The coatings reflect between 40 percent to 70 percent of the heat that is normally transmitted through clear glass, while allowing the full amount of light to pass through to the inside. Heat-absorbing glass contains special tints that allow it to absorb as much as 45 percent of the incoming solar energy, reducing heat gain. Reflective glass has been coated with a reflective film and is useful in controlling solar heat gain during the summer. The passage of light and solar transmittance is reduced with reflective glass. Plastic glazing materials are available as acrylic, polycarbonate, polyester, polyvinyl fluoride, and polyethylene.
Some plastics have higher solar transmittance than glass.
They tend to be less durable and more susceptible to the effects of weather than glass. Storm windows can increase the efficiency of single pane windows. The single pane window is the least efficient type of glazing. It is only a thin barrier that allows considerable heat loss and gain. Each layer of glass and the air spaces resist heat flow.