To protect the original ecological environment, passive low-energy buildings are especially worth promoting in plateau areas, and the climate characteristics of plateau areas determine that there are certain particularities in the selection of door and window materials for passive houses. Due to the low air pressure in the plateau area, the insulating glass produced in the plain area cannot be directly applied to this area. Even if it is produced locally, the internal air pressure of the insulating glass must be consistent with the local air pressure. In addition, since the U value will increase significantly when the insulating glass is placed horizontally, it is not suitable for lighting roofs. Vacuum glass does not have the above problems, and it can be said to be the best choice for doors and windows of passive low-energy buildings in plateau areas.
Figure 1 How to choice the doors and windows of passive low-energy buildings in plateau areas.
Application of vacuum glass in passive low-energy buildings
At present, some international designers have designed vacuum glass in various energy-saving buildings. For example, Dr. Werner Sobek, a professor at the University of Stuttgart in Germany, the dean of the Institute of Architectural Structure Design, and a world-renowned architect used the vacuum glass provided by Xinliji in the active house project. The construction site of the project is located in the center of the Weissenhof Siedlung complex completed in the 1920s in Stuttgart, which is the very commemorative "White Court Settlement" architectural exposition in the history of modern European architecture. Many famous designers in Europe are involved in the architectural design of real estate in this area. They use new building materials and new building methods to design living facilities for modern urban residents.
The insulating glass was invented by Americans in 1865. It is a new type of building material with good heat insulation, sound insulation, aesthetics, and applicability, and can reduce the self-weight of buildings. It uses two (or three) pieces of glass and uses high strength and high strength. The airtight composite adhesive is used to bond the glass sheet to the aluminum alloy frame containing the desiccant to form a high-performance sound-insulating and heat-insulating glass. Insulating glass has many properties superior to ordinary double-layer glass, so it has been recognized by countries all over the world. Insulating glass is to separate two or more pieces of glass evenly with effective support and bond and seal the periphery so that a dry gas is formed between the glass layers. Space glassware.
Figure 2 The main constituent materials of insulating glass
The main constituent materials of insulating glass include glass, aluminum spacer, angle plug, butyl rubber, polysulfide glue, desiccant, argon gas for filling insulating glass, etc.
The main equipment for insulating glass production and processing includes the insulating glass production line, insulating glass sealing robot, insulating glass butyl coating machine, molecular sieve filling machine, aluminum strip transmission frame, etc.
The high-end glass products used in high-end energy-saving buildings mainly include vacuum glass and three-glass two-cavity insulating glass. Insulating glass products have been applied earlier, and the technology is relatively mature. High-end products reduce the U value by selecting high-quality Low-E and increasing the number of Low-E layers, thickening the thickness of the hollow layer, and filling argon. Vacuum glass uses a basic configuration that can achieve a lower U value.
Figure 3 The three-glass two-cavity insulating glass
The advantages of vacuum glass in the application of passive low-energy buildings in plateau areas
Vacuum glass has already shown obvious comprehensive performance advantages, so what are the unique advantages of vacuum glass applied in plateau areas? The following is an overview.
1. Wide application area, especially suitable for plateau areas.
High altitude and low air pressure are the characteristics of plateau areas. Taking the United States as an example, the altitude of the New York area is about 50m, while the altitude of the Salt Lake City area is 2300m, and the altitude of the Denver area is 3600m. Taking Colorado's average altitude of 4000m as an example, it is roughly estimated that the air pressure in Colorado is 25kPa lower than that in New York. If the insulating glass is made in New York, its internal pressure is 1 standard atmosphere. A pressure difference of 2,500 kg can easily cause the insulating glass to burst, and there are actual engineering cases to prove this point.
In addition, tourism data shows that altitude sickness of tourists often occurs on the way, which is mainly caused by the constant change of pressure difference on the way, and the pressure difference will be even greater if the altitude of some routes exceeds 5000m. For the same reason, insulating glass produced in plain areas also has this problem when it is transported to plateau areas. During the transportation process at high altitudes, the pressure difference withstood by the insulating glass will continue to change, which is more likely to cause glass swells and cracks. If it is produced locally, technical attention should also be paid to these issues.
Since the vacuum glass is in a vacuum state, there is no problem of expansion and cracking when the insulating glass is transported to plateau low-pressure areas, so it can be applied to plains and high-altitude areas. Theoretically speaking, the more in the plateau area, the smaller the pressure difference on the vacuum glass, the smaller the stress on the glass, and the higher the safety.
Figure 4 The three-glass two-cavity insulating glass 2
2. The U value does not change when placed horizontally, which is suitable for lighting roofs and sunrooms
The plateau area is full of sunshine, which is very suitable for the use of daylighting roofs and sunrooms. When the vacuum glass is applied to the slope of the building, the plane daylighting roof, and the sunroom, there is no problem that the gas convection and conduction will increase greatly when the insulating glass is placed flat... Taking the products in a glass curtain wall construction project as an example, the change of U value when the glass is placed vertically, at a 45° angle, and horizontally is calculated respectively. It can be seen that the U value of the three-glass two-cavity insulating glass has changed from 0.67 W/(㎡*K) to 0.97 W/(㎡*K), which is significantly larger, while the U value of the vacuum glass has remained unchanged.
3. The U value is low, and it can be even lower in the future
Among the glass used in a glass curtain wall construction project, the composite vacuum glass of Glass Manufacturering Company has the lowest U value. The U value of vacuum glass can be even lower, such as using Low-E glass with lower emissivity, increasing the number of Low-E glass layers, etc.
Taking the insulated + semi-tempered vacuum glass in a glass curtain wall construction project as an example, if single Low-E glass with emissivity of 0.06 and 0.03 is used, the U value can reach 0.50 and 0.41 W/(㎡*K); The U value of double Low-E glass with emissivity of 0.06 and 0.03 is lower, which can reach 0.41 and 0.35 W/(㎡*K). Low U value can not only reduce building energy consumption but also effectively prevent indoor condensation, which has obvious advantages in passive low-energy building applications. At the same time, choosing vacuum glass with a low U value can reduce the frame-to-window ratio of the entire window, increase the light transmittance of the entire building, and make the living environment more transparent while keeping the U value of the entire window unchanged.
The total solar energy transmittance and light-to-heat ratio of glass can be adjusted by choosing different Low-E glasses, especially in my country's vast territory and diverse climatic conditions. The optical and thermal properties of vacuum glass, such as visible light transmittance, light-to-heat ratio, and solar energy The total transmittance can be adjusted according to the needs of the region and orientation.
4. The thickness is thin, and it can be thinner in the future.
It can be seen from the product parameter table of a glass curtain wall construction project that when the U value is close, the thickness of the vacuum glass is much smaller than that of the three-glass two-cavity insulating glass, which can reduce the thickness of the entire window and reduce the building load.
On the other hand, it can increase the usable space of the building. If floor-to-ceiling windows are used in the building, the usable area of the building can be increased.
In the previous applications of vacuum glass, the structure of composite vacuum + insulating glass was generally used, mainly from the perspective of mechanical safety. If the safety requirements are relatively high, the use of vacuum + lamination can reduce the thickness of the composite vacuum glass.
Vicat 82 profiles are used in a glass curtain wall construction project, and the thickness of the entire window is 82mm, which is relatively thick. If low U-value vacuum glass is used and high-performance profiles matching vacuum glass are developed, the thickness and weight of the entire window can be reduced, which not only reduces the burden on the hinges in the window frame, reduces costs, but is also convenient for users to use.
5. Long life, even if the hollow fails, the U value does not change much.
The strong ultraviolet radiation in the plateau area makes the edge sealant of the insulating glass very easy to fail, while the vacuum glass is sealed with inorganic materials, does not contain organic glue materials, and undergoes strict high-temperature vacuum exhaust during processing under qualified process conditions. In harsh environments such as high temperature, low temperature, high humidity, and ultraviolet radiation, there will be no problems such as performance attenuation, aging failure, etc. In addition, there is a getter material placed inside the vacuum layer. After rigorous climate simulation tests and theoretical calculations, the vacuum life is more than 50 years. In fact, after nearly 3,000 days of follow-up testing of LIJIANG Glass under outdoor natural conditions in low-altitude areas, the thermal conductivity of vacuum glass samples has little change, fluctuating within 5%. In the vacuum + hollow composite structure, even if the insulating glass fails, it will not have a large impact on the U value.
On the other hand, the Low-E layer in the vacuum glass is located inside the vacuum layer. Because of the high vacuum inside the vacuum glass, it can protect the Low-E film and ensure the low U value of the vacuum glass for a longer period, improve product life.
6. Good sound insulation effect.
The sound insulation of composite vacuum glass can reach 41dB, which is better than that of three-glass two-cavity insulating glass. Vacuum glass can effectively block traffic noise in the middle and low-frequency bands, enhancing its practicability in blocking life noise.
A few questions about vacuum glass
Vacuum glass is still a new thing in the industry. While it has received widespread attention, everyone can't help but have some doubts. The following will introduce several issues of general concern.
1. Lifespan issue
The life of vacuum glass includes two aspects, one is the vacuum life, and the other is the mechanical life. Vacuum life needs to be guaranteed by technology, which has been introduced in detail above. It should be pointed out that each piece of vacuum glass produced by regular manufacturers must undergo strict testing before leaving the factory, to prevent some unqualified or even counterfeit and shoddy products from entering the market. Strict supervision is required for some shoddy vacuum glass. For example, products that do not use high-temperature exhaust, no getters, or even fake getters must be eliminated to ensure the reputation of vacuum glass in the industry.
Mechanical life, on the one hand, scientific and strict product design and production processes are required to manufacture semi-tempered vacuum glass and tempered vacuum glass to improve mechanical strength; on the other hand, composite hollow or laminated methods can be used to improve safety.
2. Cost issue
The issue of price is what everyone is more concerned about. There is not much difference in price between composite vacuum glass and three-glass two-cavity insulating glass, while vacuum glass is more cost-effective. At the same time, through automation to improve the yield, increase production capacity, use new materials and new processes, etc., there is still a lot of room for price reduction of vacuum glass in the future.
3. Supply issues
With the progress of vacuum glass industrialization, the problem of product supply will be solved. Xinliji's automated production line has entered the final stage of commissioning. After the commissioning is completed and the new line is in operation, it can reach the designed production capacity of 500,000 square meters per year. On this basis, the next generation of new production lines with higher cost performance and more suitable for promotion has been designed and tested.
4. Engineering application
Engineering application is the best standard for testing products. The vacuum glass of a glass manufacturing company has been applied to many buildings and has created many international and domestic firsts, such as the world's first full vacuum glass building and large-area vacuum glass curtain wall project— Glass Manufacturer has the largest vacuum glass application area and the most application cases in the world. Table 6 shows the vacuum glass application engineering projects of glass manufacturing companies, and the figure shows several latest engineering application examples.
Compared with insulating glass, vacuum glass has comprehensive performance advantages, and is suitable for popularization and application in high-end doors and windows of low-energy buildings, especially in plateau areas. The vacuum glass industry in some developing countries (such as China and India) ranks among the top in the world in terms of patented technology, industrialization level, and promotion and application. It should receive sufficient attention.
On the one hand, it is necessary to continuously improve building energy-saving standards so that energy-saving products can truly Application, on the one hand, it is necessary to increase support for the industrialization of vacuum glass, so that the leading technology that is rare in China's building materials industry can be developed faster. As the new darling of glass deep processing, vacuum glass will be better applied in passive low-energy buildings in plateau areas.