Energy-efficient window film targets the heat that moves through glass, helping rooms stay more comfortable when the sun is strong and easing the demand you place on cooling equipment. For Perry Hall homes with large windows, sunrooms or an unshaded rear elevation, that often means fewer rooms you avoid in the afternoon and a steadier temperature through the house. Film also cuts glare and ultraviolet at the same time, so one treatment addresses several complaints at once. Compared with replacing glazing it is a far smaller project, applied to the windows already in place, though the gain depends on the film, the glass and how the house is oriented. An installer should look at your existing glazing before recommending a product.