When it comes to blocking solar heat in order to reduce load on A/C, covers and insulation on the outside of windows is far more effective than blocking it on inside of window, even if it "feels" like insulation on inside of windows is doing a good job.
Once solar energy comes through windshield or window glass, even if it is blocked by a barrier, much of that heat will end up trapped inside the RV anyway due to air movement. You won't see it or feel the radiant heat of the sun on your skin, but much (sometimes most) of the solar heat will end up having to be removed by the A/C. That in return will make inside temperature warmer because A/C can't keep up.
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