INSULATED GLASS UNITS (IGUS)
IGUs are made up of 2 or more panes of glass (varying types and thicknesses are available) held apart by a spacer. The spaces between the glass panes are filled with air or an inert gas and sealed around the edges.
R-value of Glass
The thermal resistance of the total window system (including glass, spacer and joinery type). The higher the R-value, the less heat that is lost through the system and the better the insulation.