Three panes of glass or plastic with two air spaces between.
Three panes of glass with an air space between each pane.
Use of three panes of glass or plastic with two airspaces between. Generally refers to a sealed insulating unit.
A sash glazed with three lights of glass, enclosing two separate air spaces.
Windows that are made of three panes of glass with air space between the lites, and may be filled with argon or other gases for increased energy efficiency.
Three panes of glass with an airspace between each pane.