Double Hung - Sashes slide up & down and independent of one another. In contrast to a single hung, where only one sash moves (usually the lower).
Casement - Hinges are located on one side that enable sash to pivot outward
Bay Window - Combination of three or more windows where one is parallel to the wall and the others assembled at a 30 or 45 degree angle.
Bow Window - Similar to bay window but in a circular pattern instead of angled.
Slider - Either one or both sashes move by sliding horizontally
Awning – Operates like acasement windows but hinged at top and sash opens from the bottom
Picture – A single, stationary window that is either stand alone or part of a multi-window unit.
U-Value - The most important measure of a window’s performance is its U-value. The U-value indicates the rate of heat flow through a window. The lower the U-value, the more energy efficient the window will be. U-value measures the entire window unit — glass, frame, sash, spacers — and is the only measurement accepted by the U.S. Department of Energy’s EnergyStar program.
R-Value - R-value is the measure of the resistance of glass to the flow of heat. The higher the R-value, the better the glass will be at insulating your home. But R-value is NOT an accepted form of measurement by the National Fenestration Research Council (NFRC) or EnergyStar, as it does not measure the overall window unit.
Solar Heat Gain Co-Efficient - is a measure solar radiation admitted through a window, both directly transmitted and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits.