Before the yo-yos in Albany NY decided to have inspection stations enforce window tint laws, I admit, I am a bad boy here and have had all my vehicles windows tinted except the w/s. Tint was not the deep dark limo tint, but more like a med that you still could see in albeit a lil dark. Anyways, the temp diff between the w/s and doors was immense. Could definitely feel the difference and A/C worked sooooo much better. Could actually put arm on door rest while driving and not get "baked".
There is a tint made by 3M that's darn near clear as a bell w/ some small degree of darkness to it, but NOTHING like what auto stores or 99% of tint shops sell. Keeps 99% of UV rays out and yes some heat is transfrred in, but again, nothing like if you have nothing on windows. I have it on my truck (think it's the 70% rating) and you'd be hard pressed to see that the windows are tinted. Does a bang up job as well as the dark tints, but clear. You'll have to go to 3M's website to find dealers near you and they are not everywhere's which could pose a problem if you want it done. So if you have dark windows on your coach now, may want to consider this option.