90.1-2019
This data structure describes the frame, glass, air gap and other components of a window or skylight. Information may be defined in multiple ways, but the criteria themselves are published as a combination of U-factor, solar heat gain coefficient (SHGC), and visible light transmission (VT) for the installed fenestration assembly. Some simulation programs use more detailed methods of describing the performance of fenestration that take into account the angle of incidence of sun striking the fenestration and other factors, such as the properties of each pane and the fill. Some simulation programs only use whole window performance properties (U-factor, SHGC, VT).