On which side of the glass should the coating layer of Low-E glass be placed

Low-E glass, also known as low emissivity glass, has extremely low surface emissivity and is a film product composed of multiple layers of metals or other compounds coated on the surface of the glass. Its coating layer has the characteristics of high visible light transmission and high reflection of mid to far infrared rays, making it superior in thermal insulation and good transparency compared to ordinary glass and traditional architectural coated glass. When using this type of glass, the coating surface should be placed on one side of the glass chamber to prevent the coating layer of the glass from being eroded by rainwater. As shown in the following figure, taking double-layer insulated glass as an example, the coating layer should be placed inside the cavity of the glass, that is, the second or third surface. Whether the coating surface is placed on the second or third surface depends on the climate conditions in the region:
 

1. Northern cold regions

 

In the north, insulation is the main focus, and the film surface of Low-E glass is generally placed on the third layer. This can reflect the far-infrared radiation of indoor heating back into the room, keeping the room warm, as shown in the following figure;


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2. Southern hot regions

 

In the south, insulation and shading are mainly used. The film surface of Low-E glass is placed on the second layer, which can effectively utilize the strong reflection effect of the glass coating layer on far-infrared rays, block the heat radiation of the outdoor sun, and reduce the indoor temperature rise, as shown in the following figure.


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3. Reference specifications

 

Article 6.2.21 of JGJ103-2018 "Code for Installation and Acceptance of Plastic Doors and Windows":

 

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So far, coated glass has developed to the third generation - three silver Low-E glass, also known as infrared shielding glass. Its significant advantages include:

 

▲ High transmittance: Good natural lighting, saving lighting energy consumption

 

▲ Extremely low total transmittance of solar infrared thermal energy

 

▲ Transparent but not heat permeable, excellent sun shading performance

 

▲ Filter the sun into a cold light source, not too hot when exposed to the west

 

▲ Reduce air conditioning energy consumption and minimize investment in air conditioning equipment

 

▲ Low heat transfer coefficient K value: improving insulation performance

 

▲ Good comfort: The indoor environment is cooler in summer and warmer in winter

 

Let's take a look at the basic structure of Low-E film layer

 

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Based on the number of silver layers contained in the film layer, the excellent performance of List Silver Low_S, Double Silver Low_S, and Triple Silver ow_S will be compared through the following aspects:

 

1. Comparison of Solar Spectral Transmittance Curves of Triple Silver, Double Silver, and Single Silver under Same Transmittance

 

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In the region of solar thermal radiation, single silver has the largest containment area, followed by double silver, and triple silver has the smallest containment area, which means that the heat transmitted through triple silver glass is the least.

 

2. Comparison of photothermal performance parameters of three silver, double silver, and single silver under the same transmittance


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Light to heat ratio (LSG): the ratio of visible light transmittance to total solar transmittance

When the transmittance is the same, the K and Sc values of the three silver Low-E glass are smaller, the photothermal ratio is higher, and it is more energy-efficient

 

3. Comparison of Solar Spectral Transmittance Curves of Triple Silver, Double Silver, and Single Silver under the Same Sunshade Coefficient

 

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When the shading coefficient is the same, the transmittance of three silver is actually higher. While blocking infrared heat energy, it improves the collection of indoor natural light, enhances indoor lighting comfort, and reduces energy consumption. It not only transmits visible light (daylighting), but also blocks infrared radiation (insulation).

 

4. Comparison of photothermal performance parameters of three silver, double silver, and single silver under the same shading coefficient

 

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When Sc is the same, the transmittance of the three silver elements is actually higher, ensuring sufficient lighting while almost blocking all heat, truly achieving transparency without heat leakage!