Manufacturers tell you what you need to know about low-e windows

What are low emissivity (low E or Low-E) windows? What does that mean?

Low-emissivity windows are among the highest rated in Canada, especially when combined with the best window materials. This guide will help you answer your questions about low-e windows, their coatings, and what improves a window’s energy efficiency. So you will know what to look for when choosing ENERGY STAR windows from a window manufacturer.

Here’s everything you need to know about low-emissivity windows, and the importance they place on energy-efficient windows for homes and buildings.

What are low emissivity windows?

The E in low-E windows refers to emissivity, the amount of energy radiated by the glass. Low-emissivity windows have thin layers of metallic coating in or on the glass to reflect heat from the sun and from inside homes without reducing the amount of natural light or affecting the appearance of the windows.

Low E windows are used to keep the sun’s heat out in the summer while keeping it inside your home in the winter. The principle is similar to that applied to thermos. Like a low-E metal-coated glass, a thermos has a silver coating that reflects heat from the food or drink it contains. The design of these windows also gives them insulating properties to maintain the internal temperature.

Why Choose Low E Windows?

How Low-E Windows Help Protect Your Home and Wallet:

Energy saving

When windows are properly installed and designed to be insulating, low-E glazing helps maintain comfortable interior temperatures while helping to reduce the amount of energy required for heating and cooling homes and buildings. Low-E windows can save you up to 50% in energy costs annually.

A filter to block certain wavelengths of light

The sun emits three types of light capable of passing through a window: ultraviolet (UV) light which can damage and discolor interior materials; infrared light (also called thermal energy) that heats a room; and visible light.

The goal of low emissivity windows is to limit the penetration of UV and infrared rays, not visible light.

Although invisible, low-emissivity coatings reflect long infrared (heat), short sunlight, and thermal energy indoors that tries to escape through windows in winter.

How homes lose heat

In an uninsulated house, about 35% of the heat escapes through the walls and 25% through the attic.

The wrong type of window can also be a major cause of heat loss in homes. Windows, doors and floors can cause heat loss of up to 40%. It is estimated that about 70% of energy loss comes from doors and windows, and 90% of heat loss from windows is through glass.

Poorly insulated windows will allow heat to escape in the winter, as will windows that let heat escape from the panes, as is the case with high emissivity glass.

Click to continue to part two!