Window Manufacturers Discuss Everything There is to know about Low-E Windows

What are low-E windows? And what does low-E mean?

Low-E windows are some of the top rated windows in Canada, especially when combined with the best window materials. This guide will help answer your questions about low-E windows and window coatings, along with what makes windows more energy efficient, so you know what to look for when choosing Energy Star windows from your local window manufacturers.

Here’s everything you wanted to know about low-E windows and why they are an important part of energy-efficient windows for homes and buildings.

What Are Low-E Windows?

The E in low-E windows refers to emissivity, which is the amount of energy that is radiated from the window panes. Low-E windows have thin layers of reflective metal coatings in or on the glass to reflect heat from the sun and the interior of homes without reducing the amount of natural light or the appearance of the windows.

Low-E windows help keep the heat from the sun out in the summer while keeping the heat in your home during the winter. Low-E windows work much like a thermos works. Like the low-E metal coating on glass, a thermos has a silver lining that reflects the temperature of the food or beverage it is holding. And like the insulating design of windows, a thermos also has insulating properties to maintain the internal temperature.

Why Choose Low-E Windows?

Low-E windows help protect your home and your wallet. Here’s how:

Energy Efficiency

When combined with proper installation and insulating window designs, low-E windows help maintain comfortable indoor temperatures year-round while helping to reduce the amount of energy required for heating and cooling homes and buildings. Low-E windows can help you save up to 50 percent in energy costs annually.

Filtering Out Certain Wavelengths of Light

The sun emits three types of light that can pass through a window—ultraviolet (UV) light that can damage and fade interior materials; infrared light (also known as heat energy) that will heat a room; and visible light.

The goal of low-E windows is to limit the amount of UV and infrared light that can pass through while still maintaining visible light.

Although invisible, low-E coatings reflect long-wave infrared (heat) energy and short-wave solar energy. Low-E coatings also reflect interior heat energy that tries to escape through windows in the winter.

How Homes Lose Heat

In an uninsulated home, about 35 percent of the heat is lost through the walls, and 25 percent is lost through the attic.

The wrong type of window can also be a major cause of heat loss in homes. Windows, doors, and floors can contribute to 40 percent of a home’s heat loss. While an estimated 70 percent of energy loss occurs through windows and doors, and 90 percent of window heat loss occurs through the glass.

Poorly insulated windows will allow heat to escape in the winter, as will windows with glass that allows heat to radiate from the panes—i.e., glass with high emissivity.

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