The purpose of this document is to guide the design, fabrication, and use of multiple-cavity Insulating Glass (IG) within the fenestration industry. As such, this document is not intended to duplicate pre-existing guidelines for single-cavity IG. Rather, it is meant to expand upon those guidelines where requirements for multiple-cavity IG differ from those of single cavity IG. These guidelines have been developed from the collective experiences of insulating glass manufacturers, glass and glazing material suppliers, design engineers, industry consultants and persons experienced in successful IG manufacturing. By this nature, they reflect existing technology and are subject to periodic review and change.