Money might not sprout from branches, but without the right windows, it can undoubtedly escape through the glass!
No one enjoys overpaying to keep their living or working space comfy, whether cranking up the AC in the summer heat or the heat during those chilly winters.
Introducing Low-E glass, short for low-emissivity—a true MVP in insulated glass units (IGUs). Low-E glass teams up with standard glass layers to block unwanted solar heat from entering the summer and keep cozy warmth from fleeing in the winter.
Here’s how it works: Low-e IGUs are stellar at minimizing solar heat gain. This means less unwanted heat during the summer, thanks to a lower solar heat gain coefficient (SHGC)—a fancy term for how much solar heat your windows let in. Come winter, these same Low-e coatings act like a thermal mirror, reflecting your heating inside to avoid energy leaks.
Though Low-e windows might cost a bit more upfront, they cut energy waste by up to 50%. Pair that with double or triple-pane options, and the savings keep stacking up.
Transparent Process: How Low-E IGUs Are Manufactured
Low-e windows are made by first applying one or more ultra-thin coatings to a pane of glass. Each coating consists of a metal element that reflects ultraviolet rays and heat and an outer layer that improves durability.
In creating an IGU with Low-e insulation, a narrow coating strip around the perimeter of a pane’s edge is removed. This directly binds sealants to the glass and prevents coating corrosion.
To maximize efficiency and increase insulation, the space between the panes is filled with an inert gas and sealed. Common inert gasses in IGUs include:
- Argon: is the most commonly used inert gas within IGUs due to its affordability and excellent insulation. It effectively reduces heat transfer through windows, helping maintain a comfortable indoor environment while cutting down on energy bills for heating and cooling.
- Krypton: is more expensive than argon offers superior insulation properties, especially in thinner profiles. Because of its higher density, krypton can provide better thermal performance even in configurations where space is a constraint.
- Xenon: is the priciest of the three but delivers even higher insulation values. Due to its cost, it is less commonly used but can be highly effective in specialized applications where energy savings are a crucial priority.
Choosing Clarity: Types of Low-E Glass for Every IGU
Two Low-E coatings are used in IGUs: pyrolytic hard coat and a soft coat. Both have their strengths and weaknesses in creating energy-efficient windows.
Pyrolytic Hard Coat
While a glass pane is still slightly molten during manufacturing, a single, thin layer of molten metal Low-e coating is applied. As the coating and glass cool, they fuse to form a strong, “hard coat” bond.
This process makes the hard coat more durable but slightly less energy efficient. That’s why a pyrolytic hard coat is often used for exterior windows in harsh weather and strong winds.
Magnetron Sputter Vacuum Deposition
Magnetron Sputter Vacuum Deposition (MSVD), a more energy-efficient solution known as a soft coat, requires more skill during manufacturing.
Once a glass pane is cooled and washed, several Low-E coatings are applied to its surfaces at room temperature in a vacuum-sealed environment immediately before entering an IGU. With its additional coating layers, a soft coat offers more protection from UV rays and solar heat gain. However, it is also more delicate, thus “soft,” and unsuitable for harsher climates.
Some of the highest-performing soft coat Low-e glass is made with a double or triple layer of silver. Silver is incredibly challenging to work with and must be handled by an experienced and certified professional.
Beyond the IGU: Low-E Glass Applications
Low-E glass is practical anywhere energy efficiency is a must. In some cases, state and local codes require it.
Even when not required, Low-E glass is still helpful because it reduces drafts, lowers utility bills, and blocks harmful UV rays while letting in plenty of visible light. It’s an excellent choice for:
- Glass doors: Low-e coatings help maintain a stable indoor environment by minimizing temperature fluctuations and reducing heating and cooling demands.
- Glass walls: Low-e glass ensures that spaces remain comfortably lit and insulated, especially in modern architectural designs, without compromising the aesthetic of expansive, open views.
- Greenhouses: Low-e glass plays a crucial role in optimizing growing conditions. It achieves this by allowing ample sunlight to nourish plants while mitigating the intense heat and harmful UV rays that could otherwise damage delicate crops.
These applications demonstrate how Low-e glass not only aids in meeting energy codes but also delivers tangible benefits in maintaining comfort, protecting interiors, and conserving energy across various structures.
Low-E Glass: FAQs That ShineWhat exactly is Low-E glass, and how does it work? Low-e glass has a special coating that reflects heat. In the summer, it reflects the sun's heat away from your home, keeping it cooler. In the winter, it reflects the heat from inside your home, keeping it warmer. This helps save energy and money on heating and cooling costs. What are the main types of Low-e coatings, and which is right for me? There are two main types: hard coat and soft coat. Hard coat is more durable and better for harsh climates, while soft coat is more energy-efficient but less durable. The best choice depends on your specific needs and climate. Besides windows, where else can Low-e glass be used? Low-E glass can be used in glass doors to maintain a stable indoor temperature and in glass walls to provide insulation and natural light without sacrificing views. It's also used in greenhouses to optimize plant growing conditions. |
Low-e IGUs: An Investment in Savings
Whether you're battling the heat of summer or the chill of winter, Low-E glass tirelessly keeps your space consistently comfortable. It excels at keeping heat and cold exactly where they should be, minimizing energy transfer and maximizing comfort.
Set your thermostat and forget it—season after season.
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(Editor's note: This article was originally published in October 2020 and was recently updated).
