Radiant Barrier Under Shingles Won't Work Without An Air Space

[bigbadblue4u]

Great Info Thank You

[thermaldog]

yes, good video...this is very important. Unfortuanatley the insulation companies often sell substandard products and systems and dont stress the importance of undertanding heat transfer physics.

[AtticFoil]

@thermaldog Thanks. Facts and laws of physics don't lie.

[baristeve]

wouldn't RB still reflect conductive heat technically as long as it's not being touched on both sides?

RB pre-construction is installed directly onto the plywood decking which would mean there's no airspace except underneath where there is obviously no radiant heat emitting.. also.. doesn't aluminum reflect heat by blocking the molecular friction process? which would mean that it technically blocks conductive heat that forms by radiation through the decking.

[AtticFoil]

@baristeve Thanks for the comment. Technically, you cannot "Reflect" conductive heat...only slow down it's transfer.

RB decking with aluminum does not "reflect" downward heat. It does as you state correctly create a low emissivity surface (slower molecular friction) which greatly reduces that ability of the stored energy (heat) in the roof deck to convert to radiant heat. The foil does not block conductive heat since by the time it reaches the foil it has already passed through by conduction.

[MagrinhaSkinny]

Thank you your videos are great!

[Znobyrd]

What effect does laying a radiant barrier over the top of blown in cellulose have on heat loos / heat gain? Thanks.

[AtticFoil]

@Znobyrd Look for my video "Attic Insulation & Radiant Barrier In Cold Climates". This video explains the benefits of laying AtticFoil directly over the existing attic insulation.

[Denniss7420]

Cool illustration and explanation. Thanks,

[faithsno1dad]

He is 110% correct in this clip. When he speaks of two types of ways heat will transfer/travel, conducting and radiant. Heat will transfer through just about anything, giving the right situation. Having the distance and space is what is key here. I am and Insulation Installer by trade, and by chance I found this clip and even took my time out to view many other clips that AtticFoil. made, he is spot on. I done this phase of insulation many times over,with stellar results and feed back.

[AtticFoil]

@faithsno1dad Thanks for the kind words.

[faithsno1dad]

@AtticFoil It is my pleasure.Just keep putting out a great product, because more and more people are hearing about this phase of insulation as it is still some-what new to the public, compared to Aerospace.The cost of this type of insulation/FOIL, to Spray foam and other INSULATION MATERIALS, is by far cheaper at the same time giving almost a 100% better advantage.The attic foil along side a professional insulation installment done with quality, will in fact yield results almost immediate.

[monkeyman1140]

Just wondering, but would a combination radiant barrier on rafters combined with another layer on the insulation be useful for both winter and summer?

[AtticFoil]

@monkeyman1140 It will provide some additional benefit. Just remember the first layer will provide the biggest impact.

[catrashoo]

very interesting thanks.

[thepiedmontrenovator]

Does foil backed osb work as a radial barrier... the osb foil backed is installed foil down... so you have at least a half inch or so between the shingles and the foil?

[AtticFoil]

Foil back decking actually works off the emissivity quality and not the reflectivity quality if installed with the foil facing the attic. The attic IS the required airspace. Emissivity is the ability NOT to convert energy into radiant heat. Every surface emits radiant energy at a different level. By putting the foil on the bottom of the OSB, it changes it's emissivity quality just like wrapping a hot potato will keep it hot longer by not emitting as much heat.