Thermal Performance Improvement of Window Drape Configurations

Abstract

Heat transfer through draped windows was studied to identify and test the insulative potential of drapery materials and configurations on a window in a test wall apparatus. Free flow of room air through the window-drape cavity was found to produce dramatic losses in the insulating properties of drapes. Variations of open-bag and wind-screen draping configurations made of conventional drape materials reduced window thermal transmittance values by 50%, a reduction equal to that expected from converting heat transfer from a free convective mode to a conductive mode at the window glass/room air interface. Materials with ideal properties for control of radiative and conductive heat flow were also used as draping elements to quantify the performance levels of the drapes configured to impede natural convection. Simulated drapery materials having radiation barriers configured to minimize air flow were as effective as double pane windows.