Congrats as doing all that work above your head is not easy on the arms, or neck, or back!
I've been spraying 2 component spray foam on my crawl space walls and its tough work.
as far as this, IIRC
Quote:
Inside air film below flooring = R-0.68
R value of 1/2" air space = R-1
Inside air film above EPS (one surface reflective) = R-2.23
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IIRC, You only calculate an air film r value when its against an open space, not in an enclosed area - you get one on each side of the total assembly. I believe you need at least a solid 3/4" to 1" to get R1 for air. You reflective surface going up looks about right, although I've always read 3/4" was required for an airspace.
As another comparison I've read a radiant barriers R value going up is about the same as standard eps insulation with 3/4" air space, so R4, so you should have a little under R3 for that radiant space.
Really the air seal is where your making your money.
I'm planning on trying to spray foam my underside for about an inch, and then apply a roll radiant barrier against it and around the joists, for roughly R20 in the winter. Problem is it has to be clean otherwise the spray catches on everything like spider webs or specs of dirt or sticking out nails.
thanks for the details and pics