Reflective side in or out?
I am covering my home with 2 layers of 2 inch rigid foam. The outer layer of foam has a reflective side and a non-reflective side. I live in Wyoming, zone 6. I am using furring strips covered with a combination of Hardie Plank and metal. Should I turn the reflective side in or out? The North and West side will receive full sun during most of the year. Thank you for your responses.
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Reflective side faces the air gap, which give it another ~R1 of effective thermal performance.
How does the NORTH side receive full sun in the northern hemisphere, given that you're below the Arctic circle? :-)
The aluminum facing can act as a useful radiant barrier, but only if it faces an air space. In your case, the outermost layer of rigid foam should have the aluminum side facing out, toward the air space.
A 3/4-inch air space with a radiant barrier on one side will add about R-1 or R-2 to the R-value of your wall assembly -- not much, but something. It's certainly worth pointing the aluminum in the right direction. It's also good to know that the aluminum side is much easier to tape than other facings -- so be sure to tape the seams of your rigid foam.
Sorry Dana. I meant the South side.
It would seem to be that if you use the foam facing out, you can use Tyvek or housewrap tape rather than a more expensive product to tape the seams.