Radiant Barrier Foil Under New Hardieplank?


Old 06-22-06, 01:36 PM
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Join Date: Jun 2006
Posts: 2
Radiant Barrier Foil Under New Hardieplank?

Hi guys, I am re-doing a 1901 frame row house in Richmond, VA. It has 3x6 studs and R-11 insulation currently in place from 1991. I am switching over to a heat pump, have ordered pella low e windows and am about to replace the siding with hardieplank cement siding. Right now the house just has the fiber boards over the frame/R-11 insulation. My guess for best energy efficiency is to use PRODEX or similar radiant foil barrier (R14.5) and then put siding overtop. My concerns are that there will be no air gaps on either side and some of the other threads claim these RB's lose effectiveness quickly. Any thoughts/ideas are greatly appreciated!!!!
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Old 07-21-06, 01:47 AM
Join Date: Sep 2004
Location: Canada
Posts: 71
I really don't see how anything can reflect when it is covered. If there is no airspace then you have direct contact which means there is a direct path for heat to transfer through both the board and foil.
I suggest you look into ceramic insulation coatings however look beyond just the single reflective ones or you will get the same results as the foils. There are second generation ceramic coatings that improve upon the ones that came out with just the single ceramic as they include multiple ceramic types which address all three forms of heat transfer. Standard insulations are effective at addressing only two of the three forms of heat transfer.

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