Do Radiant Barriers Work? - LP Techshield Review

howdy y'all it's Jordan Smith today I want to talk to you about radiant barriers I'm going to talk a little bit about how they worked and I'm going to show you that it's actually working and then I'm gonna talk a lot about how it works some of the geeky stuff so let's get right into it this is LP Tech shield radiant barrier and what's cool about this is it's a radiant barrier that is integrated into our oh s be sheathing so the board looks like this we have OSB and then it has this aluminum barrier right there that keeps heat from radiating into the space so a little bit about how it works is he conducts in three ways convection conduction and radiation or I should say heat transfers in three different ways conduction convection and radiation so this takes care of one part of our heat transfer and that is radiation but only if you do it right so now I'm going to show you that it actually works I've got an infrared thermometer right here now infrared thermometers aren't great at showing what temperature's things actually are but they are great at showing how much radiant energy infrared light is coming off of this board here so we're at 82 degrees on this board right now it's a Texas winter day overcast so it's not the greatest day to be showing this but the time the summer rolls around this will all be covered up and I think it should show you what I'm wanting to show this is my roof deck on the same side so I just tested over there the westerly facing wall now I'm going to show you here on a westerly facing roof and I've got 72 degrees don't you see that 72 71 and a half 72 degrees so we have a 10 degree Delta on a day where it's really not all that hot out here so just imagine what it's actually doing in the summer we've got a westerly facing wall which isn't taking near as much radiative energy as the and we still have 18 degree Delta now let me talk a little bit about how it works so like I said three different ways that heat is transferred we have convection conduction and radiation radiation is how we get the heat from the Sun right in space it's a vacuum so there's no way for that heat to get from the Sun it's to the to the earth except through ultraviolet light so it's actually sending ultraviolet light as heat into our atmosphere and it heats up our air and our water and those transfer heat by something called convection so as those move around as the water flows and as the air flows we get the hot air particles or water particles moving from one point to another transferring that heat with them the other way that it works is through convection and that is very important in building assemblies because right here where we have this rafter touching our roof deck we have convection right here so even though we have the same aluminum backer it doesn't do us any good right here at this rafter because we have negated our radiant energy and we are conducting our Heat straight from the roof deck into here that's why things like advanced framing which this roof is not framed with but if we can spread these rafters out further than we have less conduction through our rafters and a radiant barrier can do a good job the last thing that you need to keep in mind is depending on how you insulate this you can totally negate how your radiant barrier works so for example in this cavity here we're going to be doing fiberglass insulation I've upgraded to 2 by 10 rafters which allows me to have my r-value that I need in my roof while still maintaining an air gap between my insulation and my roof that that air gap allows this radiant barrier to work because it's not going to emit the heat into the cavity it's going to turn around and reject it out the outside but if I took my insulation and I put it all the way up against here now I'm conducting the heat from my roof deck into my insulation if I do this and then I go with a spray foam here if I came and I spray foamed all this well I shouldn't use the LP tech shield product because it's not doing any good as soon as I spray foam all the way up to there it's conducting the heat from the roof deck into the spray foam and the spray foam will then reradiates or conduct the heat into the living space below so if you spend the money for a a radiant barrier make sure that you build the whole system to take advantage of the radiant barrier don't just put it up there and hope that it magically happens cuz that's not how it works you have to have an air gap on the backside of this in order for the radiant barrier properties to kick in there's a whole lot more about heat transfer that I'd love to get into but I'm out here on the jobsite and can't really get into it if you want to see a video more about heat transfer comment below let me know thanks so much for watching subscribe if we've earned it go follow us over on Instagram at Jordan Smith build at Smith house if you have any other questions about how we built this house or a specifically LP tech shield comment below and we'll see you next time on Smith house [Music]

Channel: Jordan Smith

Views: 484,223

Rating: 4.7866845 out of 5

Keywords: radiant barrier, does radiant barrier work, how does radiant barrier work, emissivity, insulation, sprayfoam, fiberglass insulation, hvac, energy bills, how to reduce your energy bills, hot attic, ventilated attic, conditioned attic, building science, how to build your own home, building your own home, diy insulation, diy homebuilding, the build show, rrbuildings, matt risinger, heat transfer, construction, dream home, home design, design build, smith house, jordan smith builds

Id: qaUOp_EbUu0

Length: 5min 56sec (356 seconds)

Published: Fri Jan 17 2020