A fenestration glazing system composed of more than one layer of glass, with spaces between the layers and sealants to hermetically seal the system. Select this option when it is not possible to determine the exact number of glass layers in the system.
A fenestration system composed of a single layer of glass, with another system, called a "storm window" or "storm panel", composed of one or more layers, on either the inside or the outside of the original single glazed system. Storm panels and storm windows are added to the first fenestration system in order to increase the total insulation value of the combined system, as well as to control infiltration.