I know that you can have special anti-uv window film put up to filter out the bleaching effect of the sun - one of my client's does this.
Be careful to pick a good company to do this though - he's always telling me there are some cowboys who don't do as good a job as he does!
You shouldn't be able to see the film at all, there should be no bubbles or gaps around the edge, and it shouldn't be reflective, just totally clear. If it's any of those things it's either poor quality or poorly applied.