These thin sheets of reflective film on the inside surface of window glass greatly reduce heat gain. Window films reflect much of the sun's heat before it passes through the glass. But, the glass itself still gets warm. The film also reduces the heat flow from the warm glass to the inside of your home. In winter, the film blocks heat flow from the inside to the outside, making your home more comfortable.
Window films are effective and easy to maintain.
There are many types of window film's on the market. Look at several types before you buy one. The films come in many colors. The most common are bronze and gray. Also think about how things will look through the film.