---
title: "What Is IGU (Insulated Glass Unit)? Window and Door Glossary"
description: "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."
url: https://honeyrock.multisites.ai/glossary/igu
publisher: Honey Rock Window and Door
phone: +1-214-484-9982
quote: https://honeyrock.multisites.ai/contact-us
---

# 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](https://honeyrock.multisites.ai/glossary/low-e-coating), [argon gas fill](https://honeyrock.multisites.ai/glossary/argon-gas-fill), a [warm edge spacer](https://honeyrock.multisites.ai/glossary/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.

[Where it mattersEnergy-efficient windows for Texas](https://honeyrock.multisites.ai/energy-efficient-windows-texas)

## Related terms

-   [Low-E coating](https://honeyrock.multisites.ai/glossary/low-e-coating)
-   [Argon gas fill](https://honeyrock.multisites.ai/glossary/argon-gas-fill)
-   [Warm edge spacer](https://honeyrock.multisites.ai/glossary/warm-edge-spacer)
-   [Laminated glass](https://honeyrock.multisites.ai/glossary/laminated-glass)

## Sources

1.  [Jada Windows: Glazing](https://jada.com/features/glazing)

![A modern home with wide glass doors lit warm at dusk beside a pool](https://honeyrock.multisites.ai/_astro/dusk-modern-home-pool-01.CeePxgPr_Z2giQin.webp)

## Let’s frame your view.

Send your plans or a few photos of the openings. We will help you choose the system, the brand and the glass.

[Start your project](https://honeyrock.multisites.ai/contact-us)[or call (214) 484-9982](tel:+1-214-484-9982)