In the middle of a very well written article about keeping cool and lowering energy bills contains 4 paragraphs about window films:
The same holds true with 3M’s Prestige series of performance window films, which preserve the view from inside the home. They allow natural light into the home while blocking up to 97 percent of the sun’s heat.
Prestige comes with a lifetime warranty against bubbling, peeling and color change. It costs about $9 to $11 a square foot, depending