The Thermal Transmittance of Windows

The thermal transmission properties of modern windows are recognised to be quite complex and difficult to evaluate by measurements alone. This article from the Federal Institute for Materials Testing (BAM) in Berlin shows how numerical methods by computer programs may be used to calculate the thermal transmittance U and the temperature distribution through a steel-stiffened plastic window and several variations of insulating glazing. The results were in agreement with accepted experimental values, and the authors suggest that the numerical methods should now allow manufacturers to predict heat transmission properties of windows at the design stage.