Bluescope Zacs

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Re: Bluescope Zacs

Postby Sometimewoodworker » Fri Sep 08, 2017 8:50 pm

Saffles wrote:
Andyfteeze wrote:well saffles, if it is foil, its rather on the thin side, as you do in thailand. I wouldn't even consider it after my experience. Roll up alfoil as in glad wrap type product is far and away stronger and thicker than the crap I saw.


You can call me Mark.

It looked nice and yes it is thin. All aluminum products are great at reflective insulation but not with heat transfer. Also aluminum foil in high heat high humidity environments will oxidize and be practically worthless in time.

Concrete tiles are strong and thick but do not stop heat transfer. A 5 kilo per meter Colorbond roof is cooler (to the house) than a 50 kilo CPAC roof.

http://www.sigmalabs.com/blog/reflectiv ... d-r-values

Mark


It isn't the reflective factor that the aluminium coating works on when correctly used in Thailand. It is its extremely poor radiation of heat. The makers of the film well understand the oxidation problem and the problem of keeping as shiny a surface as possible, that is why the aluminium has a plastic coating on it.

FWIW After 5 years the extremely cheap aluminium foil over my parking area is showing no sign of breaking down.

The link you give is advertising the product of that company so some of it is of questionable value. It does note that the way aluminium foil should be used in Thailand and the foam plus foil glued to the metal roof has no R value.
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Re: Bluescope Zacs

Postby Saffles » Fri Sep 08, 2017 9:47 pm

Sometimewoodworker wrote:
The link you give is advertising the product of that company so some of it is of questionable value. It does note that the way aluminium foil should be used in Thailand and the foam plus foil glued to the metal roof has no R value.


Of course companies would "bend the truth" to their side. I read numerous studies that were quite comprehensive on the subject (but long winded) and this one wrapped it up pretty easily.

The studies show that a REFLECTIVE barrier has zero r value and to be a RADIANT barrier:

"Remember, to be a radiant barrier, the aluminum foil must be installed facing an airspace. If there is no airspace, the foil acts as a conductor and quickly passes heat by conduction from a hot surface to a cooler one." (Florida Solar Energy Center, University of Central Florida/U.S. Dept. of Energy)

The PE foam (r-3) would act as both an airspace and a non-conductor of heat. Is it the best material available? Not. Does it appear to work? Yes. Would it be best to put the foil/PE a few cm away from the roof? Yes. Is it possible to put an aluminum barrier a few cm away from the roof covering the entire roof surface area? I do not know.

Mark
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Re: Bluescope Zacs

Postby Sometimewoodworker » Sat Sep 09, 2017 6:46 am

Saffles wrote:
The studies show that a REFLECTIVE barrier has zero r value and to be a RADIANT barrier:


While there certainly are REFLECTIVE barriers and RADIANT barriers, and the same product can be both and both at the same time, they provide protection from heat transfer in opposite directions.

The difference can be confusing, specially when they are combined with insulation of some kind.

However in general reflective barriers degrade rapidly in Thailand due to dust accumulated on the surfaces, as they have to be put on top of the ceiling facing up. Radiant barriers do not have this problem as they are under the roof facing down.

This topic has been discussed at length at the link under

http://www.coolthaihouse.com/forum/viewtopic.php?f=40&t=4476
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Re: Bluescope Zacs

Postby Saffles » Sat Sep 09, 2017 9:30 am

Agree,

The original"question was... Did anyone have experience with Bluescope Zacs 90? Answer not given.

Case closed.
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