The Annapolis MD area has had 60+ days of 90 degree weather this summer. My home has a black shingled roof over an attic that has an exhaust fan and a matching intake fan.
Suppose, to reflect the sunlight and heat, I covered this black roof with 4-6 mil plain white plastic sheeting - just during the summer. I would want a sheeting product that breathed to prevent the buildup of moisture and mold.(I have not discussed this idea yet with my aethetically oriented wife.)