Found an inexpensive solution for turning a hot garage into a shop. If your garage is like mine; hipped roofs, full sun, and no insulation, your problem is radiant heat coming through from above. Traditional insulation is too expensive and may cause moisture build-up issues. The solution is to reflect the heat back upward before it gets into your shop space, and vent it up and out. If you do this, even a relatively small portable air conditioner can keep your shop space reasonably cool. Here's the set-up. I bought wide and narrow rolls of cheap reflective roll insulation ( not perforated) at Lowes. First, I ran a narrow (18 inch?) strip of reflectix from the top of the wall to the ridge board STRADDLING (not touching)the diagonal hip rafters, and stapled it to the common rafters alongside. If you span the hip rafter, you create 4 air spaces that the common rafter spaces can spill hot air into. I then covered the common rafters with wide reflectix. In all cases, I left a small (1 inch or so) space at both the top and the bottom of the runs. The final step was to vent the gathered hot air out the peak of the roof. In my case, I rebuilt an existing cupola that sat on the ridge board to cover holes cut alongside the ridge boards. You could also use a modern ridge vent. My garage is in full sun and even on a 95 degree day, I have not needed a vent fan. Cheap, quick, and works great.
