No one wants to spend more money than they have to in keeping a space’s temperature comfortable.
That’s where low-e -- or low-emissivity -- glass comes in.
Pairing the performance of standard glass sheets with energy efficiency, insulated glass units (IGU) with low-e glass are designed to be a barrier from sunlight and cold drafts.
With enhanced insulating properties against the elements, low-e glass IGUs reduce your heating and cooling costs.
What is Low-E Glass and How Are Low-E Glass IGUs Manufactured?
Low-e glass is made by applying one or more ultra-thin coatings to a pane of glass. Each coating consists of an element that reflects ultraviolet rays and heat, as well as an outer layer that improves durability.
In creating a low-e IGU, a narrow strip of coating around the perimeter of a pane’s edge is removed. This allows sealants to directly bond to a piece of glass and prevents coating corrosion.
To maximize efficiency and increase insulation, the space between panes is filled with inert gas and sealed. Common inert gasses in IGUs include:
Argon is most often used in low-e glass IGUs, as it’s the most affordable.
What Types of Low-E Glass Are Available for IGUs?
There are two types of low-e glass used in IGUs: pyrolytic hard coat and soft coat.
During manufacturing, a single layer of low-e coating is applied to a pane of what will become pyrolytic hard coat low-e glass. As the coating and glass cool, they fuse. This process makes the low-e coating more durable, but slightly less energy efficient. That’s why pyrolytic hard coat low-e glass is used for exterior windows in environments where harsh weather and strong winds are common.
A more efficient product, soft coat low-e glass requires a bit more skill during manufacturing. Once a glass pane is cooled and washed, several low-e coatings are applied to its surfaces immediately before going into an IGU. With its additional layers of coating, soft coat low-e glass offers more protection from UV rays and solar heat gain.
Some of the highest-performing soft coat low-e glass is made with a double or triple layer of silver. Of note, silver is especially challenging to work with and must be handled by an experienced and certified professional.
Beyond the IGU: Low-E Glass Applications
Anywhere energy efficiency is a must, low-e glass is practical. In some cases, state and/or local codes require low-e glass.
Even when not required, low-e glass is still helpful because it reduces drafts, lowers utility bills, and blocks harmful UV rays. All the while, low-e glass still lets in plenty of visible natural light.
Low-e glass is excellent for:
- Glass doors
- Glass windows
- Glass walls
Low-e Glass IGUs: An Investment in Savings
Regardless of climate, low-e glass IGUs help you maintain a consistent temperature in just about any space. In other words, low-e glass keeps both the cold and heat where it belongs -- outside.
Your thermostat can remain relatively untouched, no matter the season.
Interested in using low-e glass IGUs to reduce utility bills?
Editor's note: This article was originally published in October 2020 and was recently updated).