Application of green energy-saving technology in glass curtain wall design of large public buildings

Problems such as poor thermal insulation performance, large energy consumption, poor ventilation and light pollution of ordinary glass curtain wall in large public buildings are increasingly prominent, so it is necessary to design energy-saving glass curtain wall. This paper focuses on the application of green energy-saving technology in glass curtain wall design, hoping to provide reference for energy-saving design of glass curtain wall in the future. Large public buildings; Green energy-saving technology; The design of glass curtain wall breaks the traditional boundary between window and wall, not only updates the concept and technique of modern architectural design, but also shows the new progress of modern architectural technology. However, the problem of high energy consumption caused by poor air tightness and thermal insulation performance of glass curtain wall has also attracted great attention. China's building curtain wall industry started late. At present, the main measures to improve the energy-saving and thermal insulation performance of glass curtain wall in China are still in the passive fortification design stage. Coated glass, LOW-E glass, heat reflective glass, insulating glass and aluminum profile with thermal insulation broken bridge are mainly used to reduce the structural heat transfer coefficient K, eliminate the thermal bridge of the structural system, reduce the air infiltration heat loss, reduce the area of opening window sash and improve its sealing performance. In most areas, single-layer coated glass, LOW-E glass and heat reflective glass are used for heat preservation and energy saving (compared with single-layer ordinary white glass, energy consumption can be reduced more). In buildings with high thermal insulation requirements in cold regions, insulating glass and insulating broken bridge aluminum profiles are used for thermal insulation and energy saving. In China, the application of high-tech curtain walls such as double glass curtain wall and smart glass curtain wall is still relatively backward. How to make the glass curtain wall more energy-saving has become a hot research topic. Application and key design of 1 double glass curtain wall system. The double-layer glass curtain wall consists of inner and outer glass curtain walls. The external curtain wall generally adopts hidden frame, open frame or point glass curtain wall, and the internal curtain wall generally adopts open frame curtain wall or aluminum alloy doors and windows. A relatively closed space ventilation compartment is formed between the inner and outer curtain walls. Air enters from the air inlet at the lower part of the external curtain wall and is discharged from the air outlet at the upper part to form a heat buffer layer, thus adjusting the indoor temperature. In the cold regions of our country, as long as the design is reasonable, both internal and external circulating glass curtain walls can be used in public buildings with similar cooling and heating loads. When the double-layer glass curtain wall is reasonably applied, compared with the standard energy consumption of similar buildings, the energy saving rate is about 50%. 1. 1 application of double-layer glass curtain wall system 1. 1 closed internal circulation double-layer glass curtain wall. This kind of curtain wall is generally used in cold areas in winter. In principle, the outer glass curtain wall is fully enclosed, generally composed of heat insulation profiles and hollow tempered glass, while the inner layer is generally a glass curtain wall composed of single-layer tempered glass or an openable window. The thickness of ventilation interlayer between two curtain walls is generally 120 ~ 200mm. The ventilation interlayer is connected with the exhaust pipe of the HVAC system at the ceiling to form a forced air circulation from bottom to top. 1. 1.2 open external circulation double glass curtain wall. This kind of curtain wall is what we often call a breathing double-layer glass curtain wall. The outer layer is a glass curtain wall composed of single-layer glass and non-insulated profiles, and the inner layer is an open-frame curtain wall or a unit curtain wall with heat insulation or heat preservation. In winter, when the air inlet and outlet of the ventilation layer are closed, the temperature of the air in the ventilation layer rises under the irradiation of sunlight, forming a greenhouse effect, effectively raising the temperature of the inner glass and reducing the heating energy consumption of the building. In summer, the air outlet of the ventilation layer is opened, and the heat in the ventilation room is taken away through the stack effect, so that the surface temperature of the inner glass is reduced and the energy consumption of air conditioning is saved. In addition, through the control of air inlet and air outlet and the design of interior curtain wall structure, the purpose of conveying fresh air from the ventilation floor to the room is achieved, thus optimizing the ventilation quality of the building. It can be seen that "open external circulation system" not only has the advantages of "closed internal circulation system" in sunshade and sound insulation, but also is more prominent in comfort and energy saving, which provides the possibility of natural ventilation and meets the physiological and psychological requirements of users to the greatest extent. Figure 1 Schematic Diagram of Ventilation Curtain Wall of Two Systems 1. 1.3 Application of Breathable Double Glass Curtain Wall System. Multi-layer double-layer glass curtain wall. The ventilation compartment of multi-layer and double-layer glass curtain wall is connected with several rooms in the horizontal direction and covers several floors in the vertical direction. Sometimes the ventilation compartment between curtain walls is neither horizontal nor vertical, and ventilation is only formed through the vents on the bottom of the outer curtain wall and the roof. In winter, the vent of the external curtain wall is closed, and the greenhouse effect formed by the ventilation interlayer is used to ensure the indoor temperature and reduce the building energy consumption; Open the vent in summer, and use the smoke window effect to form natural ventilation. Because there are few openings in the outer glass curtain wall, the system is very suitable for the environment with large external noise. However, the sound of each room in the building is easy to spread through the ventilation interlayer, causing internal sound interference. The openable double-layer glass curtain wall can be completely opened, and there is no clear air inlet and outlet, so it is difficult to form natural ventilation by using the smoke window effect. In summer, the outer curtain wall is completely opened, which can be used as a sunshade device to reduce the solar radiation received by the inner curtain wall; In winter, the external curtain wall is closed to form an air buffer layer to enhance the thermal insulation performance of the building. The openable outer glass curtain wall reduces the wind pressure of the inner glass curtain wall, which helps to prevent rainwater from entering the inner glass curtain wall, so the windows of the inner glass curtain wall can be opened all the time, which is beneficial to natural ventilation. 1.2 rational design of double-layer glass curtain wall system Under the conditions of climate and building type suitable for double-layer glass curtain wall, we must first distinguish the different performance requirements of inner and outer glass in internal circulation system and external circulation system. The inner curtain wall of external circulating glass curtain wall is generally composed of glass curtain wall with good thermal insulation performance, which mainly plays the role of thermal insulation in winter and summer. The external curtain wall is usually a single-layer glass curtain wall, which mainly plays a protective role, protecting the sunshade device in the interlayer from the bad outdoor weather, and at the same time, the opening set in the facade can adjust the ventilation of the interlayer; The internal circulation system is an internal curtain wall, which is generally an ordinary single-layer glass curtain wall, and the external curtain wall has good performance. Secondly, design the width of air interlayer reasonably. If the width of the interlayer is not enough, or there are too many floors ventilated in series, the chimney will have obvious benefits, resulting in no ventilation or effective ventilation. For public buildings with high indoor heat, in the transitional season or summer, poor ventilation is not conducive to heat dissipation at night, which will prolong the air conditioning time. Furthermore, it is also necessary to design sunshade blinds reasonably. If the air interlayer is not designed with sunshade blinds, the overall sunshade coefficient will not be increased by 10%, but it will waste and occupy more space. For the external circulation system, in order to obtain better natural ventilation effect, its interlayer width is generally not less than 400 mm Sometimes, in order to reduce the occupation of building area by curtain wall structure and reduce the distance between two curtain walls, it is necessary to use mechanical auxiliary interlayer ventilation, and the interlayer distance is generally not less than100 mm. For the internal circulation system, it is very important to reasonably design the mechanical ventilation volume of the cavity under different working conditions, improve the ventilation start-up temperature, and rationally design control strategies to save energy consumption. The experiment and theoretical calculation show that the heat insulation and ventilation effect is the best when the louver is located outside the middle of the interlayer 10% ~ 20%. 2 Application of new materials in the design of glass curtain wall of large public buildings 2. 1 Thermal reflective coated glass, also known as solar control coated glass, refers to the coated glass with the function of reflecting solar energy. Its biggest feature is that the coating can transmit visible light, and can reflect the far infrared ray which plays a heating role to the outside. At the same time, the solar heat energy absorbed by the glass material is isolated by the coating, so that the heat is mainly distributed to the outdoor side, and the thermal effect of the sun is reduced as much as possible. Its reflectivity to solar light can reach 20%-40%, and it has good shading performance. This kind of glass can control the indoor thermal environment, reduce glare and dispersion, make indoor light soft and comfortable, thus reducing the indoor air conditioning load and equipment investment, and achieving the purpose of saving air conditioning energy consumption. 2.2 Low-emissivity glass and multifunctional coated glass Low-emissivity glass and multifunctional coated glass are also called heat-insulating coated glass. These materials are characterized by high transmittance for visible light and high reflectivity for infrared radiation, especially far infrared radiation. They can let 80% of visible light enter the room, and at the same time keep more than 90% of the long wave radiated by indoor objects indoors, which has good transparency. Low-emissivity glass and multifunctional coated glass greatly improve the utilization rate of energy, can selectively transmit solar energy in cold areas and reflect most of the thermal radiation indoors, which plays a very good role in heat preservation and energy saving in heating buildings. Low-emissivity glass and multifunctional coated glass are generally used to make insulating glass, but they are not used alone. Compared with other glasses, the heat transfer coefficient of insulating glass will be very low. Compared with multifunctional coated glass, low emissivity glass has the same heat transfer control function, but multifunctional coated glass is superior in reducing heat entry. Conclusion In a word, the use of glass curtain wall is a trend of modern architecture, and the energy consumption of glass curtain wall and glass window accounts for about 50% of the total energy consumption of the building. To achieve the goal of ultra-low energy consumption, it is an important aspect to use high-performance energy-saving glass for glass curtain walls and windows. As long as the design of glass curtain wall is reasonable, suitable glass is selected and reasonable structure is adopted, the requirements of energy-saving standards can also be met. Double glass curtain wall is energy-saving, environmentally friendly and comfortable, and is suitable for public buildings with similar cold and heat loads. Compared with the standard energy consumption of similar buildings, double-layer glass curtain wall has obvious energy-saving effect. References: [1] Jingying. Study on the external sunshade design of glass curtain wall [J]. Shanxi Architecture, 2009, (04):53-54 [2] Liu Weijie, Ji Ye. Energy-saving design of glass curtain wall [J]. Doors and Windows, 2009, (02): 10.