I need a name, website or whatever for a foil-faced roof decking and some opinions on usefulness for my application. My energy auditor mentioned this but did not know the mfgr. or specifics. This is a 3-layer tear-off so I am not planning to do this myself but I have an experienced roofer in mind who will supply whatever I specify. Anyway, we have an unvented, sheetrock-finished cathedral ceiling, icynene-insulated, no vapor barrier, 2x6 rafters 24" OC and four Velux roof windows. I want to reduce the summer heat penetration. I brought up the idea of adding a roof deck above the current decking, with a 1.5" air space and adding soffit and ridge vents. The auditor said that wouldn't have much payback but I should find out about this other stuff that would presumably just be nailed to the existing decking. Current deck is 3/4" boards spaced about 1/2" to 1" apart, so they will not support asphalt well on their own anyway. Current roofing is original 1920s cedar shingles then (presumably 1950s or 1960s) asphalt, and on top early 1980s dimensional asphalt still in pretty good shape. Roof pitch is about 9/12.

I am trying to calculate a roof slope on a shed I am going to build. The dimensions of the shed is 8 ft. at the front rising up to 14 ft at the back. The shed is 20 ft from front to back.