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Low-E Glass

Low-E glass is made by coating a film with low emissivity on the glass surface by physical or chemical methods, referred to as low-emissivity glass, and English as Low Emissivity Coating, so it is also called Low-E glass. At present, the mature technology of commercial production of Low-E coated glass includes vacuum magnetron sputtering process (physical method) and chemical vapor spraying process (chemical method).

What is online Low-E glass (hard coated Low E glass)?

Online Low-E glass is a Low-E film plated by chemical vapor spraying technology in the high temperature area of glass forming on the production line for manufacturing float glass. Because the film process is completed on the production line for manufacturing flat glass Therefore, the low-e glass produced by this technology is called “on-line Low-E glass”, and its low-e functional layer is a semiconductor compound.  its disadvantages are: 

The advantages of online Low-E glass:

the film made on the surface of high temperature glass is firmly bonded to the glass and resistant to scratches, so it is also called “hard coating” and can be used in a single piece.

The disadvantages of online Low-E glass:

Poor control accuracy of film thickness

It is impossible to make a multi-layer interference film system to selectively control the solar spectrum transmitted through the film layer

The reflection color of the film layer is single

The emissivity is high (more than 0.15).

What is offline Low-E glass (soft coated Low E glass)?

Offline Low-E glass is manufactured by vacuum magnetic digging sputtering mirror film production line. When the working gas is argon, the deposited film is the same as the target material, and when the working gas is oxygen, nitrogen and other active gases, the deposited film is the compound formed by the reaction between the target material and the gas. The general coated glass production line is equipped with a number of different targets, which can continuously coat independent film layers of different materials and stack them into a multi-layer composite film. Since the coating process is completed on an independent coated glass production line, it is called “offline Low-E glass”, and the low-e functional layer is a metallic silver layer. 

The advantages of offline Low-E glass:

1. The thickness of the film layer is precisely controlled, a multi-layer optical interference film system can be made to selectively control the solar spectrum passing through the film layer.

2. The reflection color of the film layer is various and adjustable.

3. The emissivity is low (less than 0.15); 

The disadvantage of offline Low-E glass:

1. The hardness of the film layer is poor and it is not resistant to corrosion, so it is also called “soft coating”.

2. It should be noted that the offline silver-free Low-E film produced by the latest technology has the characteristics of wear resistance and corrosion resistance, so the film layer can be used indoors, referred to as silver-free Low-E film, indoor Low-E film.

How long does offline Low-E stay effective?

Based on the consideration of energy saving effect, all Low-E glass is basically used as insulating glass, and the Low-E film is located inside the hollow glass cavity, so the problem about the life of the Low-E film layer is converted to Low-E The problem of insulating glass life. Because the dryness of the gas cavity inside the qualified insulating glass is very high, the dew point is below -40°C, that is, the water vapor is scarce until the temperature of the inner surface of the glass is lower than -40°C. The E film is stable, so it can be said that the sealing duration of the Low-E film layer and the insulating glass gas cavity is the same, which is simply the same as that of the insulating glass. This conclusion has been confirmed by decades of practical experience at home and abroad. Cases such as discoloration and corrosion of the Low-E insulating glass film in actual use are all caused by the failure of the insulating glass seal and the infiltration of water vapor.

What are the characteristics of Low-E glass?

(1) The heat transfer coefficient K value is low, and the ability to resist temperature difference heat transfer is strong, which is beneficial to energy saving in winter and summer;
(2) The shading coefficient SC has a wide range, which can meet the needs of shading in different regions;
(3) Good comfort performance, which can prevent sun exposure and balance indoor temperature;
(4) Except for the online Low-E film and the silver-free Low-E film, the offline Low-E film cannot be used monolithically.

What kind of coated glass can be considered as Low-E glass?

In physics, all objects with an emissivity lower than 0.15 are classified as low-emission objects, so it seems that the emissivity of Low-E glass should be lower than 0.15. In fact, the emissivity of offline Low-E glass is lower than 0.15. Silver and triple silver Low-E glass even as low as 0.03. However, the emissivity of online Low-E glass is higher than 0.15, about 0.18~0.22. Strictly speaking, it is not a low-emission object, so it is also called K glass abroad, although the emissivity of online Low-E glass is still It is much lower than 0.84 of ordinary glass, so it is also included in the low-emissivity glass series and called “online Low-E glass”.

How does Low-E glass work in summer?

In summer, the outdoor temperature is higher than the indoor temperature, and the far-infrared radiation generated by the environment mainly comes from the outdoor, which can be reflected by the Low-E glass to prevent the heat from entering the room. For the direct solar radiation from the outdoors, the shading type Low-E glass can reflect most of it, thereby reducing the cooling cost of the air conditioner.

How does Low-E glass work in winter?

In winter, the indoor temperature is higher than the outdoor, and the far-infrared radiation mainly comes from indoors. Low-E glass can reflect it back indoors and keep the heat from leaking. For outdoor solar radiation, traditional Low-E glass can allow a large amount of it to enter the room. This part of the heat is absorbed by indoor objects and then converted into far-infrared radiation to be kept indoors, thereby saving heating costs.

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