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Low e glass

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Low-E glass

Providing the comfort factor

Low Emissivity (low-E) glass helps keep your interior spaces warm during colder periods. Depending on your needs, it can allow passive heat to assist your heating system during the winter, or in the summer months can help limit the overheating of your interior by limiting the amount of solar energy passing through the glazing. All of this while letting natural light in.

What are the benefits of low-E glass?

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Protect homes from cold and hot weather

Low-E glass helps limit the transfer of heat through the glazing (from the interior to the exterior) and helps maintain the heat inside a home during the colder months. When desired, it can let passive heat in to benefit from the free heat from the sun. Alternatively, in warmer climates or for south-facing windows where the priority is to provide protection from solar energy and prevent your interior from overheating, low-E glass with solar control properties can be used to help limit the solar energy entering a building through the glazing.

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Let the light in

Low-E glass lets a high proportion of the visible light inside. Due to its thermal efficiency, low-E glass can allow larger glazed areas to be created without having to compromise on the thermal comfort of building occupants. Natural light can offer visual comfort and contribute to well-being. Large-glazed areas provide views to the outside and can help connect you to nature and the surrounding environment.

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Improve energy efficiency

Low-E glass can help keep the interior temperature of a home comfortable at all times of the year, while helping to lower the demand on the heating and/or air-conditioning systems, thus contributing to improving the energy efficiency of a building or home.

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Protect the colors of your furniture and floors

Low-E glass helps preserve the color of your interior furniture and floors for longer, as it filters up to 78%* of harmful ultraviolet (UV) rays, which can be responsible for up to 50% of the color fading of materials and fabrics. When combined with laminated glass, it can block up to 99% of damaging UV rays.

*for a triple insulating glass unit with two ClimaGuard Premium2 coated glass

What is low-E glass and how do we use it?

How is low-E glass made?

Low-E glass is a coated glass. Very thin, transparent low-E coatings are applied to the surface of the glass. The process used at Guardian Glass to apply low-E coatings on float glass is the sputter process. This process allows the deposition of multiple layers, resulting in a permanent, nearly-invisible and ultra-thin coating (approx. 1/500th of the thickness of a sheet of paper). Windows with low-E coatings limit the amount of heat that is transmitted through the glass. The coatings are made up of a series of almost invisible layers of various materials and rely on one or more precious metal layers (e.g. silver) to reflect interior heat.

See more in this video how glass is coated:


Insulated Glass Unit (IGU)

Low-E glass must be used in a double or triple insulated glass unit (IGU), and the coating must be positioned inside the IGU cavity. The cavity of the IGU is hermetically sealed and protects the coating from external elements that could deteriorate the coating, which is sensitive to humidity. Low-E coatings are positioned on surface #3 of a double IGU, closer to the interior environment, where the heat can be reflected back into the room. In triple IG Units, low-E coatings are positioned on surfaces #3 and #5, (one coating in each cavity).

See more about how an Insulating Glass Unit works and how to improve its performance.

How is the thermal insulation performance of low-E glass measured?

The U-Value describes the energy transfer caused by an air temperature difference between the inside and the outside of a building. The lower the U-Value, the better the thermal insulation performance of the glazing. For example, using a low-E thermal insulating glass in double glazing can bring the U-Value down to 1.0 W/m2K compared to 2.7 W/m2K for double glazing with standard float glass*. This value can be further improved to 0.5 W/m2K in triple glazing.

*4mm glass - 16mm interspace - 4 mm glass

A solution adapted to the climate and need

Low-E glass products provide thermal insulation, while some also have solar control properties. Depending on the climate, as well as the window orientation and size, the glass option chosen may be different. It is important to take all these elements into consideration to select the glass that will best meet your needs. You can also add additional benefits to your window glass by combining it with laminated glass, for example, to improve sound reduction and/or the safety and security of your windows. We have created a simple tool that can help you understand which glass would be the most appropriate for your windows. You just need to answer a few questions to receive a recommendation.

Our low-E glass product solutions:


Our range of low-E glass products combines light transmission, thermal insulation and sometimes solar control properties, to match virtually every climate and help create more comfortable homes.


Want to know more about glass?

Guardian Glass offers you a wealth of technical notes, tools and online learning to enhance your knowledge about glass and help architects specify the most appropriate glass for your project. Visit our Resource Hub to learn more!


Applications and uses of low-E glass

While the applications for Low-E glazing are wide ranging, it is typically used in residential applications such as homes, apartments, conservatories and orangeries.


Choosing the right glass for windows can improve the looks, performance and energy efficiency of your home. It can also help to enhance your comfort in terms of thermal insulation and solar control.


Choosing the right glass for external doors is important. While the use of glass in doors can provide added light to a home, it can also be a source of heat loss and so choosing a glass with thermal insulation properties can help reduce this. Low-E glass can be combined with laminated glass for added safety and security features.


Conservatories and orangeries

As an extension of your home, a conservatory or orangery should be a place you can enjoy at all times of the year, not just when the sun is shining. Choosing glass with thermal insulation properties, as well as solar control can provide added comfort throughout the year.

Tips to see if you have low-E glass in your windows

You may have recently acquired a home and wonder if you have low-E coated glass in your windows. Or perhaps you have new windows and want to check if the glazing is the one you actually ordered. Hold a source of light close to the window. If it’s double glazing, the image of the light source will be reflected four times. If the glazing contains low-E glass, one of the reflected images will have a different color, while if the IGU contains only standard float glass, the reflected images will all be of the same color.

Some of our eye-catching projects made possible with low-E glass:

Want to see more projects made with Guardian glass? Visit our project section.

Why choose Guardian Glass?

Guardian Glass are experts in the creation and application of glass – constantly developing new glass technologies and techniques to deliver performance glass solutions all around the world. We’re focused on expanding the boundaries of what can be achieved with glass. From landmark architectural projects to home interiors and retail spaces. This means we work hand in hand with our partners and customers across the supply chain to ensure exactly the right outcome. In other words, when it comes to glass, we help you see what’s possible.

Our low-E product solutions

  • ClimaGuard


    ClimaGuard® is a wide range of residential glass products that can be tailored to each home. This could be to suit different climates, aesthetic tastes, privacy concerns, or energy efficiency needs. Whatever the requirement, ClimaGuard® glass can help to offer a solution.

    See more
  • Guardian Sun®

    Guardian Sun®

    Guardian Sun® glass allows you to enjoy natural light and clear views while protecting you from both cold and heat. With an advanced formulation that offers high levels of light transmission, thermal insulation and solar control.

    See more
Still thinking? Answer a few questions about your windows to find out what glass would meet your needs.