• Ameet Bality

A Complete Guide to Low-E Glass




When it comes to windows, the type of glass you select is really important. Approximately 70% of energy loss happens in windows and doors, with 90% of window heat loss occurring through the glass.


In this article, we will explore Low-E insulated glass, focusing on energy efficiency, types of Low-E coatings and helping you decide what is the best option for your project.


What is Low-E Glass?


Low-E, or low-emissivity, glass was developed to reduce the amount of infrared and ultraviolet radiation that enters your home while without reducing the quantity of light that enters. Low-E coatings play an important role in the overall performance of the windows, which can affect the heating, lighting and cooling off your commercial or residential property


How does Low-E Glass Work?

Low-emission glass uses a thin, invisible layer of metal or metal oxide embedded in the glass surface to control heat transfer and insulate windows, reducing energy losses by up to 30-50%. The glass has a gap between the glass layers so that it blocks a large part of the heat radiation from warming glass panes to cooler panes, thereby reducing heat flow through the window. The glass also resists ultraviolet light, preventing sunlight from damaging carpets, curtains, sofas and other furniture.

7 Benefits of Low-E Glass

  1. Soft-coat low E glass has its low-emissivity coating on a surface that is sealed within the unit, which means the coating is less likely to be damaged or scratched, and will likely keep the bulk of its insulating, sun-reflecting, and UV-protecting properties for many years.

  2. Other important qualities, such as better security, noise-proofing, or easy-cleaning technology, are not prohibited by low E glass.

  3. Low E glass is more energy efficient than normal double glazing, potentially saving you money on your heating expenses. It also outperforms ordinary double glazing.

  4. This decrease in heating expenditures equates to a decrease in overall energy use, lowering your carbon footprint.

  5. When compared to conventional uncoated glass, low E glass lowers glare from light sources.

  6. Low-e coatings reduce energy use by maintaining comfortable temperatures inside buildings in cold climates, by reducing the heat load during summer months, and by reducing or eliminating the need for air conditioning.

  7. Low-e coated windows also reduce glare on computer screens and television sets by blocking UV rays from coming in through windows.


Low-E coatings increase living comfort by changing the way glass transfers heat, lowering energy costs over the years. The loss of energy from heating and cooling systems through windows accounts for 4% of the Canadian energy consumption each year, and the Department of Energy has begun to push for better window standards with low-e windows in the forefront. Ultra-thin coatings on low-E glass help to reduce heat transfer through windows, preventing heat from entering the house in a hot climate and escaping in a cold climate.


Where can Low-E be applied?


Low-E coatings can be applied to different surfaces of an insulating glass unit. In a standard double panel are applied four potential surface coatings: the first (1) surface, the second (2) and third (3) surface and the other glass installation (separated by peripheral spacers to create an insulating airspace) and the fourth (4) surface, which is directed inwards. Passive low-E coatings work best on the third and fourth surfaces, which are furthest from the sun, while solar-controlled low-E coatings work best on the second surface. Low-e coatings are considered passive sunscreens because they do not improve performance or value.


Does Low-E Coating look different?

When the Low-E coating is applied, the appearance of the glass does not differ from window to window. At HPG, we use a powerful soft layer of low-E glass containing argon gas in our double-pane glass units topped with warm edge spacers. Remember when we reference a window is low-e, I mean the glass reflects good warmth in the window.

During the manufacturing process, pyrolytic low-e glass contains a thin layer of tin oxide in the glass while it is still hot. The application of tin in each phase welds the glass together, resulting in a permanent coating. Composite glazing is used for single-pane windows and storm doors, but it is not as low-emissive as soft-coated glazing.


Where to find the best options for Low-E Glass?

High Performance Glazing offers a wide variety of coats for passive sun protection that can be applied to clear or tinted glass. Selective low-E coatings have been developed to filter out infrared heat components in the light spectrum. Passive low-e coatings work best on the third or fourth surface closest to the sun, while solar-controlled low-e coatings work best on lite (closest to the sun) and second surfaces.



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