When I built my shop three years ago (stick built), I insulated the ceiling and walls with R-30 and R-13, then drywalled it, and used Low E double pane windows. One thing I did not do, was to install the roof sheeting with the foil thermal barrier.
Right now, I am building an addition on the house, and we used the thermal barrier roof sheeting. It is OSB 5/8" with an applied foil on one side. The inspector recommended it, and said it will keep the attic space 15 degrees cooler in summer. We are just wrapping the building now, for stucco, and it really seems to work. The insulation is not even in yet, and the building does not seem to be very hot near the roof.
It only costs 2 or $3 a sheet, total cost less than $300. Wish I had it in the shop.
Rick Potter