Glass Substrate Affect Low-E Coating Performance
The low-emissivity coating is applied on glass surface to reduce the emissivity and maintain good light transmittance to meet the requirements of natural lighting. At the same time, it limit the penetration of infrared heat radiation, reaching better the thermal insulation performance.
Low-E coated glass is being used as an environmentally-friendly and energy-saving high-performance building material, which is widely used in construction, automobiles. In modern buildings, the energy-saving and ornamental requirements of curtain wall glass are getting higher and higher.
For areas with different climatic conditions, it is particularly important to choose suitable curtain wall glass. Sometimes in order to meet the design requirements, a combination of body tinted glass and Low-E coating is selected. This article will be based on the performance of single silver, double silver and triple silver coating on different glass substrates, and analysis how glass substrate affect coating performance .
Evaluating the heat transferred through the glass consists of two parts, one is the heat energy transmitted through solar radiation, and the other is the heat energy transferred by the environmental temperature difference and long-wave infrared radiation on both sides of the glass.
Usually we use SC-shading coefficient and U value to measure it.
The smaller the Sc, the smaller the solar energy entering the room.
Transfer heat from a high-temperature object to a low-temperature object: heat conduction, heat convection, and thermal radiation.
U value is the heat transfer coefficient, which reflects the heat transfer characteristics of glass and reflects the heat preservation performance of glass. Under the same environmental conditions, the lower the U value, the less heat transfer through the glass, and the better the heat preservation performance of the glass.
Beside that,LSG ( light to solar heat gain) is another parameter showing the glass performance, higher LSG means,under same light transmittance condition, lower solar energy transmitted the glass.
Below tests are based on Ashrae Summer condition:
1.Different glass substrate performance
Whether it’s clear ,low iron or body tinted glass,same glass surface emissivity decide the same U value.
While color darkness decide different SC value,darker glass block more solar energy ,SC value is also lower.
To achieve better energy-saving effects, it is necessary to coat Low-E film on glass, here we calculate performance based on 6 low-E+12A+6 Clear.
2.1 Single silver lowE insulated glass
1.U value basically does not change with the change of the substrate.
2.F green glass has the highest selection coefficient, followed by clear and low iron glass but light transmittance of green glass is nearly 18% lower
3.Based on low light transmittance ford blue and Euro grey glass, coated glass is also the lowest and the lowest LSG,which is not suitable for large area curtain wall.
The same result happened to middle and high light transmittance single silver coatings,see below tables.
2.2 Double silver lowE insulated glass
Let’s analysis double silver low-E again.
1.Apply double silver low-E coating on low iron glass can get the best light transmittance and the best LSG.
2.Insulated glass U value won’t affected by the glass substrate.
3.Compared with single silver low-E,double one has better LSG.But applied on low light transmittance body tinted glass,SC won’t decrease significantly which will lose its energy advantage.
Different LSG of single silver low-E coating on different substrate
Triple silver low-E coatings has the same conclusion.
Applied with same low-E coatings,different substrate will have different light and heat characteristics.
Low iron glass exhibits higher transmittance and selectivity in double silver and triple silver coatings, as well as excellent energy-saving properties.
Although green glass has higher LSG in some IGU systems, its visible light transmittance is lower. However, dark color body tinted are not suitable for large-area curtain walls due to their low transmittance.
In practical applications, we found that the curtain wall using ultra-white glass not only has excellent energy-saving properties, but also has a good appearance effect. If no special requirements for tglass curtain wall colors t,it’s suggested to use glass combination of low iron glass with Low-E coatings to have better energy-saving characteristics and ideal appearance.
In Southeast Asian and Middle East countries,customers prefer using glass combination of grey glass and low-E coatings,even though overall light transmittance can be controlled below 25%,but solar coefficient is not good as expected.
We not only manufacture high end double ,triple silver low-E but also coating on different substrates-clear,low iron,grey,blue,green,bronze etc to achieve your every glass requirement,kindly contact us for your next great building.
Learn about the body tinted low-E Glass price :Low-E coating on tinted glass IGU price
Apply this article :Glass substrate affect low-E coating performance
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