Radiant Barrier Foil Insulation - Why Is Air Gap or Space Required?
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- เผยแพร่เมื่อ 14 ต.ค. 2024
- Ed Fritz, the owner of AtticFoil.com illustrates why you MUST have an air gap on at least one side of the radiant barrier foil insulation for it to be effective. In fact, without an air gap, heat flow is actually accelerated through conduction or conductive heat flow.
Ed also explains and demonstrates the difference between reflectivity and emissivity and he explains why you can never sandwich radiant barrier between two objects and still have it work.
This video gives tips on adding radiant barrier to walls and why you cannot put radiant barrier directly between the shingles and your roofing felt or deck when you re-roof with new shingles. Radiant Barrier Decking works off of emissivity rather than reflectivity. Learn more about reflectivity and emissivity on our website: atticfoil.com/...
Visit www.AtticFoil.com for complete information on Do-It-Yourself Radiant Barrier installations, tips and tricks and order online 24 hrs/day with FREE SHIPPING!
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Usually one layer is all you need. Putting AtticFoil on both the bottom of the roof rafters AND on top of the insulation will have a some additional benefit.
When you consider the extra time, money and effort for the second layer it is usually hard to justify doing both. I have had some customers do both with great results. I would only consider doing both in a mixed hot & cold climate area. Visit AtticFoil(dot)com and look at the "Best Install Method" page for more info.
great video and explains the need for an air gap. Thanks. We added radient barrier many years ago to out attic rafters and it helped a lot.
Thank you for being honest on how this works!
I'm replacing some old insulation in an exterior wall but only have 2 inch gap to work with so I'm using double foil rigid insulation. Glad i watched this video as i realize now how important the air gap is .
You would be better off with foam board and www.AtticFoil.com or look at our www.BlueTexInsulation.com products. The bubble foil products use Mylar and will eventually fall apart.
I learned so much. Glad I watched this before insulating my vehicle. Thank you.
I wish I had watched this before I insulated my garage door. LOL 🤦♀️
Nice easy to understand science, thank you for your knowledge.
Great explanation about radiant heat.Thanks.
I saw a few videos mentioning the air gap that is a part of radiant heat! Nice explanation
Thank you so much for your explanation.
Thanks!! I love satisfied customers!!
The paint is in direct contact with the bottom of the roof deck. By doing this, the paint or foil backed roof decking is working off the emissivity quality of the aluminum. The required air space is actually the attic space. The foil backed decking works very well and is good option for a new roof deck.
The low emissivity surface from paint or foil causes most of the radiant heat to be lost upward from the roof rather than into the attic space.
Nice video and explained very well and clear. Thanks for sharing.
Thank you for saving me 5 minutes before I was about to do what nor to do
Yes, generally galvanized staples are used. There could be some reaction between the steel and aluminum, but the contact area is so small this is not a big concern. I've got thousands of customers and never heard that it was an issue. You could use plastic staples if this is a big deal.
I see roofers installing this directly under shingles. FYI it’s just going get hotter and bake the shingle more. They have no idea how this works. Thanks guys
I heard of some lawyers who have got their clients free roofs with just a letter when thew sold a "radiant barrier" directly under the shingles. Does not work that way.
thank you! Your informative videos are great.
Excellent explanation - the best I've come across
Thanks!
This was very educational, thanks!
We have this in the walls, built back in the 70ts. mostly replaced with thicker walls and insulation but it acually worked decent. Maybe its something to think about - using foil And insulation!
Yes, here is the way to www.AtticFoil.com in an exterior wall: atticfoil.com/index.php/applications/inside-exterior-walls-hotmixed-climates/
Very good explanation... thanks
very informative and helpful thank you,
Excellent video
fantastic video, thanks for making this!
Well done. Thank you.
Learned a lot, thank you.
Taking your example with the air gap between the skillet and the foil: would the foil still work to reflect radiant heat if it was partially obscured by, say, a gauzy fabric? Or does it need to be 100% clear to radiate the heat?
My application is for camper van window covers, and whether I can get away with putting a thin cover of fabric over the foil, or whether that would negate its benefits.
If you maintain an airspace between the fabric and the foil, it will still have the full reflectivity value.
What do you think of this new roofing material with the radiant barrier already attached to the inside part of the roof? Also, if your home has this would it still be a good idea to add your attic foil... By the way, I enjoy the videos and information you provide.
Ok I was wondering about it touching insulation. So basically half inch free space. Does the air bubbles wrap plastic not count as air gap space
Yes, 1/4" or more is all you need. www.AtticFoil.com does NOT have air bubbles. And, you should never use a bubble product in an attic. No, the bubbles do not count as an airspace because there is a layer of plastic that makes the bubble between the bubble (air) and the foil. So, technically, there is not an airspace next to the foil.
now I understand thanks
great, thank you!
Is there much point in using multiple reflective layers, each with a gap? Or is the first one reflecting most of the heat?
Not much of an additional benefit for more layers. Like having two umbrellas.
Thank you for the very good explanation. I have a question that you might be able to answer. I’ve seen some garage door insulation videos using a radiant barrier mounted on foam. The one I am thinking about using is one with a thin foam radiant barrier that uses spacers between the garage door and the barrier to create the air gap. Will this work effectively in your opinion?
My method is easier and better in this video: th-cam.com/video/OROTrjn1j9E/w-d-xo.html
Is this the same with cold? Like for example, if I have a van with aluminum floors and put cork insulation directly on the floor vs creating a 1/4" to 1/2" air gap between a layer of foil and then the cork insulation. I mean will that airgap keep more cold out???
Technically, you don't keep the cold out, you are trying to keep the heat in. In your case most of the heat lose through the floor is by conductive heat flow, not radiant heat. So, the cork is actually better. The www.AtticFoil.com would be best for the roof/walls that catch sun and you are trying to reduce heat gain when the sun is out.
Great explanation. I live in New England and am considering putting this up in my attic as well as in a couple of crawl spaces in my basement attached to the rafters. I basically want to trap heat in the attic and above the basement. My attic is about as high as the one in this demo. How much heat do you think I could realistically reflect back if the areas are cold to begin with. Attic is a little warmer than outside temp. Thanks
Probably not much... because most of the heat in your attic is not radiant heat, it is from the warm air rising through your home. That heat is a convective heat. Better off sealing the roof well from air leaks, and installing insulation if you want to keep your attic warm.. But need to be careful!, the roof should remain cool to prevent ice buildup on the outside... this is prevented with air baffles (hopefully you figured that out after 13 years haha, cheers)
If this is the case then why do you recommend rolling your Bluetrx insulation out around the frame of a steel carport/metal building and then putting the outside metal panel ageist it and causing it to be sandwiched between the tube post and the sheeting
We never say this. If you look at this page there are multiple places that mention (with pictures) using hat channels, wood or foam strips to create the required airspace in order to have a radiant barrier. bluetexinsulation.com/pages/new-construction-metal-framed-buildings-installation
So gor a house in winter heated by hot water radiators (which fo not radiate, they convect!) How effective is a reflective foil?
A radiant barrier like www.AtticFoil.com is definitely more effective when a radiant heat source is used compared to a forced air system. Basically, there is more "heat" to reflect/keep in.
is there a minimum air gap size for it to work...10mm, 20mm..?
Do this foils have a direction side or doesn't it matter what side is be used 🤔
Both sides are the same. atticfoil.com/index.php/products/48-wide-double-sided-atticfoil-radiant-barrier-foil-perforated/
On hot summer days would it be useful to put some type up of radiant barrier over inside windows?
If a window is in direct sun, YES foil works great to reflect heat. Does is look Ok??? That's your choice. www.AtticFoil.com
@bumhokim There is a new testing procedure for flame and smoke. This is called the ASTM E 84 and ASTM E 2599. Nothing changes with the product except it must undergo a different method of testing. Eventually codes like the IRC, IBC, and IECC usually adopt the ASTM Tests. It will be a while before anything happens. Right now nothing has changed.
I like the radiant barrier decking since you get good results for a low cost and no additional labor. But, it can only be done if you are installing a new deck. As for adding AtticFoil BELOW radiant barrier decking? If you are willing to do it the results are AMAZING! You can stand below the two layers of foil with decent attic ventilation and not even know the sun is out.
At seventy two and living in a stressful world my understanding is not all there, i have a very cold basement and i was going to put some of the foil on my wall.so do i have to have a gap? i also was going to put on two layers.can i do that? thanks for your reply.
For a basement wall, I'd look at our products at www.BlueTexInsulation.com Honestly, you don't have a lot of radiant heat coming through those walls.
So if i have rgid foam insulation that has a radiant barrier on one side and I want to install it between the studs on an interior shed wall, is that doable if i leave an air gap between the radiant barrier and exterior wall?
Yes, you are basically doing this AtticFoil wall method: atticfoil.com/index.php/applications/inside-exterior-walls-hotmixed-climates/
@ChrisUTMBA Bubble foil is a decent product. However, it usually works no better than AtticFoil - It's the foil doing all the work to reflect radiant heat. The only airspace is on the outside of the foil since it cannot have an airspace on the side that it is glued to something.
@ak99372 Bubble foil around ductwork is a lot of work for very small benefit. You must be very careful to maintain an airtight airspace. You are better off using a standard radiant barrier/fiberglass insulation duct wrap. you will get more, r-value, it's cheaper and it's much easier to install.
I'm stud framing a shipping container and will cover it up with 1/2 inch sheetrock. Can I install radiant foil as the only means for insulation between the sheetrock and the steel?
Check out our new Foil/Foam products at www.BlueTexInsulatioin.com
So the foil is for summer insulation or better to reflect heat?
It is not used for maintaining the heat in the house during winter?
It actually does both. However, it is most effective at reducing Summer heat gain.
I have a question. In order to insulation a garage door in California climate, do I need to put reflective foil facing garage door with some air gap, or facing the inside the garage? Do you have any material for garage door insulation? Thanks for the info.
You want the airspace facing the hot door. Here is a method/video I did. th-cam.com/video/OROTrjn1j9E/w-d-xo.html
Can I put insulation reflective sheets on top of existing roll roof?
Then add 1x4, and metal on top
Yes, we have a special product for that that many roofing contractors use: www.roofingfoil.com/shop/single-sided-solid-foil-underlayment/
That would be the perfect emergency blanket 🤔 97% heat reflection not bad 😊
Thank you
I've seen plenty of camper-van conversion videos using this product to insulate, or using it as a vapour barrier, now if I'm to use this on my camper-van ceiling due to the limited space will I achieve any R values if I install this leaving a 1/2 inch air gap from the bear metal of the van ceiling as I want to avoid the van getting hot in the summer but also have warmth in the colder climates, i'm unsure due to it being metal if I also need another form of insulation, any advice would be much appreciated? thank you.
The typical install method for van/bus conversions is Metal>Airspace (Usually made up of furring strips) Foil. Check out our new product that is perfect for this application. bluetexinsulation.com/products/bluetex-supreme-foil-white-6mm-foam-radiant-barrier It's basically metal building insulation, but we have been selling a lot for these type of applications.
Can this foil be used in outdoor saunas? what is the maximum temperature it can be exposed to?
Yes, it can be used in saunas. In fact, we have a customer who puts them in all the saunas they build and have used it for years. Max temperature over 200º F.
Thanks for this and saving me money on this useless product I was going to use it in a campervan conversion but its practically useless for wall insulation.
If i cover cool bottled water with radiant barrrier with it remain cooler for longer under sunlight ??
Yes, it would almost be like putting the bottle in the shade.
Hi, does the air gap have to be on both sides of the barrier? or just one? I want to fit plasterboard onto the rafters but also use a radiant barrier. Thanks
Just one side. Depending on where the airspace is will determine if the www.AtticFoil.com works off of the reflectivity or emissivity quality of the aluminum foil.
Does the air gap have to have moving air?
Not required, but best to have a ventilated airspace. Ideally we "back ventilate" any exterior cladding. But if you can't, you still get the benefit of the radiant barrier but not the "cooling" effect of air moving across it.
I'm looking at insulating a shipping container. So do I put the reflective backing down first, then the insulation, or is it the other way around? And if it's the reflective first, can I place it directly onto the metal, or do I have to create a gap?
You will need airspace between metal and foil.
Hi, So I'm looking to insulate a van...Would it work to attach SilveRBoard or AtticFoil, not directly onto the van walls, but onto the raised interior parts of the walls and roof, essentially creating an air gap between the van wall and the radiant barrier? Thank you!
Yes, it would work great. We have many customer convert shipping containers into usable space doing this same method.
What about corrugated iron roofing which has over an inch of air space between the corrugations? Can radiant barrier be installed with no gap?
Because of the corrugations, you DO have the gaps. It depends on how much of the roof profile touches the deck. The more direct contact, the less benefit. Take a look at this video show the "direct to deck method" th-cam.com/video/_lPdS3wwtLo/w-d-xo.htmlm41s
Trapping heat and trapping air are two different things. You cant use the attic temp as a gauge. Ideally, you want you attic cold and dry. Radiant heat will still be reflected back by the foil. Your "Thermal Envelope" should be an airtight box, that is well insulated to reduce air infiltration and conductive heat loss. Then, wrap that "box" with foil to reduce radiant heat loss/gain.
Will insulation foam under corrugated sheets work?
Work to do what?
If I put this inside on corrugated iron ceiling, will the grooves from the corrugated iron act as the gap needed? Or not. Thanks.
Yes, the grooves will be enough to provide minimal surface contact.
@@AtticFoil Thanks for getting back to me.
@@AtticFoil Its up!! I'm so pleased I discovered this product because I can tell the difference straight away. Its for my cortijo in the mountains in Spain :)
Can I put Attic foil over baffles instead of foam board like in your video? Cathedral ceiling to be insulated.
Shane Waller Not sure by what exactly you me by "over". If you mean below the roof deck and then styrofoam baffles, this may or may not work. It really depends on how much of the foil is "sandwiched" between the baffles and the insulation. The foil MUST have an airspace on one side to work. Can you replay and describe the "layers" you propose coming from the roof down including all air spaces?
Adding attic foil would it shortened the shingle life span?
The roof temperature over a radiant barrier usually only increasers about 5-10 degrees. This is generally considered to have a very minimal effect to the life span of the shingles. Here is a video with thermal imaging showing the difference in roof temperature on a roof with part done with AtticFoil and part done without. th-cam.com/video/OHpyv_kxmoI/w-d-xo.html
can i put insulation under my wooden floor up against the wood , would i put foil against wood or away side , or does it come with foil on both sides
It sounds like you are doing a crawl space application. Here is the info you need: atticfoil.com/index.php/applications/crawlspaces/
@@AtticFoil thanks
I have a flat shingle roof, with metal roof over, stabled by footers, to create small pitch. There's a big space between the 2, like 6". Can I install Radiant Barrier product directly to my shingles? The dead Air Space is there.??
thewildlifecrew Yes, if you can get the radiant barrier between the metal and the shingles this will definitely help. If it's ventilated air, it will perform a little better then if it's dead air. The airflow will help cool the metal roof, reducing the initial amount of radiant heat produced.
Hello..i would like to install roof insulation on our 2nd flr ceiling but my problem is ceiling already installed..how would i put insulation? Thanks
You would need to get into the attic somehow.
A little late for the party, but I was hoping someone might be able to help; I'm looking at insulating RVs in a more modern fashion and have been trying to play with Radiant Barriers. One thing I am trying to overcome is the air gap, or "attic space". RV ceilings offer little room to work with, but does anyone think that a layer of large cell (expanded) polyurethane could play the part? Enough air in between the cells to act like an air gap? Thanks in advance.
Not really. It can be a real challenge to get the required airspace in many assemblies.
Yes Keys, use closed cell polyurethane foam immediately under/behind the vehicle skin. Air gap is only used in primitive buildings to insulate from outside.
AtticFoil Radiant Barrier Foil Insulation
If I was to install this insulation in the van and leave a suit gap between the outer panel by stretching/fixing the foil insulation across the inner "spines" (supports) of the van.. Would this create the air gap you talk of?
Also does doubling up on thickness = doubling up on "r" value?
Yes, on the airspace. No on doubling up. Foil is like an umbrella, it has no r-value.
Only means of insulation? It really depends on what you are trying to achieve and what your climate conditions are.
Would heat increase in gap ( void space ) damaging electrical wiring?
It should not cause any damage to wiring. The increase in temperature (surface temps) inside the gap would probably be less than 10-20 degrees. The top roof surface temperature usually only increases less than 10 degrees. This increase should not be significant enough to cause any damage.
How far do you need the air gap for it to work?
1/2" or more is ideal - But once you get past about 3/4" there is no additional benefit. If the airspace is "vented" then even a 1/8" or 1/4" will work. If the airspace is "dead" then you want to have at least 1/4".
I have a steel roll up door I wanted to put a barrier on the inside held down by magnets(there's a yt video). based on your video it wont work bc there's no air gap, I am I correct?
No it will work. The inside of the garage IS the airspace. If it's directly up against the metal it will work off the emissivity quality. You just can't "sandwich" the foil and have no airspace on either side. This video may explain it better: th-cam.com/video/uGP5KobU6R4/w-d-xo.html
My question is; Do NOT buy a closed cell foam board that has foil on both sides, as the "sandwich" will NOT work as an insulator? I just watched a competing video which is using 4 inch solid foam with foam on both sides. It stated it will keep the heat out in the summer due to the foil on the outside and the interior heat "in" during the winter due to the inside foil. This was mounted in the attic against the roof rafters. HELP!
+Randy Lavine I have seen this product and technique. What they are proposing is to MOVE the thermal boundry to the bottom of the roof rafters and "SEAL" up the attic space below. I have NO problem with this method and it works very well. I basically did the same thing on my house: www.radiantbarrierguru.com/combining-radiant-barrier-with-spray-foam-insulation/ It it pretty costly, but it is very similar to going to a full foam encapsulated attic (which I LOVE for new construction) My only conceren with the 4" foam with foil on both sides is that it can almost work TOO well. What I mean is that it can reduce the heat load SO much that it can now cause the air conditioner to be WAY OVERSIZED. The result is that the AC will not run long enoug (short cycle) to remove the latent heat. (moisture) It will easily remove the sensible heat, but without running longer it may not "condition" the air by removing enough moisture. IF you combined the 4" foam/foil/sealed attic with an inverter AC system that will run at part-load, then it's a great system.
Thank you! What does a roll of your product cost? Here in Las Vegas (where we are currently looking for a fixer home)I think it will pay off in one year!
+Randy Lavine +Randy Lavine This is our most popular product - 48" wide www.atticfoil.com/products/48-standard.html We also have it in 26" and 60". Cost is about $130 per 1000 sq. ft. With shipping you would be at about 15 cents per sq/ft.
+AtticFoil Radiant Barrier Foil Insulation .15 sf for something that reflects 90+ % of the heat that literally beats down and pounds the hell out of a building, the a/c system, and ultimately our bodies . . . now there is a bargain!
Hi Ed, I'm trying to stop heat from going from the radiant heat in my kitchen floor into my basement. My basement is getting warm but my kitchen isn't. Any recommendations?
Check out my pages on radiant heat over conditioned and non-conditioned spaces. www.atticfoil.com/index.php/applications/radiant-heat-flooring-over-non-conditioned-spaces/ If you can access the pex tubing, this is an easy and effective way to direct the heat upwards towards the kitchen. Please send me some pics if you do this. We don't have much radiant heat in Texas. (or basements)
I can't access the radiant tubing... that's a catch. i'll try and find some pics. thank you for the reply !
Picture link did not work. Please go to the Contact Us page at www.AtticFoil.com and you can submit there. Thanks.
i'm building a 40'x60' shed myself with 2'x6'x12' exterior framed walls on 16" centers. I'm installing rockwool insulation in the wall cavities and planning to use 2x4's horizontally across the studs to provide that "air gap" before installing the reflective radiant barrier. Then osb finish on the shed interior walls. This gets my walls flush with the 8" foundation concrete walls at the bottom that are raised about 12"-18". Does this sound acceptable for the given application?
Sounds like a great application. You basically are doing a house wrap application like here except with metal: atticfoil.com/index.php/applications/house-wrap-behind-brickstone/
In other words what we learned in 7th grade physical science class. Remember why polished silver tea sets were popular?
If you managed to install your radiant barrier half an inch under your roof, and if you got 100 units of heat from the sun, and your radiant barrier reflects 97 units back, doesn't that 197 units total fry your roof?
Short answer is no. Roof temp only goes up a few degrees. Full info and video here: atticfoil.com/index.php/knowledge-zone/knowledge-zone-learn-about-radiant-barrier/myth-or-truth-radiant-barrier-damages-roof-shingles/
@ak99372 Bubble foil has an R-Value of about 1 since it's only about 1/4" thick. Any additional r-value you see advertised is in the form of a "dead air space" which is very tricky to achieve on ducts. It's not worth even trying. I'd keep it simple and buy some "duct wrap" - R-4 to R-8 with foil on the outside. It's a standard issue product in the HVAC industry. Before insulating you want to SEAL the ducts with a good quality mastic. Seal then insulate. Need more info? - AtticFoil-dot-com
How much air gap would be enough ?
1/2" or more is ideal.
@@AtticFoil thank you
Embarrassing question: Can I use Heavy Duty Tin Foil as my Radiant Heat barrier? I can't afford the real product.
thewildlifecrew You could use regular foil for a staple up method, but not over the insulation since it is "solid" and is a vapor barrier. However, regular foil won't hold up long. Just the weight of the foil and a little breeze through the attic will rip it off, or any critter in the attic will pull it down.