How Insulated Glass Units Impact The Energy Efficiency of Modern Windows

Oct 15, 2025

6 min read

211

What Are Insulated Glass Units (IGUs)?

What Window Features Make Insulated Glass Units?

Common Mistakes With Insulated Glass Units To Avoid When Shopping for New Windows

You’ve probably heard them referred to as “sealed units”, “glass seal units” or less commonly by their industry name “insulated glass units.” But in the end the conversation is about the same thing.

Insulated Glass Units (IGUs) is what makes your windows efficient, incorporates additional features, and provides the majority of the value in your replacement.

Read on to know everything about insulated glass and how it impacts the energy efficiency of your replacement windows.

What Are Insulated Glass Units (IGUs)?

An insulated glass unit combines two or three glass panes into a single unit that is joined together by a spacer. The material that used to manufacture the spacer can have a big effect on the energy efficiency of the IGU and the window.

The space between the glass can be filled with air or a noble gas for improved efficiency. Triple-pane windows have two of these chambers and can accommodate more gas. Glass surfaces in insulated glass units can also be utilised for additional features like Low-emissivity coatings.

A cross-section of an insulated glass unit.

What Window Features Make Insulated Glass Units?

Very few additional efficiency features go into the frame of the window. Most of them enhance the performance of the sealed unit, in one way or another. You can click on the links to read more about each feature and how it is beneficial for modern replacement windows.

Insulating Glass Super Spacer

As we mentioned above, the glass panes in an IGU are joined together by a “spacer.” What this spacer is made of has a significant effect on the how well your windows conduct (lose) heat.

At Ecoline, all our windows come with Super Spacer – a state-of-the-art sealing technology that makes your new IGUs more energy efficient and soundproof. Compared to most metal-based spacers, Super Spacer’s all-foam solution blocks heat flow and significantly reduces the condensation. It endures the 140°F temperatures and 95 – 100% humidity.

Argon or Krypton Gas

Combining several panes of glass into one unit results in so-called chambers between the pieces of glass. When windows first became multi-pane these chambers were filled with air. Almost all double and triple-pane windows today utilize a gas fill between the panes.

Both Argon and Krypton gasses are much less reactive than air, and, therefore, don’t transfer energy as quickly. In simple terms, gas fills help your windows keep the warm air inside.

Window Low-E Coatings

When shopping for new windows, you will definitely hear consultants talk about Low-Emissivity coatings. We also often say that if you don’t get any other additional upgrades, low-e is a must for your replacement. And that’s not just a sales gimmick.

A low-e coating works in similar ways to a window film. Except unlike a film, it is actually applied during the manufacturing process and is only several particles deep. Low-emissivity coatings are put on the inner sides of your insulated glass unit, so they can never be scratched or washed away from the outside.

The real reason why most window companies are so committed to selling low-e with their windows is because it serves a purpose both in the winter and summer time. The coating works by deflecting harmful UV rays to prevent overheating the room and fading furniture or paint.

The inner side of the coating helps reflect warmth back into your house reducing heat loss. This is especially important at night time, as during the day your windows gain warmth from the sun and are able to lock it in for as long as possible after the sun goes down.

Replacement Window Internal Grills

Although window grills are considered an aesthetic feature of replacement windows they are still worth mentioning when it comes to the performance of the insulated glass units. In modern windows, grills are put on the inside of the sealed unit. This is important for 2 reasons:

Sealed units with grills are not as efficient as glass units with grills.
If a grill comes undone or falls, the entire sealed unit has to be replaced.

A fallen piece inside the insulated glass unit. This problem is covered by warranty, but usually the whole sealed unit has to be replaced.

Common Mistakes With Insulated Glass Units To Avoid When Shopping for New Windows

We have already discussed the main window features that impact energy-efficiency of your IGUs. In fact, if you feel something is off during your window consultation, be sure to ask any questions concerning insulated glass units and their energy efficiency specs if your consultant doesn’t. Often features like LoE, Argon, and spacer come standard with modern home windows.

But one thing that you absolutely shouldn’t overlook when buying new windows is the warranty terms for the insulated glass units. Because many features come together in a sealed unit and it is the first line of defence against the outside climate, things are more likely to go wrong here than with other parts of the window.

Most companies will warrant their glass units for the same number of years as the window. But very few offer the actual replacement of the glass unit under the warranty. So while you may be able to get a new sealed unit because the grill has fallen inside, you may still have to pay for the re-installation of this sealed unit into your window. Most companies usually offer sealed unit replacement under warranty for a maximum of 5 years.

At Ecoline, we offer 25-year warranty on all products and labour to make sure all your clients have peace of mind and maximum comfort for many years to come.