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What is “Low E” and how does it work?

“Low E” is short for “low emissivity” and is a thin metallic coating that helps improve the thermal efficiency of windows. There are two main types of Low E coating: hard coat and soft coat.

Hard coat Low E, also known as pyrolytic coating, is sprayed on during the float glass process and is easier to manufacture and handle than soft coat Low E. Hard coat has average performance compared to other products available, but offers high passive solar heat gain (which is desirable in our climate to keep your home warm in winter).

Soft coat Low E, or sputter coating, is produced in a vacuum chamber by applying multiple layers of silver between layers of metal oxide. Soft coat Low E provides the highest performance, with a virtually invisible coating.

Low E primarily targets ways that heat can escape your house in winter, and invade during summer by reflecting radiant heat back toward its source (i.e. the sun in the summer and the warm interior of your home in the winter). This translates to added comfort and energy savings (Cardinal Glass claims that your energy bills can be reduced by 30% by switching to Low E glass).

In a 68° F room, the glass in a single pane window will be 30° F when the outside temperature is 20° F.  The inside pane of glass in an insulated glass unit featuring Cardinal LoĒ³-366 will be 61° in the same situation!

As technology improves, glass manufacturers are producing specific Low E coatings to help you take advantage of local climates. For instance, the south and southwest United States want to minimize solar heat gain, to reduce the amount of energy spent on cooling, while here in the Pacific Northwest, we want to select glass that has a high insulating value (or a low U-Value), while allowing as much passive solar heat gain as possible during the winter. Stop by one of our locations to consult with us to determine the right Low E coating for your project.