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-   Insulation and Radiant Barriers (http://www.houserepairtalk.com/f106/)
-   -   Radiant Barriers, is it a sham? Logic inside... (http://www.houserepairtalk.com/f106/radiant-barriers-sham-logic-inside-11408/)

chaluska 05-25-2011 09:39 AM

Radiant Barriers, is it a sham? Logic inside...
 
Ive been looking into it, seeings as i'm going to have to do a lot of work in the attic, i would rather get all of the hot stuff done at once. I will be spraying in f-glass / cellulose insulation which i have calculated out to 10$ per bin (40 sq ft), and i will need approximately 40 bins , so a 400 dollar investment with free blower rental should get my house to a high R rating, to cope with these Houston summers.

http://www.homedepot.com/catalog/pro...a634ca_400.jpg


but first i would like to address the radiant barrier potential.


I'm basing this off of this type of foil insulation. which a contractor pack of (50) 24"x48" sheets is 200$ at home depot. assuming i would need at LEAST 2 packs (if not 3) to do my attic, im looking atleast a 400$ investment. for what i have heard is a r-value of MAYBE 1.

http://www.homedepot.com/catalog/pro...43e847_300.jpg

I understand there are several types of radiant barriers, but for this discussion, lets assume its the foil type.

Now I can understand the theory, that the aluminum "foil" backed insulation reflects alot of the heat rays back out. but when its put installed beneath the plywood, and overstacked shingles, what rays are really penetrating that far in.

mainly for the cost of the insulation, if you were to have houses, with identical R38 insulation sprayed in in the attic, and only one house had the radiant barrier installed.

identical houses, in identical correlation to the sun, would there be any notable difference? it seems like its extremely expensive (in comparisson) for a very little increase in cooling.

anyone have any input?

It almost seems like snake oil to me. it wont serve any purpose other than piece of mind.

nealtw 05-25-2011 05:53 PM

Not sure about the foil but I would spend more time and money on venting the attic.

AndyGump 05-28-2011 06:49 PM

It is my opinion that a radiant a barrier is an excellent investment in warmer climates like your and mine.
Invest in the least expensive barrier that is available to you. They will all pretty much work as well as any other.
A RB works by reflecting radiated heat from the sun and in sunny climes that is a distinct advantage in energy savings. For the colder climates it is not such a blessing as you would like to have the sun's energy radiating into the house.

Andy.

saltbranch 05-30-2011 06:18 PM

I am by no expert on this by any means. I did just have a new roof put on which required redecking the house. We went with the R barrier backed plywood plus ridge vents, I also installed R-30 bats in the roof and R-13 in the walls. We had smoke damage from a kitchen fire, all the sheet rock was out when I put in the insullation....anyways it maybe a combo of all the above installed , but the house is cooler during the day. Just today my wife commented on it being cooler when we were working on the floors.

chaluska 05-31-2011 11:17 AM

Quote:

Originally Posted by saltbranch (Post 57502)
I am by no expert on this by any means. I did just have a new roof put on which required redecking the house. We went with the R barrier backed plywood plus ridge vents, I also installed R-30 bats in the roof and R-13 in the walls. We had smoke damage from a kitchen fire, all the sheet rock was out when I put in the insullation....anyways it maybe a combo of all the above installed , but the house is cooler during the day. Just today my wife commented on it being cooler when we were working on the floors.

see, there is the issue,

you had ALLLL of that insulation done at once, so its impossible to tell if just the R-B backed plywood helped or not.

if you went from the original insulation, to R-B backed plywood and it made the difference, that would be more of what im trying to find out.

nealtw 05-31-2011 04:54 PM

Radiant Barrier Testimonials from actual customers

It make for interesting reading.

JPLSTER 06-09-2011 09:24 AM

I live in New Orleans and I am a contractor. After hurrican Katrina most of the houses were completly gutted. No insulation, no sheetrock walls, no windows, no cielings just rafters, joists and stud walls with an intact roof. There was an idendical house next door except it had a foil heat barrier stapled to the roof rafters. The carpenters and I took our lunch breaks over in that house because it was much cooler than the house we were working in. In the house that I worked on, you could feel the radiant energy hitting you through the roof. The sun heated the roof which heated the underlayment which raidated on me 12ft below. I could feel it and it was HOT! That has convinced me that, a foil heat barrier helps greatly.

chaluska 06-09-2011 12:42 PM

I have found a pretty affordible source for radiant barrier material, so im going to pick up about 2000 sq ft, and do that prior to the insulation, so i wont be rolling around in 12" of cellulose

nealtw 06-09-2011 05:34 PM

So you will be able to tell us how it works. Take the temp up there before and after on a simular day.


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