The property that aluminum has going for it is its emissivity coefficient, a measure of how much infrared it radiates compared to a perfect "black body" which has a coefficient of 1. Aluminum foil typically has a coefficient of 0.04. Wood is typically 0.9 or higher, so aluminum foil will radiate about 20 times less infrared than wood if they're both at the same temperature.
I wish more builders would get on that soap-box with you. That was the best explanation of radiation, convection and conduction I have ever heard! thanks.
Thanks for this video. What I did was do both. I just had my roof done and silver side up. I also had radiant barrier SPAYED done in my attic (giving me a 50-60 degree difference) and had 7-10 inches of insulation added, attic tent and I have two a/c units for each side of my 2500 sq. ft house. Sealed all my can lights, changed all light bulbs to LED's. My utilities went from $400 to $100. My thermostats are on 78 and 82. I also used purple insulation on the garage door. Whoo Hoo.
Your analysis of convection and conduction is correct, radiant is not. Heat does not travel by radiation, heat is the conversion of radiation into thermal energy. Flip your foil around and add an air gap between the shingles and radaint barrier, it will work much better. Just like they do with satellites in space... foil needs to face radiation source.
It's a great comparison, I would have liked to see the temperature difference inside the cabins as well. And I'd like to see if there would be a difference if you added venting in soffits and has a tower vent. Great stuff.
Make a third doghouse and put the aluminum facing up. Tape the joints and nails. Put 2x4 furring on that. Deck it again then roof it. Check the difference between it and the others.
thank you so much for clearly explaining how the 3 methods affect us and how Radiant barriers work. It's so great to see you putting out content again!!!
what happens if you add an air gap between the shingle and the aluminum (faced up)? does the air gap change anything because now the shingle is not conducting heat?
Great lab assessment, could you now build the dog house with spray foam and with a dual frame ? could you also get a third temperature of the local weather measurement
Roof vent + air gap + radiant barrier = Win. I don't think I would use LP TehShield RB. Maybe they can make a product with an integrated air gap so the warm air can move out with natural convection.
Does anyone build a roof like that? Do you even need a radiant barrier if you are willing to build what equates to the cost and materials of two roofs?
Very interesting video. Does the same apply if you have a steel roof instead of asphalt? In the vanlife community (those that live full or part time in vehicles such as a Sprinter van), there is a lot of misinformation on how best to install the radiant barrier. We've done this - steel roof, air gap of 2cm, then reflectix radiant barrier, then 2cm air gap followed by insulation followed by wood panels for our ceiling. Is this the way to do it?
The last time you had a video about this, someone I follow on IG was putting a similar product to this right over existing roof sheathing. After letting him know that without an air gap it wouldn't do anything, he talked to his roofers who must have researched it a bit more, and they agreed. They then charged him the same price as a premium osb roof decking of the same thickness. Btw, did that shed get an addition?
I'm guessing that this is more popular in area without cold winters. I don't see it at all around Ontario, Canada. Just well vented attics to protect asphalt shingles from getting hot enough to cause degradation in the summer and ice damning near the eaves in the winters. Then a big layer of insulation between the attic and the living area.
Hey Jordan, what if im building a warm roof and I have the shiny side facing the air gap which is "out." Is it worth it? Thanks so much man. Love your videos
My builder installed the OSB with the foil side toward the attic. Plus, he installed Galv-alum standing seam steel roofing. I'm not sure that's better or worse than what the folks selling the foil radiant barrier and telling us to install it on the bottom of the rafters or trusses to leave the air gap between the roof deck snd the radiant barrier. Your opinion?
In my attic I have to install shiny side pointing into the attic. Reason? The HUGE amount of heat in the attic that I need to reflect away from the living space. So far it has kept the livable space a decent and constant temperature with no wild swings in heat. What about that foam insulation that is shiny on both sides?
I don’t think there are more than 3 videos. I might get a bucket of that paint and spray it on my unfinished garage rafters/sheathing to see if it actually keeps heat in, (In Utah, gets below freezing at night) and in the day mid summer, gets over 125 in the garage, place is a sauna).. looking to just keep heat in at this point, now if I can just find me some of that paint, and if I can spray it with airless sprayer..
Great example of how it works. In Australia foil barrier is sometimes 'draped' under the roof in thin flexible 'film' sheets. This is usually a retro fit. I wonder how much better that would be with 2 air gaps? The surface facing up could become dusty over time. Does that dust effect the emissivity on the upper surface?
I think it actually pulls double duty when hung like that. The air gap on top lets it reflect heat (basically its reflectivity is as high as its emissivity is low). Even if the top gets dusty and it absorbs more heat, as long as the bottom is shiny, it still won't emit much downward. This is just kind of speculation based on physics fundamentals - I basically never hear anyone talking about both features at once. Makes sense to me, though.
I find this counterintuitive, but I don't doubt it is true. I think LP TechShield is mostly for warmer climates. Don't forget to vacuum the aluminum side from time to time as dust reduces the effectiveness. I wonder if money would be better spent getting more reflective roofing. It's odd that my cars "radiator" is made out of aluminum. I guess "convector" was taken.
@@FullSendPrecision My understanding of the video is that the aluminum attached to the OSB stops or reduces radiation. Seems weird. I think car radiators work primarily through convection.
@@FullSendPrecision I have fond memories of cast iron radiators. I had a favorite chair near one and it kept me toasty warm as opposed to the leaky single pane windows and barely insulated walls.. It didn't dry out the air like forced air systems.
Thanks for the video Jordan. Could you do this with other roof designs, e.g. insulation between the trusses that would be touching the aluminum, or a flat roof with insulation above the OSB, or how about siding with a rain vent behind it so there's less conduction but want to prevent radiation from the siding/roof to the OSB. What if you're in a colder climate and have to keep heat in. Would you install the radiant barrier in the same way in all of these cases?
Usimg electric air ventilation as heat exhauster on you roof will do the same for quite cheap like factories have on their roof... to release hot air trapped...
I'm going to be building my house with ICF walls in southern AZ. For the roof I want to do closed cell spray foam in addition to radiant barrier on a metal roof. What is the best way to install it? Is that considered overkill?
Silver side is supposed to go up, but you have to leave an air gap. I suspect that you got a lower temp on it installed silver side down because you put a less conductive material against the hot roof, but had you left an air gap, you would have gotten an even lower temp with the silver side up blocking the radiant heat gain. It needs the air gap to prevent heating by conduction (like an aluminum frying pan on a hot plate).
although that is the optimal installation method for a radiant barrier, i don't believe that is the intended use of this particular product. it seems to be a middle ground, in the event an attic space is finished out for occupation
I don’t know, but I doubt it. The radiant properties of the material go away as soon as it contacts the shingles. My best guess is that the aluminum will turn into a high-efficiency conductor, pulling the heat away from the shingles into the OSB below. So best guess- it will just be inert?
If there's no air gap on home 1, the radiant energy cannot disperse, and perhaps it is heating up the shingles even more, causing the difference in temperature...the radiant barrier ahould be reflecting the radiant energy...not sure what its purpose would be in home 2...other then perhaps to keep radiant energy from escaping.
Staple it to the rafters and let it pull double duty. Top side reflects most heat, bottom side will behave exactly like the down-facing foil here. In theory this should work even better than in the video, because if it's integrated with the board, you don't take advantage of its reflective properties.
hey Jordan, you are actually pretty good at explaining theories. The first few minutes could be done better, if cut to a white board and explain the theories with drawings instead of standing next to the 2 props. Just like how Steve B does it with his big red. and then you can cut back to the 2 props to prove your theories. Great to see new videos from you. cheers
This is very wrong. Techshield literally has the words printed on it “must be installed with an air gap” it’s not meant to be glued to the underside of OSB. HEB you lift up your second dog house, it says it right there!
Even the 'correct' one is incorrectly installed without an air gap.
this is great. now build one without any radiant barrier whatsoever and one with an air gapped radiant barrier
The property that aluminum has going for it is its emissivity coefficient, a measure of how much infrared it radiates compared to a perfect "black body" which has a coefficient of 1. Aluminum foil typically has a coefficient of 0.04. Wood is typically 0.9 or higher, so aluminum foil will radiate about 20 times less infrared than wood if they're both at the same temperature.
Great explanation!
I wish more builders would get on that soap-box with you. That was the best explanation of radiation, convection and conduction I have ever heard! thanks.
Thanks for this video. What I did was do both. I just had my roof done and silver side up. I also had radiant barrier SPAYED done in my attic (giving me a 50-60 degree difference) and had 7-10 inches of insulation added, attic tent and I have two a/c units for each side of my 2500 sq. ft house. Sealed all my can lights, changed all light bulbs to LED's. My utilities went from $400 to $100. My thermostats are on 78 and 82. I also used purple insulation on the garage door. Whoo Hoo.
He returns!
Good to see your videos again!
Your analysis of convection and conduction is correct, radiant is not. Heat does not travel by radiation, heat is the conversion of radiation into thermal energy.
Flip your foil around and add an air gap between the shingles and radaint barrier, it will work much better. Just like they do with satellites in space... foil needs to face radiation source.
Easy way to remember it, is it needs an air gap to be able to work. Foil faces the air gap. I think min of 1 or 2" required.
It's a great comparison, I would have liked to see the temperature difference inside the cabins as well. And I'd like to see if there would be a difference if you added venting in soffits and has a tower vent. Great stuff.
Great Explanation. I've been using radiant barrier and foam in all my new builds families are HAPPY this helps reduce Electric Bill here inTEXAS!
Make a third doghouse and put the aluminum facing up. Tape the joints and nails. Put 2x4 furring on that. Deck it again then roof it. Check the difference between it and the others.
thank you so much for clearly explaining how the 3 methods affect us and how Radiant barriers work. It's so great to see you putting out content again!!!
what happens if you add an air gap between the shingle and the aluminum (faced up)? does the air gap change anything because now the shingle is not conducting heat?
I put this on a shed and a modern pergola I built you can feel the difference for sure. Good product.
Thanks Jordan....I wish there was a control dog house for this experiment
Informative, but I think that you need to check your math. 8:50 You're looking at 50 & 70 degrees over the inside target of 70, not 40 & 60.
Great lab assessment, could you now build the dog house with spray foam and with a dual frame ? could you also get a third temperature of the local weather measurement
Roof vent + air gap + radiant barrier = Win. I don't think I would use LP TehShield RB. Maybe they can make a product with an integrated air gap so the warm air can move out with natural convection.
Please do a test to show the difference under the attic insulation. Thanks
That will only show the ambiant air temp though as there is no insulation on the walls and no door
You should have made 3 dog houses. The third one should be made without a radiant barrier.
Does anyone build a roof like that? Do you even need a radiant barrier if you are willing to build what equates to the cost and materials of two roofs?
Very interesting video. Does the same apply if you have a steel roof instead of asphalt?
In the vanlife community (those that live full or part time in vehicles such as a Sprinter van), there is a lot of misinformation on how best to install the radiant barrier.
We've done this - steel roof, air gap of 2cm, then reflectix radiant barrier, then 2cm air gap followed by insulation followed by wood panels for our ceiling.
Is this the way to do it?
The last time you had a video about this, someone I follow on IG was putting a similar product to this right over existing roof sheathing. After letting him know that without an air gap it wouldn't do anything, he talked to his roofers who must have researched it a bit more, and they agreed. They then charged him the same price as a premium osb roof decking of the same thickness.
Btw, did that shed get an addition?
Thanks for that awesome explanation and sample.
Thanks .. allways wounderd . Would aluminum radiate if it was laying on HD styrofoam?
I'm guessing that this is more popular in area without cold winters. I don't see it at all around Ontario, Canada. Just well vented attics to protect asphalt shingles from getting hot enough to cause degradation in the summer and ice damning near the eaves in the winters. Then a big layer of insulation between the attic and the living area.
Hey Jordan, what if im building a warm roof and I have the shiny side facing the air gap which is "out." Is it worth it? Thanks so much man. Love your videos
My builder installed the OSB with the foil side toward the attic. Plus, he installed Galv-alum standing seam steel roofing. I'm not sure that's better or worse than what the folks selling the foil radiant barrier and telling us to install it on the bottom of the rafters or trusses to leave the air gap between the roof deck snd the radiant barrier. Your opinion?
Great video. Thanks very much for the info.
Does this product do anything for keeping heat inside the home during the winter?
any more update in 2024? how about just painting the roof? how much difference will it made?
In my attic I have to install shiny side pointing into the attic. Reason? The HUGE amount of heat in the attic that I need to reflect away from the living space.
So far it has kept the livable space a decent and constant temperature with no wild swings in heat.
What about that foam insulation that is shiny on both sides?
I’m guessing same properties/principles would apply to putting a radiator barrier on a metal garage door?.
How about a video on a spray on radiant barrier?
I don’t think there are more than 3 videos. I might get a bucket of that paint and spray it on my unfinished garage rafters/sheathing to see if it actually keeps heat in, (In Utah, gets below freezing at night) and in the day mid summer, gets over 125 in the garage, place is a sauna).. looking to just keep heat in at this point, now if I can just find me some of that paint, and if I can spray it with airless sprayer..
I love the dog house experiment
Excellent video. Thanks
Thx bro for this experiment
Love from India
Great example of how it works.
In Australia foil barrier is sometimes 'draped' under the roof in thin flexible 'film' sheets.
This is usually a retro fit.
I wonder how much better that would be with 2 air gaps?
The surface facing up could become dusty over time.
Does that dust effect the emissivity on the upper surface?
I think it actually pulls double duty when hung like that. The air gap on top lets it reflect heat (basically its reflectivity is as high as its emissivity is low). Even if the top gets dusty and it absorbs more heat, as long as the bottom is shiny, it still won't emit much downward.
This is just kind of speculation based on physics fundamentals - I basically never hear anyone talking about both features at once. Makes sense to me, though.
I find this counterintuitive, but I don't doubt it is true. I think LP TechShield is mostly for warmer climates. Don't forget to vacuum the aluminum side from time to time as dust reduces the effectiveness. I wonder if money would be better spent getting more reflective roofing. It's odd that my cars "radiator" is made out of aluminum. I guess "convector" was taken.
radiator, radiates heat.
@@FullSendPrecision My understanding of the video is that the aluminum attached to the OSB stops or reduces radiation. Seems weird. I think car radiators work primarily through convection.
@@59seank we’re both right. Think back to how old houses are heated. Radiators :)
@@FullSendPrecision I have fond memories of cast iron radiators. I had a favorite chair near one and it kept me toasty warm as opposed to the leaky single pane windows and barely insulated walls.. It didn't dry out the air like forced air systems.
@@FullSendPrecision Radiators increase surface area to allow heat to pass form one fluid to another faster.
Good job teaching!
Thanks for the video Jordan.
Could you do this with other roof designs, e.g. insulation between the trusses that would be touching the aluminum, or a flat roof with insulation above the OSB, or how about siding with a rain vent behind it so there's less conduction but want to prevent radiation from the siding/roof to the OSB. What if you're in a colder climate and have to keep heat in. Would you install the radiant barrier in the same way in all of these cases?
What about radiant barrier/techshield for walls?
5:06 Would it be correct to say that it's an emissivity heat transfer question?
Thanks
Should have built a third one with no lp at all to see the difference in attic temp
Usimg electric air ventilation as heat exhauster on you roof will do the same for quite cheap like factories have on their roof... to release hot air trapped...
I'm going to be building my house with ICF walls in southern AZ. For the roof I want to do closed cell spray foam in addition to radiant barrier on a metal roof. What is the best way to install it? Is that considered overkill?
Roof deck
Felt or synthetic barrier
Radiant barrier
Purlins
Metal roof attached to Purloins to provide the required air space
Silver side is supposed to go up, but you have to leave an air gap. I suspect that you got a lower temp on it installed silver side down because you put a less conductive material against the hot roof, but had you left an air gap, you would have gotten an even lower temp with the silver side up blocking the radiant heat gain. It needs the air gap to prevent heating by conduction (like an aluminum frying pan on a hot plate).
although that is the optimal installation method for a radiant barrier, i don't believe that is the intended use of this particular product. it seems to be a middle ground, in the event an attic space is finished out for occupation
I could swear that Scott True mentioned you as his duct designer. But someone else designed yours?
Installed backwards… wouldn’t that just super heat the shingles and cause them to deteriorate faster?
I don’t know, but I doubt it. The radiant properties of the material go away as soon as it contacts the shingles. My best guess is that the aluminum will turn into a high-efficiency conductor, pulling the heat away from the shingles into the OSB below. So best guess- it will just be inert?
How about a 3rd dog house with NO Radiant Barrier to prove it doesn't work at all.
If there's no air gap on home 1, the radiant energy cannot disperse, and perhaps it is heating up the shingles even more, causing the difference in temperature...the radiant barrier ahould be reflecting the radiant energy...not sure what its purpose would be in home 2...other then perhaps to keep radiant energy from escaping.
Good information, but this video is longer than it needed to be.
Repeat the test in the North in the winter...
Since no one is saying this you should have made 4 dog houses.
Thought there was supposed to be a gap
My bubble foil comes in both sides shiny. What now?
Staple it to the rafters and let it pull double duty. Top side reflects most heat, bottom side will behave exactly like the down-facing foil here. In theory this should work even better than in the video, because if it's integrated with the board, you don't take advantage of its reflective properties.
I’ve missed you.
Cell phones don't seem to work after install. Bummer
hey Jordan, you are actually pretty good at explaining theories. The first few minutes could be done better, if cut to a white board and explain the theories with drawings instead of standing next to the 2 props. Just like how Steve B does it with his big red. and then you can cut back to the 2 props to prove your theories. Great to see new videos from you. cheers
This is very wrong. Techshield literally has the words printed on it “must be installed with an air gap” it’s not meant to be glued to the underside of OSB. HEB you lift up your second dog house, it says it right there!
3:52 The what?
There's two kinds of smart: The smart that can DO, and the smart that can TEACH.👍
Howdy
Sounds like a bunch of hooplah
5:14 .lmao ..the what now?
What
I don't have a dog.
This is wrong.
LOL 😂 Go back to school Jordan You’re not even close to how a radiant barrier works.
This is a commercial, this is not an informative video ….
Dude, where you been? I thought you were dead.
my guess is there is a housing boom going on and he is charging a premium while times are good.