Instructables
Picture of DIY Attic Radiant Barrier
How-to for a cheap homemade radiant barrier for your attic. Radiant barriers battle the problem of emissivity in attics. When the sun beats down on the roof the shingles store energy then slowly gives that energy out in the form of radiant energy. So if you had a widget that could reflect that radiant energy away from the ceiling and back into the roof you could essentially reduce attic temperatures, therefore reducing your air conditioning load and save MONEY.
 
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Step 1: Items and Tools

To make the radiant barrier you will need a small list of easy to find items. This list started me out and I made 240 square feet of radiant barrier. The limiting factor is the spray adhesive. The can says that it coveres 220sq.ft. but I was using double that rate. This made approximately ten 12'X2' (24sq.ft.) lengths.
Parts:
1 Roll 36" X 33.3 yards painters Masking Paper (hardware store)
2 rolls of 12" X 75' generic aluminum foil (grocery store)
2 cans of 3M Super 77 spray adhesive (hardware store)
Tools:
Tape Measure
Broom
Razor Blade
Staple gun w/staples

Step 2: Make the radiant barrier

Picture of Make the radiant barrier
This is easy. Roll the paper out into predetermined lengths. I used 12 ft because that is what my attic needed. Tape the starting end down with masking tape if you like. Spray the adhesive to the masking paper in a 2ft wide pattern. Then roll the aluminum foil out starting with the left roll and over lap 1/16th" with the second roll. When you reach the desired length cut the now finished radiant barrier, leave the excess 1 ft until installation. I then used a broom to clean and press the foil to the paper.

Step 3: Install the radiant barrier

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Installation kindof sucks if your attic is tight or installation is during the heat of a summer day. MAKE SURE FOIL FACES ROOF! My method was start at the top leaving at least 18 inches of space. Then staple my way down starting with the side that does not contain the excess paper. I stapled at about 6in intervals. After both sides are stapled you can then remove the excess with a razor blade.

Update, monitoring my attic temps for a few weeks. I've been measuring temps at 2 heights in the attic. 1st location just above my insulation with a wired probe, still hovers about a degree over the day's high temp. 2nd location is 2ft above the attic floor, more of an average of where my hvac ducts are located. These temps max about 8 degrees above the days high temp. The differential is less on a milder day in the mid 90's. We have had a 100F day, 101 at the 1st and 108 at the 2nd. Attic temp seems to cool down pretty fast, mid 80's by sundown.

I have also done the kitchen foil attic barrier. I'm surprised this is the only place I found discussing it on the web! My attic already had paint on barrier on the underside of the roof decking. I wanted foil to help channel the heat up and out the ridge vent. I used Heavy Duty Reynolds wrap, its twice as thick as the regular foil. I double folded the end, stapled it to the joist and rolled it out across 6-8 rafters at a time stapling it along the way. I started a few feet from the eaves and ended about a foot from the ridge vent. I have one gable vent and no soffit vents. I have been measuring the temps at the top of the insulation for a month now. It has been consistently with in 1 degree of the outdoor high temp. Highest temp so far this summer has been 97F! I have a theory the solid aluminum foil might do a better job reflecting than the commercial barriers because they only consist of a super thin mylar film of foil. Either way it works great for just a few bucks!

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My attic on another web site. Yes I did receive their foil for free. I haven't installed it yet. It will probably go in a different attic.

http://www.insulationstop.com/radiant-barrier-blog...

rcg403 years ago
While hemming and hawing I decided to buy a remote thermometer (10 bucks Walmart) and put the remote in the attic and the reader in the hall. Hohum, hohum, the temp in the attic is higher.
So I put some money in the mix. I started logging the following:
time, inside-temp, outside,temp, attic-temp, KWHRS from meter.

For me to stay 77 inside, while it is 98 outside, and 121 in the attic, the KWH reading is higher.

Tomorrow I install radiant barrier. Next week, I will have some numbers
kkuepker rcg404 months ago

I know this was a long time ago, but did you ever get the 'AFTER' data for installing the radiant shield?

rcg40 kkuepker4 months ago

Right now ,31-May-2014 4:20 PM CDT it is 93 outside, 102 in attic, and 77 inside.

AC people who serviced the AC last year, said it was almost delightful since they did not have to alternate going up and down to take breaks from the heat.

tradergordo6 years ago
I'm very interested. But would have liked to have seen some good controlled before/after testing. I'd also like to know why you leave the gap at the top? For example it looks to me like the heat would just reflect back to the roof underlayment, generating a lot of heat in the air space between the barrier and the roof which would then just rise to the completely open top and fill your attic with hot air. I guess this would not heat the attic floor as much though? I don't know, my attic floor is completely covered with insulation - the attic can get extremely hot but the room ceilings below my attic don't get that hot - I'm kind of wondering if I would get any benefit from this or not? And how about another idea - couldn't you GREATLY simplify the whole thing but just stapling aluminum foil directly to the roof supports horizontally across the entire attic? You wouldn't need to do anything with paper, cutting, gluing, etc. You might need some special heavy duty foil though, not sure - but you'd definitely want to be very careful when doing the stapling. Perhaps it would be better to use silicone sealant beads instead of stapling? Come to think of it, that might be a really good idea. Silicone sealant is very cheap ($2-3 a tube) and can withstand temps up to 500 degrees F. It bonds to most surfaces and then you wouldn't have to staple anything. Just some thoughts...
crowdjs (author)  tradergordo6 years ago
foil by itself would be great but foil at the store does not have good tensile strength and thick foil with good tensile strength would be very expensive. The paper gives the right amount of tensile strength needed.
My guess is that most people don't need the extra tensile strength unless the attic is being used as a living space or something - there isn't anything to tear it. But if you wanted to, you could get a roll of saran wrap of the same width, and put the two together so they unroll together, that would give you enough extra strength, but still low cost and ease of installing.

But after reading the site that was linked here (http://www.ornl.gov/sci/roofs+walls/radiant/index.html) it seems I will probably not get any savings from this, and most people would probably be better off just putting in more insulation. I'd measure your actual ceiling temperatures before going though all the work.
I actually started putting foil before the summer made it unbearable to be in the attic for more than a few minutes at a time. I placed a thermometer directly below the area where I put foil and noticed a drop of about ten degrees.

The foil I used was purchased from Sam's, restaurant grade heavy duty Reynolds foil. It's a pain to work with, but once stapled, it won't move.

Also, if I stand directly below the unprotected area, I can feel the heat on my face, whereas under the foiled area I can feel significantly "cooler" (It's still warm, but not HOT).

I thought I had some pictures available, but I don't have them on this comp. I'll try to come back and show you what I'm talking about.
I'm thinking about taking on this chore myself. Do you recall what you spent on all that Sam's Club foil? Thanks.
jpham641 year ago
It appears you have placed the foil directly to the under sided of the roof. However, my reading on-line indicate that an air gap is required for a radiant barrier to work. http://www.radiantbarrierguru.com/new-videowhy-is-an-air-gap-required-for-radiant-barrier-to-work/.
Really? In some of the pics, it might look like it, but in the pick where you can see one side with the barrier installed, and the other side not, you can clearly see he's stapled it to the rafters, leaving the air gap he talks about all through the instructable.
geosuz3 years ago
Thx for your article - but I was wondering has anyone thought to connect the vent the cool house crawlspace to the attic?
charlieb0003 years ago
one limit to this is it reflects outsude heat out, but in winter you want inside heat reflected back in. and you need shiny on inside too. so double the foil.
jimknight3 years ago
The radiant barriers shown on the picture are good.it clear the idea how it would be useful to install and comfort with installing radiant barriers.

http://www.kleenairservices.com/
jimknight3 years ago
Nice, you got it less than $250. Can you give me a link or more any informatiom regarding from where u got it?.
Thanks to share this with us. T
hat is the nice idea to know the process and install it with ourself and savings.
adambeazley6 years ago
When i was first researching radiant barriers, I was going to use the store bought aluminum foil, but found that its just easier, cheaper and better to just buy a heavy duty double sided radiant barrier from a good company.

I got 2,000 sq ft for less than $250 and did the installation myself. I definitely notice the savings and the attic is much cooler in the hot summers down here (Louisiana). Here is the stuff I used: Raflect Radiant Barrier
Cheaper? take a peak @ BlaineC's post higher up. Apparently he covered the same ground with less than 1/5th the cost. Although it is true that he might not get as good of insulation as the commercial product but you cant say he paid more to get the job done.
LVGene4 years ago
..sigh..

Well if you were going to use Foil..  Might I suggest you go to a commercial / (Near Commercial) food store.  The kind of store that sells to Restaurants. 

Special Costco's, Smart & Final, are the stores I'd use here in Las Vegas.

They sell heavy duty and very WIDE foil.  I wouldn't even attempt this kind of DIY without heavy duty foil.

Hope this helps.

GENE
RadiantFoil4 years ago
Radiant barrier works well in both warm and cold climates.

During cold winter months, up to 75% of your home or building's heat can be lost through your attic area.  You may already have fiberglass or cellulose insulation in your attic but these types of insulation only RESIST heat transfer.  Radiant barrier REFLECTS up to 97% of radiant heat back toward the living space, keeping your home warmer and saving you on energy costs

Radiant barrier installed under the roof rafters in your attic can reflect up to 97% of the sun's radiant heat waves away from your attic keeping your home cool in the warm summer months.

More information: EcoFoil Radiant Barrier 
SpudMaker4 years ago
FYI, here is a good video of installing radiant barrier attic foil.


Why make radiant barrier when you can purchase a much better product for the same cost of these items. Not to mention that kitchen foil isn't nearly as effective as the real thing. It is not pure aluminum. Just buy a roll of ARMA FOIL or some other brand. It will be much stronger and will perform much better.
http://www.energyefficientsolutions.comHere is another good radiant barrier site showing several different locations and methods of installation.

lego4115 years ago
oh, and you could get a two-for-one if you use this in conjunction with tesla's radiant energy collection thingy. ... and hey, if you coat your entire attic, you have yourself a faraday cage too! three birds with one tin foil... er.. multiple tin foil... aluminum actually...
This site has a lot of good radiant barrier information and you can buy online too:

http://www.radiantguard.com
tacamaral5 years ago
I believe you could also paint the roof white - that would reflect a lot of heat, as well. I might be wrong on this one, but would painting the underside of the roof black help in any way?
SpudMaker6 years ago
I needed 4000 ft for my home. I purchased heavyweight double sided Radiant Barrier Attic Foil from AtticFoil.com Check out their install method for high pitched roofs.
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ouch you have space to move around in lol
BlaineC5 years ago
Living in south Louisiana, we have very very hot and humid summers. But I am cheap. So I inquired with the Dept. of Energy web site about the wisdom or foolishness of using store-bought Reynolds Wrap foil instead of the Home Depot style radiant barrier roll. The only difference is in how easy or difficult it is to handle the foil. The paper backing and fiber reinforcement gives the Home Depot product more strength so it doesn't tear as easily, but this does not have to be air-tight. So I went to Sam's Club and bought three 500 ft. rolls of the restaurant-grade heavy duty foil. Turns out my 2300 sq. ft. house only needed about 2 rolls at $20 a roll - $40 - not bad. It did tear occasionally but it was manageable. I suspended the roll using a short piece of pipe hung with two pieces of rope nailed to the rafters on one end of the attic and just walked it across the whole length of the attic to the other end, then stapled it up, then did the next row. I had a wide open simple square attic so this was much easier than if there were lots of intricate spaces, but I don't think the paper-backed product would have been significantly easier. I left about a foot from the eaves and the roof ridge so air could enter and leave. Unfortunately, my a/c unit died a few months later and I replaced it with a much more efficient unit so I have no before-and-after measurements to know how well it worked. I eventually installed a powered attic ventilator fan which was the strong recommendation of my A/c man - about $100. This makes a big difference as well, although it consumes electricity (unless you buy the solar-powered version for more money).
jeff-o6 years ago
This is a great idea. I did a bit more research, and found this site:

http://www.ornl.gov/sci/roofs+walls/radiant/index.html

It provides some great background information on how the radiant barrier works, where it can be installed, and some extra info on using it in really cold climates. I'm planning to renovate my attic in the next year or two, and will definitely consider adding a radiant barrier in addition to traditional insulation.