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Low-E Windows

Updated: Jul 19, 2021

Low-emissivity, also known as low-E, coating is a microscopically thin metallic film applied on the glazing that functions like a mirror that radiates heat back into the interior space during the heating season (winter), and back to the exterior environment during the cooling season (summer). This almost invisible metallic oxide layer help minimize heat transfer through windows, thereby reducing energy loss by 30% to 50%.

Low-e coatings gives a double-pane window with almost the same energy performance as a window with uncoated triple-pane window, but at a lesser cost. Most window manufacturers offer low-E coatings as a standard feature in their windows. The low-E coatings are usually installed on multi-pane windows that are filled with argon, an inert, non-toxic, colourless and odourless gas that has higher heat flow resistance than air. In colder, heating-dominated climates such as Manitoba, the low-E coating is applied to the inner layer of the glazing to help keep the heat in. About 40% to 70% the infrared portion of the light spectrum are reflected, while at the same time permits all visible light to pass through.

There are two types of low-E coatings, pyrolytic and sputtered. Pyrolytic coating, also called hard-coat low-E coating, is made of tin oxide and additives installed directly onto the glazing surface during the production process while it’s still hot. This production method results to a hard and sturdy baked-on surface layer on the glazing surface. This type of coating is typically applied on insulated glazing units where the low-E coating is within the sealed air space.

On the other hand, sputtered coatings typically comprise of three primary coatings with at least one layer of metal placed on plastic or glass film. Sputtered coatings must be covered from humidity and contact, which is why they are also commonly called soft-coat low-E coatings. Like pyrolytic coatings, these are usually installed inside the sealed air spaces of multi-pane windows and can be installed in suspended films and to retrofit windows.

Energy-conscious consumers can benefit from understanding the advantages of low-E windows than conventional windows. Selecting windows with low-E coating can significantly reduce energy costs, thereby decreasing our dependence on fossil-fuels.

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