Windows provide natural light and ventilation and are classified by the method by which they open and close (e.g. double-hung window). Windows are made from wood, steel, aluminum, vinyl, vinyl-clad wood or aluminum. Some modern windows have a thermal break, usually Bakelite, between the interior and exterior part of the window to prevent condensation during the winter months.
Pane (or glazing): the plate of glass (usually 1/8 inch thick for single pane.)
Sash: the portion of the window that slides or pivots when you open and close the window unit. The sash includes the glass, its supporting framework, locks and lifts.
Rails: top and bottom part of the sash.
Stiles: sides of the sash.
Stops: hold the sashes in place when sliding or stops a closing window that pivots.
Jamb: the side of the window frame.
Sill: the bottom of the window frame.
Head: the top of the window frame.
Muntins or Mullions: used to divide the pane into several sections (not shown).
Casing or Trim: the decorative material (usually wood) that covers from the edge of the window frame to the finished wall (not shown).
Most insulated glass units are double or triple-pane windows that are sealed with an epoxy to create an air gap between each plate of glass. The window frame is perforated on the inside and filled with a desiccant material that absorbs the moisture vapors from between the glass plates. The wider the dry air space, the greater the insulating value of the unit. Manufacturers also use a coating over the glass for greater energy efficiency. The coating is often called low-emissivity or low E glass. Low E glass reflects radiant heat in the summer and retains interior heat in the winter. Very few manufacturers hermetically seal or create a dry air gap between the panes and then use an air tight seal. Anderson Windows switched from hermetically sealing the window to using the epoxy and desiccant method.
The double-paned window uses 1/8 inch or 3/16 inch glass separated by a 1/2-inch, 3/4-inch or 1-inch air space. A double-paned window is different from an insulated glass unit, because the glass panes are not sealed to create an insulated air space. Consequently, the panes can be replaced without replacing the entire sash.