No and no...........I think.
This stuff is incredibly tough. I only have the 16 mil stuff and not only use it to cover my "temporary" greenhouse framing for my plumeria during the fall and winter months but also used it to cover my screened-in porch during those months.
My greenhouses get so hot from June through September, that neither are much good for anything but starting seeds and rooting my plumeria. I keep the doors wide open, all the vents open, and use 70% shading, but the greenhouses still get really hot. I don't really think there is much difference in the heat, whether I had only the polycarbonate panels or those panels are covered in solar blanket material. Fans surely help, but still, the fans I run just moves hot air around.
They are called hot-houses for a reason I guess.