- October 4, 2021
- Glass and Mirror Products Info
Eliterglass Double Glazed Low-E Insulated Glass Products Configuration
Glass Selection
1. Types of glass
(1) Clear Float glass
High transmittance, low reflectivity, and poor shading performance. The single-layer transparent glass has poor heat insulation performance, and the transparent insulating glass forms an intermediate air layer that does not produce convection, so the heat transfer coefficient is significantly reduced.
Therefore, the most important measure to improve the insulation performance of doors and windows is to use hollow glass, but the shading coefficient of transparent hollow glass is not improved much.
(2) Tinted glass
The visible light transmittance and shading coefficient of glass is reduced, and the heat transfer coefficient is the same as that of transparent glass.
(3) Sunlight control coated glass
It has a certain control effect on sunlight, the shading coefficient is reduced, and the heat insulation performance is improved, but it has no obvious reflection effect on far-infrared heat radiation.
The heat transfer coefficient is similar to that of transparent glass, but the coated glass with high visible light reflectivity is prone to light pollution.
(4) Low-E glass
It is a kind of coated glass with high reflectance to far-infrared. Since the heat transfer caused by temperature difference is mainly concentrated in the far-infrared band, Low-E glass has a very low heat transfer coefficient, high infrared reflectivity, and low surface emissivity.
Visible light transmittance is moderate, the range of shading coefficient is wide, and it can be selected according to needs, and so on.
Emissivity of glass
The emissivity E value of the glass surface is a standard for judging whether it is Low-E glass and an important indicator of energy-saving characteristics.
It directly affects the heat transfer coefficient of the glass. The lower the emissivity, the smaller the heat transfer coefficient.
The emissivity of transparent glass is about 0.83,
The emissivity of online Low-E glass is lower than 0.25,
The emissivity of offline Low-E glass is lower than 0.15, and the heat transfer coefficient of Low-E insulating glass varies with the emissivity of the Low-E film.
Low-E glass coating surface position
Since the Low-E glass film surface has low radiation properties, it plays an important role in reducing the K value.
The monolithic glass film should be indoors.
The hollow glass membrane must be placed on the inner surface of the glass.
Insulating glass Low-E film is in different positions, and its optical properties are different.
The 4 surfaces of the hollow glass are No. 1, No. 2, No. 3, and No. 4 from the outside to the inside. The test results show that the same original glass (6 mm + 12A + 6 mm) is combined with hollow Low-E glass.
When Low-E film is located on No. 2 and No. 3 surfaces, the hollow glass has the same visible light transmittance of 0.71 and K value of 1.8 W / (m2·K), and the K value is the smallest. The Low-E film on the 2nd side (shading coefficient 0.68) has a lower shading coefficient than on the 3rd side (shading coefficient 0.76),
So the Low-E film surface should be on the 3rd side in severe cold areas; the Low-E film surface should be It’s on the 2nd side.
Thickness of glass
The heat transfer coefficient of insulating glass is related to the thermal conductivity of the glass and the thickness of the glass.
When the thickness of the glass increases, it will increase the thermal resistance of the glass and reduce the heat transfer coefficient, but it has little effect on reducing the K value of the glass.
Low-E insulating glass (8mm+12A + 8 mm) has a lower heat transfer coefficient than Low-E insulating glass (6mm+12A+6mm) by 0.01 W / (m2·K).
Therefore, increasing the glass thickness has little effect on reducing the heat transfer coefficient of insulating glass, and has little effect on building energy consumption.
The thickness of the spacer gas layer
The thickness of the insulating glass spacer gas layer is 6 mm, 9 mm, 12 mm, etc.
The thickness of the spacer layer affects the size of the heat transfer resistance.
The larger the spacer layer, the greater the heat transfer resistance and the lower the K value.
For example, the low-E outer piece of hollow glass (6 mm + 12A + 6 mm), the K value is about 1.8 W / (m2·K) when the spacer layer is 12 mm, and the K value is about 2.1 W when the spacer layer is 9 mm. / (m2·K).
When the spacer layer is 6 mm, the K value is about 2.6 W / (m2·K), but when the gas spacer layer is increased to a certain extent, the gas will form convection under the action of the temperature difference between the glass, which reduces To increase the thickness of the gas layer,
Therefore, the reasonable thickness of the insulating glass layer is 12 mm, which can reduce the heat transfer coefficient and convection heat transfer.
Type of spacer gas
Due to the effect of the gas spacer layer, the thermal conductivity of hollow glass is lower than that of monolithic glass. In addition to air, there are inert gases such as argon.
Due to the low thermal conductivity of the inert gas, improving the thermal resistance performance reduces the K value.
For example, the hollow glass (6 mm + 12A + 6 mm) outer sheet Low-E, when filled with air, the K value is about 1.8 W / (m2·K), when filled with argon, the K value is about 1.5 W / (m2· K).
However, no matter what kind of spacer gas is selected, the same glass type and the same thickness of the gas spacer have no effect on the visible light transmittance of the insulating glass, and it has little effect on the shading coefficient.
At last, the energy consumption of exterior windows of buildings accounts for more than 50% of the total energy consumption of buildings. On the way to green buildings, energy-saving doors and windows must be the key to reaching the goal.
I believe everyone knows the great influence of glass on the thermal insulation performance of the entire window.
How to improve the thermal performance of the glass part, how to choose the most cost-effective configuration, contact us Eliterglass.
Category: Double glazing insulated glass