Once I took the time to actually read the instructions and learned that there was a protective clear film on the back to be removed first it went on as slick and easy as proclaimed. It does not darken the room. Our weather is too temperate at the moment so I can’t speak of the heat￼cold reduction factor. When the sun is in the right position or even car headlights, they do add prismatic effects. I would buy this again especially on sale.