The rate of heat loss through a unit surface area of a window per unit temperature differe...

The rate of heat loss through a unit surface area of a window per unit temperature difference between the indoors and the outdoors is called the U-factor. The value of the U-factor ranges from about 1.25 W/m2∙K (or 0.22 Btu/h∙ft2∙°F) for low-ecoated, argon-filled, quadruple-pane windows to 6.25 W/m2∙K (or 1.1 Btu/h∙ft2∙°F) for a singlc: pane window with aluminum frames. Determine the range for the rate of heat loss through a 1.2-m × 1.8-m window of a house that is maintained at 20°C when the outdoor air temperature is −8°C.