Presents a numerical simulation model that allows the impact of various design parameters on the thermal performance of windows to be evaluated. The model is for two-dimensional, combined conductive, convective, and radiative heat transfer and determines velocity profiles, temperatures, heat fluxes, and U-factors for the window. The window consists of two glass panes, a space between the glass panels containing a gas, and a sash. The effects of gas type, spacing between the glass panels, a low-emittance coating on one glass pane, sash designs, cladding strips, and between-glass-panels horizontal bar and vertical partition are reported. Comparisons are made to a one-dimensional model. Results from the model provide a more detailed picture of the thermal performance of a window and suggest design options that enhance the thermal performance of a window.

KEYWORDS: models, calculating, windows, heat flow, performance, designing, conduction, convection, solar radiation, analysis, transmittance, double glazing.