Those who are engaged in curtain walls must understand glass, especially low-e glass. Today, I have sorted out 30
common questions about low-e glass for everyone. Hurry up and collect them!
1 What are the main types of composite products for glass?
There are mainly tempered, semi-tempered, sandwich, hollow, coated, and their different combinations. For example, tempered coated insulating glass, coated laminated insulating glass, etc.
2 What is the shading coefficient Sc, and which part of the heat transfer does it reflect?
Shading coefficient Sc: Under the same conditions, the ratio of the solar radiant energy through the glass to the solar radiant energy through the 3mm transparent glass. The solar radiation energy through 3mm transparent glass is 630w/m2.
Shading coefficient Sc = direct solar radiant energy ÷ 630 w/m2
Direct solar radiant energy = 630 w/m2×Sc The shading coefficient reflects
the heat transfer of direct solar radiation through the glass.
3 Is the shading coefficient Sc high, or low?
Glass with different shading coefficients is suitable for areas with different climates. The shading coefficient is high, and the solar radiation entering the room through the glass window is large, thereby reducing the heating cost in winter. This kind of glass is suitable for use in northern regions where the winter is long. The shading coefficient is low, and the blocking effect of direct solar radiation is good, which can reduce the direct solar radiation energy entering the room. This kind of glass is suitable for use in southern regions where the summer is long.
4 What is the U value? Which part of the heat transfer does it reflect?
The U value reflects the heat energy transmitted through the glass due to convection and conduction, including the transmission of heat energy that the glass absorbs and then radiates outward. Therefore, the emissivity E of glass is low, and the U value is correspondingly low. Convective conduction heat energy = U value × (T outdoor-T indoor) T outdoor and T indoor are
the indoor and outdoor temperatures respectively.
5 How many parts of the total heat energy transferred through the glass are made up? How to express?
It consists of two parts: direct solar radiation heat transfer and convection conduction heat transfer. Expressed by the formula: Q total = 630 × Sc + U × (T outdoor-T indoor)
6 What are the components of solar radiation?
It consists of three parts: ultraviolet radiation, with a wavelength range of 0.01 to 0.38 microns. The visible light wavelength range is 0.38～0.75 microns. Near-infrared radiation,the wavelength range is 0.75 to 3 microns.
7 Does far-infrared heat radiation come directly from the sun?
Far-infrared thermal radiation comes from the sun indirectly. This part of the energy is heat energy, which is radiated by the sun after it hits the object and is absorbed by the object. Its wavelength ranges from 3 to 40 microns. In summer,the far-infrared heat radiation emitted by outdoor roads and buildings under sunlight is one of the main heat sources from outdoors.
8 Is there far-infrared heat radiation indoors?
Yes, indoor far-infrared heat radiation comes from heating, household appliances, furniture, stoves and human bodies irradiated by sunlight. It is the main indoor heat source in winter.
9 How does far-infrared heat radiation pass through the glass?
Far-infrared heat radiation cannot be directly transmitted through ordinary glass, but can only be absorbed or reflected by the glass. After the glass absorbs this part of the energy, the temperature will rise, and it will lose this part of energy through convection conduction with the air and heat radiation to both sides, so this part of the energy eventually passes through the glass, but it is absorbed and then radiated Way through.
10 How to distinguish far-infrared thermal radiation and near-infrared radiation?
Near-infrared radiation comes directly from the sun, and its heat is not obvious, but it can be converted into heat after being absorbed by an object. Far-infrared heat radiation, as a result of solar energy conversion or artificial production, is itself heat. Observing the road under sunlight in summer, you can see thermal radiation waves rising from the ground (that is, solar energy is being converted into thermal radiation). Near the heater in winter, you can directly feel the heat radiation.
11 What is Low-E glass?
Low-E glass is low-e glass, which is formed by coating the glass surface to reduce the emissivity E of the glass from 0.84 to less than 0.15.
12 What are the characteristics of Low-E glass?
Low-E glass has the following characteristics:
★ High infrared reflectivity, can directly reflect far-infrared heat radiation.
★ Thesurface emissivity E is low, and the ability to absorb external energy is small, so that the re-radiated heat energy is less.
★ The shading coefficient Sc has a wide range, and the amount of solar energy can be controlled according to the needs to meet the needs of different regions.
13 Why does Low-E film reflect heat?
The Low-E film is plated with a silver layer. The silver can reflect more than 98% of the far-infrared heat radiation, thus directly reflecting the heat like a mirror reflecting light. The shading coefficient Sc of Low-E can be from 0.2 to 0.7, so that the direct solar radiant energy entering the room can be regulated as needed.
14 What is heat reflective glass?
Heat-reflective glass is commonly referred to as 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 0.2-0.6.
15 What is the functional difference between Low-E glass and heat-reflective glass?
Heat-reflective glass reduces the shading coefficient of the glass and restricts the direct solar radiation from entering the room through the glass, thereby achieving the purpose of reducing air-conditioning costs and saving energy. Low-E glass reduces the U value of the glass to restrict the far-infrared heat radiation from penetrating the glass, so as to achieve the purpose of reducing the convective conduction heat energy penetrating the glass. At the same time, the shading coefficient Sc of Low-E glass has a large adjustment range, which can effectively control the direct solar radiation energy entering the room.
16 What are the main mature coating glass processes?
There are two main types: online coating and vacuum magnetron sputtering coating (also called offline coating). In-line coated glass is manufactured on a float glass production line. This type of glass has a single variety, poor heat reflection performance and low manufacturing cost. Its only advantage is that it can be hot-bent. The coated glass manufactured by the vacuum magnetron sputtering process has a variety of varieties, excellent heat reflection performance, and obvious energy-saving characteristics. The disadvantage is that it cannot be hot-bent.
17 Can Low-E glass be used as a single piece?
The Low-E glass manufactured by the vacuum magnetron sputtering process cannot be used in a single piece, but can only be used for synthesis of insulating glass or laminated glass. But its emissivity E is much lower than 0.15, and can be as low as 0.1 or less. The Low-E glass manufactured by the online coating process can be used in a single piece, but its emissivity E=0.28, strictly speaking, it can no longer be called Low-E glass (in science, objects with emissivity E £ 0.15 are called low-emissivity object). Low-E glass is most effective in a similar closed space formed in sealed insulating glass,because this closed space eliminates air flow on the Low-E surface, so that the Low-E glass can perform better.
18 Is the performance of Low-E glass the same?
From a technical point of view, all Low-E glass processes the spectral curve in the same way, but the performance is not all the same.
19 Do all Low-E glasses look the same?
Different! Some Low-E seems to be highly transparent, with a transmittance of more than 60%, and the color is light. Some Low-E seems to have low transparency, transmittance is below 55%, and the color is relatively darker.
20 Does Low-E glass still work at night?
Yes! Low-E glass works day and night. In winter, heat (far-infrared heat radiation) is reflected back indoors during the day and night, because the heat generated by heating or converted from solar energy is in the form of far-infrared heat radiation.
21 How does Low-E glass work in summer and winter?
In winter, the indoor temperature is higher than outdoors, and the far-infrared heat radiation mainly comes from indoors. Low-E glass can reflect it back indoors to keep the indoor heat from escaping. Low-E glass can still allow part of the solar radiation from the outside to enter the room. This part of the energy is absorbed by indoor objects and then converted into far-infrared heat radiation and left indoors. In summer, the outdoor temperature is higher than indoors, and the far-infrared heat radiation mainly comes from the outdoors. Low-E glass can reflect it out to prevent heat from entering the room. For outdoor solar radiation, Low-E glass with low shading coefficient 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?
Insulating glass has 4 surfaces, the number from outdoor to indoor is 1#, 2#, 3#, 4# surface. Areas where heating demand exceeds cooling demand (northern area), Low-E film level surface. Conversely, in areas where cooling demand exceeds heating demand (southern areas), the Low-E film should be located on the 2nd surface.
23 What is the role of argon filling in insulating glass?
Argon is an inert gas, and its heat transfer performance is worse than that of air. Therefore, filling the hollow glass can reduce the U value of the hollow glass and increase the heat insulation of the hollow glass. For Low-E hollow glass Glass and argon also protect the Low-E film.
24 What are the negative effects of ultraviolet light?
Ultraviolet is short-wave radiation, invisible to the naked eye, it accounts for about 2% of the total energy of solar radiation. Ultraviolet rays can kill bacteria, but long-term exposure can burn human skin and eyes.
It will also fade furniture and clothing.
25 How much ultraviolet light can Low-E glass attenuate?
Compared with ordinary single-piece transparent glass, Low-E glass can reduce ultraviolet rays by 25%. Compared with heat-reflective coated glass, Low-E glass can reduce ultraviolet rays by 14%. Low-E glass cannot be finished .Avoid furniture fading, but it can slow down the fading.
26 What effect does Low-E glass have on indoor plants?
There is no adverse effect on most common plants, and the impact on special rare plants can be consulted by relevant flower experts.
27 Do sunshades, trees and awnings affect the performance of Low-E glass?
These objects can restrict the heat and light entering the room through the glass window, that is, block part of the solar energy from passing through, but it does not affect the performance of Low-E glass.
28 Which direction of Low-E glass is best installed?
In winter, no matter which direction Low-E glass faces, it will not affect its function, because it mainly reflects indoor heat. But it works best when installed towards the north, after all
While Low-E glass prevents indoor heat loss, it also somewhat restricts solar radiation. l In summer, Low-E mainly reflects outdoor heat, so which way it faces
The installation direction is suitable, but the effect of installation in the east, west and south direction is the best, because it can also reduce the penetration of solar energy.
29 How long does the Low-E film last?
The duration of the coating layer is the same as the duration of the sealing of the hollow glass space layer.
30 What is the effect of combining Low-E glass and tinted glass?
There are three ways of combining: plating Low-E film on colored glass, synthesizing hollow glass with colored glass, and synthesizing laminated glass with colored glass. Colored glass can further reduce combined glass.
The shading coefficient of the product restricts more direct solar radiation from entering the room. Therefore, the combined use of these three methods has a good effect, and is more suitable for use in southern temperate and tropical regions.use. Combining with colored glass can also greatly increase its decorative effect.
Good glass can work better with good profiles.
If you are interested in getting more details ,quotation or have any other requirement, please feel free to contact with us.
Pavida Windows &Doors co.Ltd Email: lorraine@pavida.cn Tel/wechat/whatsapp:+86 13751591113
