Solar control window film reduces solar heat gain by reflection and absorption. As they also block solar heat gain in winter months, these films are ideal for cooling-dominated climates. Window films can be tinted for solar heat and glare control, but some recent window film options reflect solar heat while maintaining a relatively clear appearance. Window films can have Solar Heat Gain Coefficient (SHGC) and Visible Transmittance (VT) ratings by the National Fenestration Ratings Council (NFRC). The lower a film's SHGC, the less solar heat it transmits. The higher the VT rating, the more visible light is transmitted. To find certified window films, visit the NFRC's Certified Products Directory.
Window film often is applied to the room-side glass surface of windows. Since window film absorbs the portion of solar heat that it does not reflect or transmit, it increases the glass temperature and may cause thermal stress on the glass or insulated glazing seals, particularly on sunny but cold days. Before installing window film, be sure to check whether this interferes with the warranty conditions for your windows and whether self-installation would meet the window film's warranty requirements. Before having window film installed, it is advisable to have a window film professional check your windows' location, type and condition to match the appropriate film to the glass type.