Secondary Author(s)

Mills, Laney

Report Number




Windows; Buildings


Windows play an important aesthetic role in our daily lives. At the same time, windows typically add significantly to the cost of heating and cooling buildings. After reviewing the physical principles by which windows add heat to buildings and the standard techniques employed to reduce unwanted heating, this paper focuses on one type of device which is readily available, inexpensive to purchase and operate, and capable of being adjusted to changing conditions on even an hourly basis. The device is the common window shade. This paper develops a simple, but realistic, model for computing the advantage of using reflective interior shades. The quantity of interest for characterizing the performance of a shade is the fraction of incident solar energy that remains in the room as heat. The quantity is called the solar heat gain coefficient (SHGC). It is seen that shades can exert a very significant control over the SHGC.

Date Published



Mills, L., McCluney, R., "The Benefits of Using Window Shades", Reprinted from ASHRAE Journal, November 1993, Vol. 35, No. 11, pp. 20-26. Based on previously published paper "Effect of Interior Shades on Window Solar Gain", by R. McCluney and L. Mills, Proc. ASHRAE Transaction, Vol. 99, Pt. 2, 1993, pp. 565-570


Buildings - Windows



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In Copyright