Radiant Barrier Department Of Energy Lab Test Results - (Understanding Reflectivity vs Emissivity)

Depending on which side of the double-sided product the air gap is one, AtticFoil will either use reflectivity to reflect heat, or emissivity to block it. Radiant barrier decking (ex. TechShield or Solar Board) uses emissivity, where as stapling AtticFoil to the bottom of the rafters uses reflectivity and is more effective at reducing heat transfer.

[Earth]

When the foil pressed up against the hot surface, heat transfer happens 100% by conduction. When there is an air gap between them, the heat transfer happens by radiation and convection (and conduction from the foil to indoor air). Since the foil is so good at reflecting thermal radiation, the latter works better. Even though I knew the physics behind it, it never occurred to me until I watched this video. So thanks a lot!

[jed]

Your vid told me EXACTLY what I needed to know before I put this stuff up. 20% better is a big difference so I'm going with reflectivity by attaching the foil to the inside of the wall sheeting I'm installing.
I can't believe people are watching this and THEN asking the questions you just answered.

[pbpyro]

Got my first house and i want to make it as comfortable as possible. Im going to buy this. Nice

[dennismyname]

Thank you, just thank you.. took me a long while to get my head around it

[petehendi]

Hi Ed... Thank you, thank you, thank you! I've been seeking this answer and it's been driving me nuts. I'm a educated guy, and even a bit of a science dork, so I completely understand and conceptually GET the difference between the three main forms of heat transfer: Radiation, Conduction, and Convection. What I did NOT get is how it was possible for those products like LP TechShield to have ANY effect at all. If I'm standing 1ft away from a large campfire and hold a sheet of foil in front of me I'll be cold, cuz I'm blocking virtually all of the radiant heat of the fire, but if I wrap myself in that foil tightly in that foil I'll cook, because at that point the foil itself will heat up and through contact it will heat me up. So how can Techshield have an effect. I finally understand that it HAS AN EFFECT, just not nearly as powerful of one.

I live in Atlanta, GA and we are about to build a home (I myself am a roofing contractor). I know there has been case studies done on Techshield type products and they do seem to (w/ minimal effort) have a decent and measurable effect. I have not costed out the product to see how much more than regular OSB it costs, but I imagine it's not a HUGE difference. I'm betting a guy like you has read the studies and has done the math... Since attic foil has even a bigger effect I absolutely plan on using that (even though it does take more effort too). If I'm building from scratch and can afford the increase in material cost for the decking, do you think I should use both Techshield AND use attic foil?? Or should I skip the techshield type stuff and ONLY use the attic foils systems?

What are your thoughts about batt insulation vs. blown insulation (I watched your video about fluffing and would be sure to purchase by units, not inches)? I worry that blown insulation, even with baffles, may clog up my intake vents, it gives a more uniform coverage too.

[RyanJohnsonD]

That pretty much answered my questions.

[FloJoMoJo]

Hello! My husband and I will be installing this in our attic, and we're wondering if stapling 2 layers instead of just 1 would increase the benefit further. Has AtticFoil tested this at all? Thank you so much for your videos by the way. They've been incredibly helpful and informative!

[davebean]

Are there any issues with using both emissivity and reflectivity? Our roofing already has a silver lining under the wood and above our rafters. I'm considering adding another reflective barrier under the rafters. Our ducts are in the attic and we are in a warm Texas climate. Thanks.

[The_Absurdistt]

@AtticFoil Regarding using radiant barrier on walls... Should an air gap be present between the insulation and radiant barrier and well as between the radiant barrier and sheet rock?

[johnmisenheimer]

Great content. Quick question for you. My newly built home has the aluminum built into the roof decking already. Our second floor AC unit constantly runs during the summer time. Would it be beneficial to add your product to the boards to create that air gap? Would the benefit be cumulative? Thanks!

[MitchellVamos]

What happens if you have a water leak in your attic and the rafters are foiled up? Won't it be undetectable since it's invisible?

[adammacer]

OK, so looking at emissivity tables youcan see that foil emissivity is 0.03 and wood is 0.9. So foil is going to radiate a tiny fraction of the heat that the bare underside of OSB sheathing would, but there is still going to be direct transfer of heat by conduction to free moving attic air that will convect. Is radiated heat really THAT much of a component in this situation?

[davidcallowayjr]

Hello, Is it ok to add R-13 piece insulation between the outside wall and the foil when the foil is placed in the emissivity heat (attic foil is nailed on the rafters/studs on the inside of the house)?

[UltimateMMAFan]

with attic foil on the rafters, how does heat fare with it coming up the rafter channels (that air space) and only has room to go out of whirlybirds? I know a ridgevent is already designed to where it'll go straight out the exhaust but with whirlybirds it seems like alot of heat will recirculate back through the attic and move out sooner or later but not as efficient as a ridgevent or on a roof with hips. Please let me know what you think

[ocrun]

would there be any benefit to doing both radiant barrier decking plus foil barrier with an air space?

[ajsemtb]

Ok, so if techshield on the bottom of OSB blocks 30%, and the reflective foil blocks 50%, then why aren't we seeing foil backed drywall or gypsum board to reflect on vaulted ceilings or sunny walls? Seems like there's a market for that where you can't install the foil to a vaulted ceiling. thoughts?

[justinbarney]

I have a 40ft. shipping container in the northern South Carolina-area, approx. 10 miles from the beach. My plan(for the exterior) was to paint the outside with automotive reflective paint. Then (for the interior) was to put the reflective material directly to the wall AND then put R19 insulation between the studs. Is any of this wrong? ...should I consider a different approach?

[ESLinsider]

Is that the same with cold? Like if it's cold outside and you leave that air gap will the cold be reflected back outside?

[eddygoodwin]

have you tryed putting the foil on top of the insulation in an attic and putting it under the rafters?

[masterdebater]

If I go reflective with airspace on hot side in a small 8 x8 shed with radiant Barrier is that enough to call it insulated being on a budget?