Some factors that affect window pricing are the number of window panes in the window, the U-factor of the window and the material from which the window frame is made. Further, the type of window frame insulation, window gas and window coating all affect price.
Window panes generally come in either a single, double or triple style. Single-pane windows are typically the least expensive while the three-paned style usually costs the most. However, the double and triple type offer more insulation to the home, which can save money on energy in the long run. The U-factor is the energy-efficiency rating of the window that reveals how well the window keeps hot or cold air within the home. A lower rating signifies better insulation and a generally higher price tag.
When looking at window frame material, know that fiberglass is commonly the most expensive because it's one of the strongest materials used in making frames. Alternatively, wood window frames are usually less expensive but are known to dry out and let cold air in. Window gas, injected between panes to minimize the transfer of air, increases the price of a window. Normally, a window has either no gas, argon or krypton injected into it.