The objective of this project is to develop a flexible fenestrationsimulation program based on fundamental physicalmodeling of fenestration heat flows that uses an intelligentdefault mechanism with iterative search capabilities toproduce a physically realistic fenestration system based onuser inputs, with the minimum inputs being only the lumpedparameters of U-factor and solar heat gain coefficient(SHGC). As more inputs (e.g., number of panes, gap width,framematerial, etc.) are provided, theprogramwillnarrowthesearch to the remaining unknown properties so that the fenestrationsystem bulk properties and other physical characteristicsof the synthesized fenestration system will matchavailable information from actual fenestration systems. Insome cases, this information may be limited to observablecharacteristics, such as dimensions, number of glass panes,and frame materials. Using such limited input information, thetool generates a detailed physical description of a fenestrationsystem based on real components available on the markettoday. This computer programis designed tobeused inastandalonemode to produce a text file containing information suitableto be input into popular building simulation engines.