Thanks so much for taking the time to share your experience and for experimenting with Renshade on different windows Yasmin.
You’re spot on that stopping the sun before it reaches the glass is the gold standard for summer heat control. Renshade, however, is purposely designed as an indoor, renter-friendly, cost-effective solution for when exterior shading isn’t possible. It isn’t waterproof for outdoor use, so weather exposure (especially rain) will degrade the material over time. For that reason, we don’t recommend—or warrant—installations on the outside of the window.