Curtain Wall, also known as the "Nice Clothes" of Architecture | China is the world's largest curtain wall application country, and glass curtain wall accounts for more than 50% of all curtain wall projects. Today, with the continuous improvement of energy-saving standards, Low-E glass is a product that we must pay attention to.

 China Curtain Wall Network invites Qiyun Dongfang Binrong World's Kibing Glass to share with you the 30 most common questions about the selection of energy-saving glass and the application of Low-E glass. Hurry up and save it!

 (1) What are the main types of composite products for architectural glass?

 There are mainly tempered, semi-tempered, interlayer, hollow, coated and their different combinations, such as tempered coated insulating glass, coated laminated insulating glass, etc.

 (2) What is the shading coefficient Sc value?

 The shading coefficient Sc refers to the ratio of the total solar transmittance of the glass to the total solar transmittance of the 3mm standard ordinary transparent glass. The Sc value of the shading system of the glass reflects the heat transfer of solar radiation through the glass, including the heat that is directly irradiated by the sun through the heat and the heat that is radiated to the interior after the glass absorbs heat. A lower Sc value indicates less solar radiation energy passing through the glass.

 (3) Is the shading coefficient Sc high or low?

 Glasses with different shading coefficients are suitable for areas with different climates. The shading coefficient is high, and the solar radiation entering the room through the glass window is more, thereby reducing the heating cost in winter. This glass is suitable for use in northern regions with long winters. The shading coefficient is low, and the blocking effect of direct solar radiation is good, which can reduce the direct solar radiation entering the room. This glass is suitable for use in southern regions with long summers.

 (4) What is the U value of glass?

 The U value reflects the heat energy caused by the glass due to convection and conduction, including the transfer of the glass to absorb the heat energy and then radiate outward. Therefore, the emissivity E of the glass is low, and the U value is correspondingly low. Convective heat transfer energy = U value × (Toutdoor-Tindoor) Toutdoor and Tindoor are the indoor and outdoor temperatures, respectively.

 (5) How many components are there in the total heat energy transmitted through the glass?

 It consists of two parts: direct solar radiation through heat and convection heat transfer. It is expressed as: Qtotal = 630 ×Sc + U×(Toutdoor-Tindoor)

 (6) What are the components of solar radiation?

 It consists of three parts:

 Ultraviolet radiation, wavelength range 0.01 to 0.38 microns.

 Visible light, wavelength range 0.38 ~ 0.78 microns.

 Near-infrared radiation, the wavelength range is 0.78 to 2.5 microns.

 (7) Does the far-infrared thermal radiation come directly from the sun?

 The far-infrared thermal radiation comes indirectly from the sun, and this part of the energy is thermal energy, which is radiated by the sun when it hits the object and is absorbed by the object. Far-infrared thermal radiation generally refers to radiation with a wavelength greater than 2.5 microns. Objects with temperature will emit thermal radiation outward. The higher the temperature, the stronger the thermal radiation emitted, the hotter the human body feels. There are far-infrared thermal radiation indoors and outdoors, but the amount of far-infrared thermal radiation existing indoors and outdoors in different seasons is very different.

 (8) Is there far-infrared thermal radiation indoors?

 Yes, indoor far-infrared heat radiation comes from heating, household appliances, furniture, stoves and human bodies after being irradiated by sunlight, which is the main heat source from indoors in winter.

 (9) How does far-infrared thermal radiation pass through glass?

 Far-infrared thermal radiation cannot be directly transmitted through ordinary glass, but can only be absorbed or reflected by glass. After the glass absorbs this part of the energy, the temperature will rise, and the part of the energy will be dissipated through convection conduction with the air and thermal radiation to both sides. Therefore, this part of the energy eventually passes through the glass, but it is absorbed first and then radiated. way through.

 (10) How to distinguish far and near infrared thermal radiation?

 Near-infrared radiation comes directly from the sun, and its heat sensation is not obvious, but it can be converted into heat after being absorbed by objects. Far-infrared thermal radiation, as a result of solar energy conversion or human production, is itself heat. Looking at the sunlit road in summer, you can see waves of thermal radiation rising from the ground (ie, solar energy is being converted into thermal radiation). Close to the heater in winter, you can directly feel the heat radiation.

 (11) What is offline Low-E glass?

 Off-line Low-E glass is low-emissivity glass, which is formed by coating the glass surface to reduce the emissivity E of the glass from 0.84 to below 0.15.

(12) What are the characteristics of Low-E glass?

 Low-E glass has the following characteristics:

 1. High infrared reflectivity, which can directly reflect far-infrared thermal radiation.

 2. The surface emissivity E is low, and the ability to absorb external energy is small, so that the radiated heat energy is small.

 3. The shading coefficient Sc has a wide range, and the amount of solar energy transmission can be controlled according to needs to meet the needs of different regions.

 (13) Why does the Low-E film reflect heat?

 The Low-E film is coated with a silver layer, which can reflect more than 97% of the far-infrared heat radiation, thus directly reflecting heat like a mirror reflects light. The shading coefficient Sc of Low-E can be from 0.2 to 0.7, so that the direct solar radiation energy entering the room can be adjusted according to the needs.

 (14) What is heat reflective glass?

 Heat reflective glass is commonly known as sunlight control coated glass, which is formed by coating the glass surface to reduce the shading coefficient Sc of the glass from 0.98 (6mm transparent glass) to 0.2 to 0.6.

 (15) Why does Low-E glass save energy?

 The contribution of Low-E glass to energy saving is reflected in two aspects. On the one hand, Low-E film can reduce the heat exchange between the glass surface and the air, and reduce the heat transfer caused by the temperature difference on both sides of the glass (ie, temperature difference heat transfer). , which will reduce the temperature difference heat transfer of the glass; on the other hand, the Low-E film can effectively reflect the solar radiation, thereby limiting the radiant heat energy (ie radiation heat transfer) of the sun shining through the glass, which reduces the solar heat energy passing through the glass. . It is through these two ways that Low-E glass reduces the heat passing through the glass to reflect energy saving. In practical applications, Low-E glass is generally used in structures such as insulating glass and vacuum glass.

(16) What are the mature coated glass processes?

There are two main types: online coating and vacuum magnetron sputtering coating (also called offline coating). "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. Since the coating process is completed on the production line for manufacturing flat glass, Therefore, the low-emissivity glass produced by this technology is called "on-line Low-E glass", and its low-emissivity functional layer is a semiconductor compound. The advantage of the online Low-E film is that the film made on the surface of the 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 disadvantage is that the film thickness control accuracy is poor. It is impossible to make a multi-layer interference film system to selectively control the solar spectrum transmitted through the film layer, and the reflection color of the film layer is single, and the emissivity is high (greater than 0.15).

Another "offline Low-E glass" is manufactured by a vacuum magnetron sputtering coating production line. A thin film is deposited on the surface. When the working gas is argon, the deposited film is the same as the target material. 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 in 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 are that the thickness of the film layer is precisely controlled, and a multilayer optical interference film system can be made to selectively control the solar spectrum transmitted through the film layer, and the reflection color of the film layer is various and adjustable, and the emissivity is low (less than 0.15); The disadvantage is that the hardness of the film layer is poor and it is not resistant to corrosion, so it is also called "soft coating". 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.

(17) Can Low-E glass be used as a single piece?

Except for the online Low-E film and the silver-free Low-E film, the offline Low-E film cannot be used monolithically.

(18) Is the performance of Low-E glass the same?

From a technical point of view, all Low-E glasses handle spectral profiles in the same way, but not all perform the same.

(19) Do all Low-E glass look the same?

Different! Some Low-Es seem to have high transparency, transmittance above 60%, and light color. Some Low-Es seem to have low transparency, transmittance below 45%, and relatively darker colors.

(20) Does Low-E glass still work at night?

 Yes! Low-E glass works day and night. In winter, heat (far-infrared thermal radiation) is reflected back into the room during the day and night, because both the heat generated by heating and the heat converted from solar energy exist in the form of far-infrared thermal radiation.

(21) How does Low-E glass work in summer and winter?

In winter, the indoor temperature is higher than the outdoor, and the far-infrared heat radiation mainly comes from the indoor, and the Low-E glass can reflect it back indoors to keep the indoor heat from escaping. For part of the solar radiation from the outdoors, Low-E glass can still allow it to enter the room, and this part of the energy is absorbed by the indoor objects and then converted into far-infrared heat radiation and left indoors. In summer, the outdoor temperature is higher than the indoor temperature, and the far-infrared heat radiation mainly comes from the outdoor, which can be reflected by the Low-E glass to prevent the heat from entering the room. For solar radiation from outdoor, Low-E glass with low shading factor can be selected to restrict its entry into the room, thereby reducing cooling costs (air conditioning costs).

(22) Which surface of the insulating glass is the most suitable for the Low-E film layer to be located on?

Insulating glass has 4 surfaces, and the numbers from outdoor to indoor are 1#, 2#, 3#, and 4# surfaces respectively. Due to the problem of weather resistance, the offline Low-E film cannot be located on the exposed surface of the insulating glass. It is usually located on the inner surface of the insulating glass gas chamber, namely the 2# or 3#, 1# or 4# surface, but the offline silver-free Low-E film Or the in-line Low-E film can be located on the interior side surface of the insulating glass. Only one glass surface of each gas chamber needs to have a Low-E film. If there is a Low-E film on the other glass of the same gas chamber, its energy saving performance cannot be significantly improved. In the single-cavity insulating glass, the Low-E film can be located on the 2# or 3# side, but it should be noted that this will cause a huge difference in energy saving parameters. When the Low-E film is located on the 3# surface, the shading coefficient Sc is more than 15% higher than that when it is located on the 2# surface, and the effect of blocking sunlight and heat radiation is significantly worse.

(23) What is the function of filling argon in insulating glass?

 Argon is an inert gas, and its heat transfer performance is worse than that of air, so filling it into the insulating glass can reduce the U value of the insulating glass and increase the thermal insulation of the insulating glass. For Low-E insulating glass, argon also has the function of protecting the Low-E film layer.

 (24) What are the negative effects of ultraviolet rays?

 Ultraviolet radiation is short-wave radiation, invisible to the naked eye, and it accounts for about 2% of the total energy radiated by the sun. Ultraviolet rays can kill bacteria, but prolonged exposure can burn human skin and eyes, as well as discolor furniture and clothing.

 (25) How much UV light can be attenuated by Low-E glass?

 Compared with ordinary single-piece transparent glass, Low-E glass can reduce ultraviolet rays by 25%. Low-E glass reduces UV rays by 14% compared to heat reflective coated glass. Low-E glass cannot completely prevent furniture from fading, but it can slow it down.

 (26) What effect does Low-E glass have on indoor plants?

 It has no adverse effect on most common plants, and the effect on special rare plants can be consulted by relevant flower experts.

 (27) Do shades, trees and awnings affect the performance of Low-E glass?

 These objects can limit the heat and light entering the room through the glass window, that is, block part of the solar energy from passing through, but do not affect the performance of Low-E glass.

 (28) Which direction is the best way to install Low-E glass?

 In winter, no matter which direction the Low-E glass faces, it will not affect its function, because it mainly reflects the heat in the room, but the effect of installing it towards the north is the best. There are also some restrictions on solar radiation. In summer, Low-E mainly reflects the outdoor heat, so it is suitable for installation in any direction, but the installation in the east, west and south direction is the best, because it can also reduce the transmission of solar energy.

 (29) How long will the Low-E film last?

 The duration of its coating layer is the same as the duration of the sealing of the insulating glass space layer.

 (30) How many ways are there to combine Low-E glass with tinted glass?

 There are three ways of combining: coating Low-E film on tinted glass, synthesizing insulating glass with tinted glass, and synthesizing laminated glass with tinted glass. Tinted glass further reduces the shading factor of the combined glass product, thereby limiting more direct solar radiation into the interior. Therefore, the combined use of these three methods is very good, and it is more suitable for use in the warm and tropical regions of the south. Combining with tinted glass also greatly increases its decorative effect.