DIY Attic Radiant Barrier

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Introduction: 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

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

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.

Step 4: Conclusion

I have not done any baseline and/or final testing, like a good engineer would, but I do that at work. I know this will work because of the great reflective properties of aluminum with an air gap. The air gap is the real reason for attaching to the rafters. There are two other ways to add an after construction radiant barrier, spray on and attic floor. Those two methods are not as good as the rafter method because spray on has no air gap and the attic floor barrier collects dust. The best barrier is the roof designed with reflectiveness built in, but most people don't think of that or want the cost associated with it. By the way a radiant barrier may not be well suited for your climate, I would perform research before committing the time and energy to installing one. Well this ends my first Instructable and hope it was useful.

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    39 Discussions

    0
    aking14
    aking14

    4 months ago

    I'm doing this currently in 2019, so here's the info for how it's working out. I was already getting ready to blow in extra insulation for the winter and insulate the garage, then ran into this so doing it now quickly before I double the insulation depth and make it more difficult.
    Per 68caliberkiller 's post I like the idea of just stapling the foil directly across the rafters, 18" wide x 75' long box of HD Reynold's Wrap foil is $5 ish vs $10 for the 12" x 130 feet. Close to the same and 18" wide so it'll go a bit faster. For backing there was Lowe's Item # 125855 Contractor's paper. It says Currently Unavailable on the web but they had it, but not Blue Hawk it's Trimaco like some of their other papers. In the same area as the other paint masking papers, but this was much thicker so look around that area. It's 28" by 140 feet for $10, so it can go vertically behind the foil going horizontally. Also get a cheap hardhat, Lowe's is closing out some right now for $4, well worth it to not be banging your head on rafters.
    I'm thinking to staple the foil up just as he did, and then staple the backing behind it, no glue so no cost. Could create an extra air space and condensation, but I'll keep an eye on it and take measures if necessary. Going to do it in the next day or two so I may report back on how it goes.
    I'm putting in durovent eve vents in the new areas for the blown insulation, and adding more for the areas that already have them where I'm increasing the height. Mentioning this because note that you can also use these all the way up to the ridge vent, to create a hot air channel for similar savings but doesn't have the radiant barrier. The foil will do similar without the vents though. But, per code for the vents every 4' vent up the rafters you're supposed to leave a 1" gap. This is probably for some air exchange so you don't get completely trapped air and cycling condensation. Mentioning this because you may want to leave a gap every 2 or 3 18" rolls of foil up, so you're closer to code and don't trap the air behind the roof sheathing too much. Google image search roof sheathing rotting to understand what can go wrong. Also a very good idea to check behind this every 6 months or a year the first couple, then every 2 or 3 years at least after that. Really I try to go up at least once every spring and fall, just to check things out when the temperatures are reasonable.
    Anyway just for reference and hope this helps someone. I'll try to post back when I check it next summer. I don't have the before temps logged, but here in the summer sun I'm sure the attic hits 130 to 140 at it's hottest, and it's instant full body sweat as soon as I go up there when I've had to mess with the AC during a summer day. So if this keeps the attic within even 5 or 10 degrees of ambient during the hottest part of full sun days it will be obvious it's working and worth doing.

    0
    ScottL211
    ScottL211

    Question 1 year ago on Introduction

    why didn't you just buy the radiant barrier reflective insulation? it's not expensive. aluminum foil from the grocery store costs money too and is flimsy.

    0
    68caliberkiller
    68caliberkiller

    5 years ago on Step 4

    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!

    CAM00391 (1024x768).jpgCAM00392 (1024x768).jpgCAM00390 (1024x768).jpg
    0
    KimberlyW101
    KimberlyW101

    Reply 2 years ago

    I'm trying to figure out a way to cool a small potion of my attic for storage. Do you have any tips? Also, How did this end up working out for you temperature-wise in the long run?

    Thanks

    0
    TonaM3
    TonaM3

    2 years ago

    This is a true DIY write up. But I would suggest to save some time (and maybe money - anyways, time IS money) and get perforated attic foil.

    Not only is ready to install, but it provides reflective material on BOTH sides, not just one as this write up depicts.

    0
    lucjoker
    lucjoker

    4 years ago

    so much work.

    foil does reflect the sun light , but installed under the roof ,there is not reflexion at all.

    I live in thailand ,tried it all .The foil is metal and just heads up like anything else .

    To keep your living room cool, you will have to insulate the sealing (not the roof )

    Prevent the hot air in the attic to touch the sealing.Ventilate the attic with a big fan or

    The best insulation is"hard "insulation board.The best R-value.

    Heat will penetrate anything, it depend how slow it does it .

    If it takes 12 hours ,than you're ok, by that time the sun will be down .

    The r-value of your insulation will tell you how thick it has to be to withstand

    long enough.Try the cheap stuff first ,

    put a layer of 20 cm, not cool enough?...add annother 20 cm.

    Still not cool enough , build a new house and do proper insulation needed for the area you live.

    0
    TonaM3
    TonaM3

    Reply 2 years ago

    You still need ventilation (addresses convection) and insulation (addresses conduction).

    But a radiant barrier is very effective addressing another way to transmit heat: heat radiation. In combination, these are very effective means to keep your attic (and home) cool.

    So this works, but you also need to address other ways that heat gets propagated.

    Another fix is simply adding foil to the other sides but it wont be effective reflecting existing heat back in during the winter unless you have a space between the foil and the roof sheathing.

    the foil cannot radiate heat but is a excellent conductor of heat. Since the foil is touching the paper it is conducting heat into the paper and then the paper radiates it into the attic. If you face the foil in the attic and the paper out toward the roof it will work much better. A rule of thumb is to make sure the foil isn't touching anything on the side you are insulating. You can test this by turning one piece around and after it heats up in the attic, hold your hand beside the foil and it should feel cooler than the others. if you touch it the heat will transfer into your hand and burn. the heat is blocked until another conductor touches it (as in the paper).

    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.

    0
    rcg40
    rcg40

    8 years ago on Introduction

    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

    1
    kkuepker
    kkuepker

    Reply 5 years ago on Introduction

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

    1
    rcg40
    rcg40

    Reply 5 years ago on Introduction

    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.

    0
    tradergordo
    tradergordo

    11 years ago on Introduction

    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...

    0
    crowdjs
    crowdjs

    Reply 11 years ago on Introduction

    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.

    0
    tradergordo
    tradergordo

    Reply 11 years ago on Introduction

    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.

    0
    alexlutor
    alexlutor

    Reply 7 years ago on Introduction

    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.

    0
    Lyteswitch
    Lyteswitch

    Reply 5 years ago on Introduction

    I'm thinking about taking on this chore myself. Do you recall what you spent on all that Sam's Club foil? Thanks.

    0
    jpham64
    jpham64

    6 years ago on Step 4

    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/.