It's always best to keep the heat out in the first place. I use a Sunguard shade on the exterior of the windshield and then I place those folding reflective shades underneath the the Sunguard shade. That keeps the sun from penetrating the windshield and therefore the infrared heat out. I also use the privacy shade for additional insulation.
I have painted the skylight in the shower so that virtually no light gets in, thus eliminating it's greenhouse effect. I first painted it with a dark brown to block light penetration and then covered that in white paint to reflect the light and heat.
When it's really hot I keep the slide outs closed, thus reducing the space that needs to be cooled by the A/C.
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