I need a film that will not reflect sunlight onto the deck and railing to prevent heat damage. Will this film work? Or is there a better film that will serve this purpose?

Yes, this film or any dusted/frosted film will work well to prevent the reflection. Just be sure to install it on the exterior and not the interior. Here is a link to all the films you can use that we would warranty for 3 years: https://www.decorativefilm.com/exterior-frosted