IGU (Insulated Glass Unit)
An insulated glass unit, or IGU, is two or more glass panes held apart by a spacer and sealed around the edge with an air or gas space between.
The IGU is the glass part of a window or door. A spacer keeps the panes apart. Sealant bonds the stack and keeps moisture out. The sealed space between the panes slows heat flow far better than a single sheet of glass.
What you choose inside the unit sets its performance. Options include a low-E coating, argon gas fill, a warm edge spacer, a third pane, or laminated glass. Each option changes the U-factor and SHGC. Our glass options guide shows how to compare them. Ask for the unit makeup in writing, since two windows that look alike can hold very different glass.
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