There have been many post on this Forum about temporary spray booths built using plastic sheeting, some inside garages, under carports, even outside such as mine. I took the design elements of some of these and incorporated them into mine. None of the problems I encountered have been discussed on this Forum to my knowledge so I thought my experiences might be of benefit to others comtemplating a similar setup. The main point I'm trying to make is that for whatever the reason, IR I assume, the plastic amplifies the heat raising the temp. of the parts to be painted well above what I expected and well above what they would have been had I not used the plastic and just painted outside in open air.
I had hoped to avoid the expense of lights but I now think that cannot be avoided. If I were to do it over again I would build this booth inside my garage with lights along the sides and top. Another alternative might be to build outside but use the construction foam sheets available from Home Depot. The one I'm talking about are blue in color and 3/4" thick by 4'x8' and use duct tape to seal the seams. Still thinkin' about it.......