017-11-29

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.

rmathis1 (author)2014-11-17

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.

Greatpix (author)rmathis12016-11-10

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

jasonweng (author)2016-07-25

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

AtticFoil (author)jasonweng2016-09-13

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.

dougman (author)2016-09-10

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.

AtticFoil (author)dougman2016-09-13

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.

cchubb (author)2016-08-23

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.

adam.hamilton.505 (author)2015-05-04

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

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

TimR123 made it! (author)2016-06-04

60 dollar garage door insulating project a success! R10 and all about 1 hours work. 2 sheets of light weight double foil coated Thermasheath RMax 1.5" thick did the trick. Oh, and some aluminum tape to secure and dress the edges.

PennyT10 (author)2016-03-06

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.

AtticFoil (author)PennyT102016-03-07

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.

bupert (author)2015-10-21

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

doityourselfer2015 (author)2015-09-18

Is it normal for the insulation to stick out a bit? I purchased a kit from 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! :)

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

ThingEngineer (author)2015-02-01

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!

Broom (author)ThingEngineer2015-03-26

Yep, that sounds like the better idea. Foam double-sided tape, cardboard strips, a bead of silicone or liquid nails allowed to dry (to ensure a standoff) followed by a wet layer to attach the foam blocks - anything to create a 1/16" to 1/4" gap should work.

jrbuilta (author)2014-11-16

This looks clever and fairly easy. Only question I have is whether it would be good to attach the foam panels with a few dollops of Construction Adhesive, such as Loctite.

21bose (author)jrbuilta2014-12-06

You can actually attach the insulation on the inside, which is what I did. It creates a sealed air gap.

AtticFoil (author)jrbuilta2014-11-17

If the tension is good, you should not need any adhesive.

gary.918 (author)2014-11-18

I get a lit of cold air from in between the door joint any ideas on that

21bose (author)gary.9182014-12-06

Use the thinnest door or window weatherstripping you can find. It worked pretty well on the door I did this to in college.

john.west.96343 (author)2014-11-23

Tried this one year. Don't remember the R value but it had pink foam inside and 3/4". It fit perfectly into the Door Panel Frame troughs. In TX the Garages have no insulation over them so in the summer they heat up easily. And in the Winter the doors have a southern exposure and it seemed like the insulation kept the doors from warming the Garage and kept the light out of the windows. It surly did look cool though a it did not add much weight to the doors. Hope someone else has better results.

roboticage (author)2014-11-22

Nice! But here in Romania (Europe) we have to protect against cold not hot days and nights, and in my case I mounted same kind of foil but with the metalic face inside and without air gap, glued on the metallic door panels. Works like charm with the condition to have also a rubber or foam gasket across door contour. Like!

vladivastok (author)2014-11-20


MamaSmurf5000 (author)2014-11-16

My ex put buffalo board on the door to insulate it. I did end up having a repairman coming out to adjust the tension when it quit working because of the added weight. I am thinking that there would have been a lighter option to use but he was cheap.

Vyger (author)MamaSmurf50002014-11-19

Depending on how long ago it was foam would have been cheaper so he might have done the more expensive project. But that board doesn't have much R value to it. At least he tried.

Jason39 (author)2014-11-16

Nice project! I live in Niagara Falls NY where it is very cold so I am super excited. I also need to blow on insulation into the attic then the mancave will be complete!! Thanks

Vyger (author)Jason392014-11-19

Like the author said this is not really a fix for cold.

The R value of that foam is probably pretty low from the looks of it.

I live in Montana and when its 20 below thin foam like that will actually get covered in frost. The door itself is totally wrong for a cold climate. Among other things the metal its made of will act like a heat sink and draw the heat out and radiate it away. There needs to be a break between the metal faces. if you look closely at a steel entry door the steel does not wrap around the door. There is a small gap between the metal from the different sides. This short circuits the flow of heat from the heated side to the cold side. You can do an experiment to verify this. Scrape some of the paint off and use a piece of aluminum to connect the two sides together. Then when its cold out use an infrared thermometer and take temperature readings from all over the inside door surface. You will find that its is markedly colder where you put the thermal short.

For a cold climate you need to get door panels that have an insulated core and thermal isolation between the front and back. Adding 2 inches of foam to the panels on the inside would slow down the heat loss but you would still be loosing a lot through the metal frame. Keep in mind aluminum is used for heat sinks because it transfer heat so well. A wood door would be much warmer and you could insulate it.

AtticFoil (author)Jason392014-11-17

Please take a look again. The main objective of this method is to keep heat OUT. To turn your garage into a mancave, you will want to bulk up the doors with insulation and make the garage as airtight as possible.

gearup500 (author)2014-11-12

Wow, I never thought of insulating a garage door. The problem is will it stop the garage door from opening? This would be a major problem if you want to use the garage for what it was originally made for. Otherwise this is a project worth doing! Nice work!

AtticFoil (author)gearup5002014-11-17

The panels are cut to fit inside the panels. The door will still function normally.

gearup500 (author)AtticFoil2014-11-18

Ooohhhh, Now I know. That's pretty cool! I'll tell my neighbor who has a garage about this!

seamster (author)gearup5002014-11-12

I did this with my garage door, and the foam just sits inside the existing metal panels (doesn't obstruct the hinges or anything.)

The door still works just like normal, but now the garage stays toasty!

gary.918 (author)2014-11-18

I get a lit of cold air from in between the door joint any ideas on that

1hotpilot (author)2014-11-18

This approach will aid somewhat, in my opinion, but as a Home Inspector this project is missing an important issue with the curved gap left at each end. Thermal air cycling will occur with any gap in insulation. The Air on the exterior side of the foam picks up the outside temp & the differential temp with the Garage interior allows convective flow replacing the warmer with cooler. This is true with gaps in your attic, wall, or flooring insulation as well. In the winter the Warm interior air will replace the Door's exterior exposed cooler air via the cooling air falling relative to the warmer interior air. Sealing without allowing any condensation to form between the panels however is another problem to be solved. (condensation will oxidize the metal door over time)

There is actually another foil face already in place on the door that is being ignored. It is the original metal door skin (its just covered in paint). My preference is to totally seal non faced foam to the door's exterior & fill the whole door cavity(s) with foam (if you can afford it). Sealing the horizontal gaps between panels with flexible strips also helps. Definitely more materials but you get by without needing the foil faced material.

I've been in my home for 25+ years & perfecting the door edge sealing; top, bottom & sides, from air infiltration is just as important as adding insulation to the metal skin. Sealing homes & garages too tight however, has it's own consequences. Nothing is ever done without it affecting something else.

astrong0 (author)2014-11-17

MMMM them metallic orange shorts! Those are nice.

emachine56 (author)2014-11-17

The foil face goes toward the cold side-when this stuff is installed on a house. The foil is ALWAYS placed pointed away from the interior or the structure. The foil acts not only as a radiant but also a vapor barrier as well preventing moisture outside from transferring to the inside. The problem in this arrangement is that there is nowhere for the inevitable condensation to go. Cold out side, warm inside (or vise versa) means one side will condense moisture in the air. The air gap provides for an insulative dead-air space but only when it is a true dead air space. To accomplish this, the ends of the bowed foam board would have to be sealed. Maybe making arches from the foam to match the bow in the foam and using HVAC metal tape to seal the joint and construction adhesive to hold it to the door frame. You could also place a solid Tyvek moisture barrier to the door system to block moisture from outside air. I used Tyvek along with poly faced (one side) fiberglass blankets used in prefab metal buildings. At 8" thick you get plenty of R-value and it can be taped in place with HVAC tape (there is a special white type for this stuff but its expensive as all get out) the edges of the blanket are taped directly to the frame of door allowing for full articulation for sectioned roll-back doors with an opener or cantilever doors as well. Covering the entire door as a single blanket would be better because it eliminates of the heat/cold transfer effect on the exposed metal surfaces. The tape has stayed in place for 6+ years according to the current owner. This is a really good idea, though and nicely executed and aesthetically pleasing. I guess the bottom line is if it works for you, then it works! Thanks for sharing and keep it up.

AtticFoil (author)emachine562014-11-17

I get what you are saying. Sealing up the different ways you mention will help reducing heat loss in the winter. However, the general purpose of this post was a Quick and EASY way to reduce heat gain. As for the moisture concern. Just because there is a temperature difference does not mean there the will be moisture. You must have relatively warm-moist air come in contact with a cold surface. The key word being "relatively". Since the garage isn't a living space it tends to be much drier then the interior. Unless you are storing a bunch of plants (moisture source) in your garage, moisture condensation on the foil should not be a problem.

emachine56 (author)AtticFoil2014-11-17

Yes, it is indeed a quick and easy way to reduce heat gain. I tend to overlook the fact that I live in the deep south where humidity is like a family member; up close and in your face all of the time. I was just thinking if you are reducing heat gain the extra steps to accomplish heating/cooling loss might be worth someone's time. You gave us a great example that will inspire a lot of ideas and rethink some old solutions. Great job!

tak44 (author)2014-11-17

I did this two years ago slightly different (works wonders by the way) I put on radiant barrier by it's self (useing spray addhesive) then I cut little 1x2 spacers out of foam board glued them to the fitted pieces then after the glue dried glued it to the radiant barrier sealed it with some caulk. then pow 20 degree change. Note My garage door opener moved slower after but I just frankenstined a 1HP motor in to it now it's got power to spare.

Dead Planet (author)2014-11-16

Another way of saving the headache of wasted material is, after you've cut the first, try and see if it fits properly in all other places. If so, go ahead and cut them all, if not, you'll need to measure then ones that don't fit and cut those individually.

pattymadeit (author)Dead Planet2014-11-17

Brilliant! I see this tip applying to many projects! Thank you! :-)

Dead Planet (author)pattymadeit2014-11-17

Well, you're most welcome. :)

cfuse (author)2014-11-16

Can I ask about the floor treatment visible in the first picture?

srilyk (author)cfuse2014-11-17

If I had to guess - it looks like the kind of tile floor that you find at your typical big box retail store.

If you're not too picky you could probably find a good amount on the cheap at a Habitat ReStore though it's unlikely to match (unless you're lucky!)

AtticFoil (author)cfuse2014-11-17

Don't have any info on floor treatment. This picture was provided by one of our customers.

pattymadeit (author)2014-11-17

Well, AtticFoil .... you have certainly started a conversation here! Wow!

All that aside .... I'd like to say .. I think this project is FAB! We live in Arizona, in a house that faces East - so our garage door gets full sun for most of the day. Living room is right next to garage. I think this project could help us limit some of the heat in both rooms - and that's always a good thing during the summers here in HOTzona! Thanks!

AtticFoil (author)pattymadeit2014-11-17

Thanks for the comment. Installing radiant barrier will help significantly - even for morning sun. Once you see what it does to your garage, it won't take much convincing to do your attic too - same exact concept. Texas, Arizona, California and Florida are our best areas just because the sun is always pumping radiant heat into the homes.

About This Instructable




Bio: The best double-sided perforated aluminum radiant barrier foil insulation available; AtticFoil® blocks 97% of radiant heat. Radiant barrier AtticFoil® acts like shade: the more coverage ... More »
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