Window Shades in Energy Conservation

Thermal transmission coefficients of window shadeslwindow systems are measured using a Window Thermal Transmission Apparatus. The thermal transmission coefficients and meteorological data are used to calculate the net energy flow from conduction and solar radiation through shaded and unshaded windows for both heating and cooling seasons for 17 cities. Results for Chicago, St. Louis, and Phoenix are reported in this paper; results for all 17 cities are available (Buchanan and Grasso, 1979). These three cities represent long winters and short summers (Chicago), short winters and long summers (Phoenix), and average length seasons (St. Louis)-three typical seasonal con ditions found in the United States. Energy costs for these three cities are calculated from the net energy flow and 1979 fuel prices, for window systems of 0.32 cm single glass under specified management conditions. These costs represent averages over both win dow orientation and seasonal climatic variations for a particular location. Once the net energy flow is established, then up-to-the-minute computations of the effectiveness of window shade treatments can be made by adjusting to current fuel costs. The findings support that conventional window shades represent a reasonable, economic way for owners of existing homes to reduce heat transfer through windows. The actual savings are dependent upon location, fuel type, and local fuel costs.