Here in Michigan we got hot summers and cold winters. I can deal with the shop being 55 degrees, but not 85 degrees. The shop is 725 sq ft and on the second floor, R19 in the walls and R38 in the ceilings.
I'll admit I have a small window AC , used most summer days, 2 ceiling fans, used fequently, and a ceiling exhaust fan, rarely used. My house and shop has a roof framing detail with 2x4s running flat and parallel with the tops of the rafters providing a larger surface to sheet and a 1 1/2" deep flange on each rafter. This provides an AIR GAP continuous along the entire roof surface, so the air rising from the soffit can move upward and out the continous roof vent visible below. This method I believe was used in the building of ice storage buildings back when... and was called an ICE HOUSE roof.http://en.wikipedia.org/wiki/Cool_Roof
This was all I could find in quick net search. The 48" long 3/4" thick foam panels are foil covered with household aluminum foil applied with spray adhesive to reflect the radiant heat that penetrates the shingles and sheeting. They sell an aluminum foil paper
to acomplish the same thing, but it's a PITA to work with, hold, staple, stretch etc. I used that on the house, but then I used the foam and foil on the garage addition. BTW, applying the foil is also a PITA. The spray goes everywhere and the foil sticks to your fingers first, the foam second and it never lays down on the foam where you want it.