Insulated Glass Unit

What Is an Insulated Glass Unit?

An Insulated Glass Unit (IGU) is a sealed assembly of two or more glass panes separated by a spacer and filled with air or an insulating gas. IGUs significantly reduce heat transfer compared to single-pane glass and are the standard in modern replacement windows.

Construction

A typical dual-pane IGU consists of two glass lites, a spacer (often aluminum or warm-edge material), desiccant to absorb moisture, and a sealant that keeps the unit airtight. Triple-pane units add a third pane and second air space for even better insulation.

Gas Fills

The space between panes is often filled with argon or krypton gas instead of air. These gases are denser and less conductive, improving the unit's U-factor. Argon is the most common; krypton is used in thinner spaces where argon is less effective.

Benefits

IGUs improve energy efficiency, reduce condensation, block more outside noise, and can include low-E coatings for additional performance. They are essential for ENERGY STAR certified windows in the Bay Area.