Radiant barrier OSB on a roof, foil side out
I have searched high and low for an answer to this question and keep coming up short. I hope someone here can offer some insight. We are building a 2 story backyard “bunkhouse” that will be used for the occasional overnight guest, but primarily for additional play and work space. The building is being built with a slant style roof with what is essentially a cathedral ceiling (no attic space)
We are in zone 2 not near the ocean, so mostly a cooling climate though winters can get into the teens occasionally. I would like to utilize radiant barriers in the construction. In the walls I plan to use it as recommended with the foil facing out, and creating an exterior airspace with furring strips, creating a rain screen with a combination of board and batten and metal siding.
For the roof however I am less sure. What I would like to do is face the foil outside as well, (I know this is not the typical installation) if it faces inside, we would be very limited in our ability to add insulation to the roof (no attic) and maintain an air space. Would it make sense to use the radiant barrier OSB for the decking with the foil side facing out using a metal roof over purlins to create an airspace? I feel this would then allow me to do spray foam on the underside of the roof, or use foil faced foam panels with the foil side down leaving a 1/2″ airspace between the rafters and the underside of the ceiling material.
My primary concern is reduction of heat gain in the summer, but the ability to insulate against heat loss in the winter is important as well.
I can not find any information on this type of roof system, which has me concerned that it may be a poor idea. Any input would be greatly appreciated.
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