ABSTRACT Compared to conventional applied window film, high light-transmitting spectrally selective film cost-effectively blocks unwanted solar energy from entering windows and reduces air conditioning costs without darkening building interiors, impeding the ability to see through existing glass, or changing the external appearance of a building. According to the California Energy Commission, 30 percent of a building's cooling requirements are a function of heat entering through existing glass. Stopping heat at the window is the most effective means of lowering temperatures and reducing HVAC operating costs. In new construction, reducing heat at the window can mean the need for smaller and less-expensive HVAC systems. The solution to overheating through windows is to specify solar control glass or applied window film, though even the best solar control glass performs no better than the best applied window film. Solar control glass can be selected for optimum energy performance in reference to the geograph...