Low-e coating function in vacuum glass
The reasons why vacuum glass can reach 0.4W/M2.K ultimate low thermal conductivity,is the contribution of low-E coatings.
As we mentioned before,the main composition of vacuum glass U value is caused by the heat conduction caused by the micro pillars ,and solar radiation,while low-E coatings on glass can reflect the solar radiation significantly.
The component of solar energy
The solar radiation include 3 parts:
- UV radiation- Wavelength range 0.01～0.38 microns: 3% of total solar radiation.
- Visible light -Wavelength range 0.38～0.75 microns：45% of total solar radiation.
- Near infrared radiation-Wavelength range 0.75～3 microns: 49% of total solar radiation.
As UV radiation and visible light can transmit the glass directly and the parameter to measure the capability of glass block these parts is SC (shading coefficient).
Near infrared radiation cannot transmit the glass directly,it can be only been reflected or absorbed by the glass or other objects,after glass absorbing the near infrared radiation,glass temperature,or will increase and become a radiation source itself.Then heat will transmit glass ,the parameter to measure its thermal conductivity is U value.
The function of low-E coating on vacuum glass
Typical float glass emissivity is 0.84.
Low e glass is short for Low emissivity glass,is to have a multi layer coating composing metalic &chemical on glass surface to decrease the glass emissivity ratio from 0.84 to below 0.15,or even only 0.03.
The low emissivity coating can reflect the far infrared radiation directly,especially the silver layer inside the soft coated low-E coating can reflect 98% far infrared radiation like mirrors.
The coating has little capability absorbing the heat,which will control the glass surface temperature very well, the heat re-radiated out from the glass is little accordingly.
Despite controlling the infrared,the coating as a variety options with different visible light transmittance and SC value(0.2-0.7) to control the ratio of direct solar energy transmitted through the glass,which can be selected by users both in hot and cold areas.
The function of low-E coating In vacuum glass,:
- Most far infrared are reflected by the low-E coating.
- The glass temperature is well controlled after absorbing near infrared,the micro support pillars will transmit the heat from the external panel to internal panel.
Low-E coating classifications
There’re 2 kinds of low e glass,soft coated low e coating and hard coated low e coating.
Hard coated low e glass is manufactured on a float glass production line. This type of glass has a single variety, poor heat reflection performance. Its only advantage is that it can be used as monolithic glass or been laminated.
Soft coated low e glass is manufactured by the vacuum magnetron sputtering process .It has a variety of colors, excellent heat reflection performance, and obvious energy-saving characteristics.
Most VIG use soft coated low-E coating that been sealed inside to take the most advantage of the coating.
Soft coated low-E coating can be classified into single silver low-E,double silver low-E and triple silver low-E coating.
|Coating Type||Coating emissivity||Glass Combination||U value-Summer Day||U value-Winter Night||SC||Coating Name|
|Float glass||0.84||5 +0.3V+5||2.44||2.17||0.81|
|Single silver low-E||0.096||5 TLE+0.3V+5||0.79||0.69||0.66||TG PLE88A|
|Double silver low-E||0.034||5 TLE+0.3V+5||0.51||0.47||0.42||TG PDE80A|
|Triple silver low-E||0.033||5 TLE+0.3V+5||0.50||0.465||0.35||JINJING T70|
The main difference between the coatings are:
- Different coating emissivity decide the vacuum glass final U value, lower emissivity,lower U value.
- Double silver/Triple silver low-E has lower SC value based on same light transmittance.
Double silver low-E coating contribute much to vacuum insulating glass thermal performance,while triple silver low-E,for its high processing difficulty and limited further improvement of U value,it’s not suggested to be used in VIG.
Available coatings in HaanGlas vacuum insulating glass
Standard low-E coating used in HaanGlas VIG are S1.16,with up to 80% light transmittance,clearlite visual effect.
Of course not every customers require high light transmittance,HaanGlas offer low-E coatings with different light transmittance to suit the climate and weather.
Beside that,to have variety visual colors, further more coatings and glass combinations are available：
- Body tinted glass + S1.16 / Double silver low-E coating
- Low-E coating on body tinted glass + Clear Glass
- Special color coating -Golden/bronze/Blue color etc.
Further processing of VIG will bring extra safety,and thermal performance of VIG,make it suitable for landmark projects.
HaanGlas is your turnkey vacuum glass manufacturer ,with our unique world class scientists and production technology,HaanGlas will help you save more energy costs in the next decades.