Some of the absorbed heat, however, passes through the window by conduction and reradiation. Reflective glass has been coated with a reflective film and is useful in controlling solar heat gain during the summer. It also reduces the passage of light all year long, and, like heat-absorbing glass, it reduces solar transmittance. Plastic glazing materials acrylic, polycarbonate, polyester, polyvinyl fluoride, and polyethylene are also widely available. Plastics can be stronger, lighter, cheaper, and easier to cut than glass.
Some plastics also have higher solar transmittance than glass.
However, plastics tend to be less durable and more susceptible to the effects of weather than is glass. The simplest type of storm window is a plastic film taped to the inside of the window frame. These films are usually available in prepackaged kits. Although plastic films are easily installed and removed, they are easily damaged and may reduce visibility. Rigid or semirigid plastic sheets such as plexiglass, acrylic, polycarbonate, or fiber-reinforced polyester can be fastened directly to the window frame or mounted in channels around the frame usually on the outside of the building.