What is low e glass and how does it work?

What is low e glass?

Low e is the shortened term for low emissivity. Emissivity of a surface refers to the amount of energy it emits at specific wavelengths. This is directly affected by the amount of long-wave infrared energy it absorbs, as the more energy absorbed the more the surface emits.

A significant amount of heat in a home can be lost through the windows and doors. This is due to the fact that glass has a high emissivity rate, meaning it absorbs heat and then transfers it from the inside of the property to outside and vice versa.

Low e glass has a thin coating applied to the internal side of both the inner and outer panes in a double or triple glazed unit. This coating reflects the long wave heat energy that the glass would normally absorb, lowering the emissivity of the panes and helping to keep a home well insulted.

Sieger uses a low e coating on all double and triple glazed products to ensure our customers have the best glazing solutions.

refurbished and renovated home with glazing from sieger

How does it work?

A low e coating stops the glass from absorbing heat energy and reflects it out. This means that any heat within a home cannot escape and will be reflected back into the internal living spaces.

By reflecting the waves back into the home, this helps to maintain a high energy efficiency whilst keeping heating bills low.

This also means that heat from the external areas don’t enter the internal areas. An advantage of this is that it prevents a hot climate from overheating the inside of the property and aids in controlling solar gain.

Emissivity is rated on a scale from 0 to 1, with 0 being a low emissivity rate meaning the material reflects all heat energy and 1 being high emissivity meaning it absorbs all heat energy and therefore is not thermally efficient.

Naturally, glass has a relatively high emissivity rate but using a low e coating on the glazing can greatly reduce this. The average standard clear glass pane can have an emissivity rating of up to 0.9, and low e coatings can reduce this to below 0.1.

sieger aluminium casement window with grey frames
how a low e coating works diagram

Advantages and Disadvantages

Another advantage of low e glass is that it can provide a certain level of UV protection as the coating applied to the glass will block UV and infrared light.

This is important as UV light can fade furniture and flooring within a property. So this coating can help to prevent this and preserve your interior design features.

Low e coatings can also be used in conjunction with other glazing features such as glass coatings and decorative interlayers.

Some glass coatings can have the slight disadvantage of causing the glass to have a minor coloured tint. Low e coatings are a microscopic transparent layer and the difference is barely noticeable to the naked eye.

The only disadvantage of low e coatings is that it can be more expensive. Some glazing companies will charge extra for low e coatings on glass which can deter some people.

Sieger uses these coatings on all external glazing solutions, therefore this is not an issue and our customers benefit from the many advantage of low e glass.


For more information contact our technical team who will be able to answer any questions and discuss your project in more detail.

To talk to the team, call 01494 722 882 or email [email protected].

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