What Is Low-e Glass?

1. What is Low-Emissivity Glass?

Coatings are thin layers of metal applied to glass to improve solar performance. The first coatings utilized on building facades were reflective coatings which provide a mirror-like appearance and reduce solar heat gain by reflecting the sun’s energy away from the building.

Today, the most popular coatings applied to glass are Low-emissivity (Low-E) coatings. Coatings with low-emissivity properties have low heat transfer properties and offer higher light transmission than traditional reflective coatings.

From the?beginning: the "E" is for emissivity. When heat or?light energy is absorbed by a surface, such as glass, it's either reflected off the surface, or radiated through the surface. A material's ability to radiate energy is known as emissivity.

2. Why do we need to use Low-e Glass?

Low-e coatings in architectural glazing can help?control temperatures inside a building?by providing varying levels of thermal insulation and/or solar control. Low-E glazing can allow plenty of natural light into interior spaces, helping to improve occupant comfort while contributing to the?energy efficiency?of the building.?

Low-e coatings also offer architects a wide range of?aesthetic options?in terms of colors, allowing them to select the most appropriate look to suit their project.

3. How Low-e Glass Works?

The secret to the remarkable insulating qualities of low-e windows is the thin metallic coating on the surface of the glass. Low-e windows often appear tinted, but low-e glass is not the same as tinted glass. Whereas tinted glass is made by adding alloying materials into the glass itself, low-e glass has a microscopically thin layer—often multiple layers—of various metallic particles on the surface. These layers turn the glass into something like a filter, or a sieve. ?

You see, different types of energy have different wavelengths. Infrared, for example, has a long wavelength, while the visible light spectrum has a relatively short wavelength. Different metals will "filter out" different wavelengths, so by adding thin layers of various metals onto the surface of the?glass, it's possible to choose what types of energy get through.?

If you want to filter out long wavelengths (infrared, i.e. heat) while allowing shorter wavelengths (light) to pass right through, low-e glass can do that. Most low-e glass also limits the amount of ultraviolet radiation that is allowed to pass through, which is?beneficial both for the health of those who live in the home, as well as for the longevity of your furnishings. ?

4. How Low-e Glass is Made?

Low-e glass categorized as either "hard coat" or "soft coat." This is another way to differentiate between different types of low-e glass, but it has more to do with how the glass is made. Here's how they're different:?

• Hard coat low-e glass is manufactured trough what is known as a pyrolytic process. With this method, a thin layer of molten metal is applied to a sheet of glass during the manufacturing process, while the glass is still slightly molten. This causes the metal to essentially become welded to the glass, creating a very strong (i.e. "hard") bond.?
• Soft coat low-e glass?is made through a process known as Magnetron Sputter Vacuum Deposition (MSVD). That's a complicated way of saying that with this method, the particles that make up the metal layer are applied to pre-cut sheets of glass, at room temperature. This is done in a vacuum-sealed chamber filled with an electrically-charged inert gas. The resulting metal coating is extremely thin and somewhat delicate (i.e. "soft").?

5. Applications and uses of Low-e glass

The applications for architectural low-e glazing are wide ranging. From windows and curtain walls to roofs and skylights, in fact, any application where glazing is a physical barrier between the inside and outside of a building, low-e glazing can be considered.

• Curtain Walls
• Roofs and skylights?
• Curved glazing
• Oversized glazing

SYP offers a broad selection of both reflective and Low-E coatings. Our coatings can be applied to clear or tinted glass substrates.

In addition, a silk-screen pattern can be applied to the same surface as the coating for excellent solar performance and appearance.

The specific coating needed for a given project is typically dictated by a required solar performance or a desired appearance.

6. Learn More

To learn more about the different types of Low-e Glass, please check with SYP Sales Team directly.