With the increasing cost of heating fuels and the recognition of a desirability to conserve energy, the art of insulating homes, and in particular the insulating of existing windows and doors, is receiving continuing and increased attention. A substantial percentage of a home's heat loss is through the glass panes of windows and doors.
Traditional means of insulating against this loss have included the use of heavy and expensive storm windows, the glass of which requires separate frames of wood or aluminum. In addition to the weight, expense and attention associated with windows of this type, they normally interfere with and detract from the beauty of the windows from both the inside and outside.
Another popular means of insulating the window area is the provision of insulating glass which is manufactured in multiple thicknesses of either two or three sheets, each separated by an air space from the other, prior to assembly into the sash. While the insulating capabilities of glazing of this type are far superior to those of a single glass pane, the increased cost of multiple thickness glazing has discouraged its use in many instances. In addition, double glazing has heretobefore been impractical for windows which have an existing single pane, since the sash is not designed to accomodate the increased weight and thickness of the double glazed glass panels.