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Old 12-15-13, 10:57 PM   #388
berniebenz
Helper EcoRenovator
 
Join Date: Apr 2012
Location: Gardnerville, NV
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Default "bubble crap"

Quote:
Originally Posted by jeff5may View Post
The vapor barrier on under-floor insulation should always be placed close to the floor. The concrete barrier foil in the above post would work. In practice, I have seen contractors spray silver "aluminizing" paint on the kraft-paper-side of fiberglass batts before installation to help reflect radiant heat. These same guys have nicknamed the "space blanket" type insulation (ecofoil, prodex, reflectex,etc) as "bubble crap". I tend to agree, having lived through the drama of reflect-x having to revise their lofty claims after ASTM testing revealed their product to have an r-value of just about 1.
I agree!
Look at the emissivity of the low temp 80 deg. subfloor radiating downward to its receptors, looking at either a properly placed and transparent bubble and aluminized reflective film or, in its absence, to a black PE sheet crawl space ground cover, neither of which are high efficiency reflectors of this long wave length radiation. This downward radiant heat loss difference among recieving surfaces is trivial, relative to the total useful upward heat loss, being radiant, conductive and convective. It exists, but is trivial! Not worth much to reduce. Do a cost / benefit analysis.
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