Discussion on Energy Saving of Thermal Insulation Performance of Exterior Wall of Building Envelope
If you select the "hot topic of the year", "energy saving" is undoubtedly one of the most frequently appearing topics in various media. After the reform and opening up, China's social economy has developed rapidly, and it has made rapid progress in the construction field. However, statistics show that while China's rapid economic growth, the energy consumption per 10,000 yuan of GDP is 3 to 11 times higher than that of developed countries, and the carrying capacity of resources and the environment is nearing its limit. If the current production mode and consumption mode cannot be changed, it will inevitably further increase the pressure on resource shortage. As early as the 1970s, the concept of building energy efficiency was formally proposed. The core of building energy efficiency is to reduce building energy consumption and improve energy efficiency in buildings. At the same time, building energy conservation needs to be based on the premise that it does not affect people's feeling of comfort, that is, room temperature is not lower than 18° in winter and not higher than 26°C in summer. For more than 30 years, oil and energy issues have been the focus of the world. The energy problem in China is even more revealing: building energy consumption continues to increase rapidly. China's building energy consumption accounts for 27.6% of the country's total energy consumption. More than 80% of new building construction is high-energy buildings. China's oil consumption is second only to the United States, coal-burning tension, power cuts, northern winter heating, and refined oil prices have risen. Energy consumption has become an unbearable burden. China is facing a real energy crisis. Building energy conservation is imperative and imperative. 1 China's energy consumption status China's long-established extensive production and consumption patterns have led to low energy use efficiency, which has further aggravated the contradiction of energy shortage. In 2003, China became the second largest oil consumer in the world after the United States. Since last year, China’s demand for crude oil consumption has continued to grow at a rate of more than 10% per year. It is estimated that by 2020, China's oil dependence will reach more than 55 percent. It can be seen that while China's energy consumption demand is strong, import dependence is increasing, which makes the domestic economy more constrained by the international situation. We are at another historical juncture in realizing the great rejuvenation of the Chinese nation. Faced with a series of serious problems such as resource depletion and environmental degradation, we must study the general trend of building energy conservation development and seize opportunities to promote the advancement of building technology and building energy conservation in accordance with the requirements of sustainable human development and guided by scientific ethics. Industrial development. 2 Foreign building energy-saving strategies After several energy crises, countries around the world have proposed to control the growth of fossil energy use, improve energy efficiency, develop new energy and renewable energy, and protect the environment. The energy conservation of the construction industry, which is a large energy consumer, has received great attention. In the United States, the construction industry is one of the pillars of the economy. Accordingly, building energy consumption also accounts for a significant proportion of US energy consumption. Part of the federal government's energy management plan developed by the US federal government involves building energy standards. In states with more developed economies such as California and New York, building energy efficiency standards are stricter than federal government standards. The “Building Technology Plan†proposed by the US Department of Energy considers every aspect of building construction to be relatively complete. The “Green Building Association of the United Statesâ€, which is supported by the Ministry of Energy, is also actively promoting energy conservation (the Green Building Assessment System is currently the most comprehensive and influential in building environmental assessment standards in countries around the world. In 1973, the global oil crisis broke out. Germany's energy supply relies heavily on imports, and the surge in oil prices has led to changes in German energy policy and has initiated building energy efficiency across the country. Over the years, Germany has been developing and improving building insulation technical specifications to reduce the amount of heat dissipated in the winter and to tap the potential of building energy conservation. In 1977, Germany's first building energy efficiency regulation WSVO was implemented. The requirements were put forward and standards were imposed on the heat loss of the building. In 1982, the German government put forward higher standards for building energy conservation, requiring a 25% increase on the previous basis. In 1995, Germany announced a new building energy conservation regulation WSVO'95, and the 1995 energy conservation standard was based on 1982. Increased by 30%. From February 2002, Germany implemented a new building energy efficiency specification EnEV 2002. This is the latest energy-saving specification in Germany so far. This specification embodies the research results of Germany's latest building energy-saving technology. It not only controls the energy consumption of a certain aspect of the building, but also considers the overall energy consumption of the entire building and the energy consumption in the building material production process. In the past 20 years, European countries such as Germany and Switzerland have built a large area of ​​high-comfort, low-energy housing, which has become the world's highest quality residential area with the lowest energy consumption per unit area. In terms of the envelope structure, the German wall is entirely made of external insulation technology. In the multi-layer wall, the load-bearing layer of the wall is mostly made of small concrete hollow block, clay hollow brick or aerated concrete block. The outer insulation layer selects different insulation materials according to the different decorative surfaces of the building. Single-layer walls generally use materials with low density and good thermal insulation properties. In the insulation of buildings and windows, it is recommended to use double-layer glass or even multi-layer glass instead of single-layer glass to reduce the penetration of buildings; and it is possible to fill the glass with inert gas such as argon or vacuum. Enhance the heat transfer resistance of the window. 3 China's building energy-saving requirements are very urgent. The so-called building energy-saving is to ensure the residential thermal comfort environment, through technological advancement, rational use, scientific management and rationalization of economic structure, using new insulation materials to build residential buildings in long-term use. Heating energy consumption has dropped. At present, building energy consumption has become a major energy-consuming household in China, and it is rising year by year. Statistics from the Ministry of Construction show that nearly 40 billion square meters of existing houses in the country are high-energy-consumption buildings. The annual new housing area is 162 billion square meters, of which more than 95% are high-energy buildings. According to the energy-saving design standard for civil buildings (the heating energy design goal specified in 26-95 of the Heating and Residential Design Department), the heat transfer coefficient of the external wall of China's buildings is about 26 to 3.6 times that of developed countries; the heat transfer coefficient of the roof is about 1.4 to 20 times for developed countries; in addition, the cold air penetration of doors and windows is 3 to 6 times that of developed countries. Therefore, drawing on the experience of developed countries, there is still a lot of room for improving the insulation performance of the envelope structure. Energy-saving ways to achieve building energy-saving purposes, there are various aspects of energy-saving technologies and ways, such as ventilation technology, shading technology, solar technology, water system envelope structure heat loss is large, the outer protective structure in the wall and occupied A large share. Through reasonable design, the following measures can be taken to effectively improve the thermal insulation performance of buildings and reduce energy consumption. For example, minimize the shape factor of buildings; choose the appropriate window-to-wall ratio and door and window form; Reduce the heat transfer coefficient of the roof and the external wall. At the same time, the development of building wall and the development of wall energy-saving technology is one of the most important aspects of building energy-saving technology, and the development of external wall insulation technology and 4.1 External wall insulation technology and its characteristics Xipu wall insulation is a kind of building insulation energy-saving technology that is currently being promoted. Compared with internal thermal insulation, external thermal insulation has reasonable technology and obvious superiority: external thermal insulation technology is not only suitable for new structural engineering, but also suitable for renovation of old buildings. It has wide application range and high technical content; external thermal insulation is included in the main structure. The outer side can protect the main structure and prolong the life of the building; effectively reduce the thermal bridge of the building structure and increase the effective space of the building; at the same time eliminate the condensation and improve the comfort of the living. 42 is currently more mature external wall insulation technology 4.2.1 external thermal insulation hang hang insulation materials are rock (mine) cotton, glass wool felt, polystyrene foam board (referred to as polystyrene board, EPS, XPS), pottery Granular concrete composite polyphenylene stone decorative insulation board, wire mesh frame sandwich wall board, etc. Among them, polystyrene board has been widely used in exterior wall insulation plug-in technology worldwide due to its excellent physical properties and low cost. The plug-in technology uses a bonding mortar or a special fixing member to stick and hang the heat insulating material on the outer wall, and then wipes the crack resistant mortar, presses the glass fiber mesh cloth to form a protective layer, and finally adds a decorative surface. Another method is to use a special fixing member to fix various insulation boards which are not easy to absorb water on the outer wall, and then suspend the aluminum board, natural stone, colored glass and the like on the pre-made keel to directly form the decorative surface. The external insulation of the office building of the Bank of China, designed by Mr. Pei Ming, is the design adopted. 4.2.2 Polystyrene board and wall one-time pouring forming technology" - equipment technology, new energy technology and so on. In the middle and outside of the building - gHU in the concrete and non-grid polystyrene board molding the composite wall into the bookmark3. This technology is to build the polystyrene board into the building formwork in the concrete frame-shear system, and then pour concrete, concrete and poly The benzene board is formed into a composite wall at one time. Since the main body of the outer wall and the thermal insulation layer survive once, the work efficiency is improved, the construction period is greatly shortened, and the safety of the construction personnel is ensured. This technology solves the main problems of external thermal insulation, and its advantages are obvious. The built-in polystyrene board can be a double-sided steel mesh or a single-sided steel mesh. The connection between the double-sided steel mesh polystyrene board and the concrete mainly relies on the inner steel wire mesh frame and the outer reinforcement of the wall and the adhesion of the concrete and the polystyrene board, and the bonding performance is good and the safety is high. The connection between the polystyrene board and the concrete of the single-sided steel mesh mainly depends on the adhesion of the concrete and the polystyrene board, and the anchoring force of the obliquely inserted steel bar, the L-shaped steel and the concrete wall, and the bonding performance is also good. The energy-saving discussion on the thermal insulation performance of the outer wall of the building envelope was tested. The results show that it is entirely possible to directly use concrete as a bonding agent to bond polystyrene board under the condition that the amount of cement slurry in the concrete is suitable. When the back side of the polystyrene board is treated, its adhesion to concrete is further improved. This technology eliminates the wire mesh frame, its insulation performance is improved, and the cost of the plate is again reduced. After the demonstration of its long-term durability, it can be promoted in the project. 4.2.3 Polystyrene granule insulation slurry External wall insulation The waste polystyrene plastic (abbreviated as EPS) is processed and broken into granules, and the thermal insulation mortar is prepared as a light aggregate. The technology includes an insulation layer, a crack resistant protective layer, and a barrier coating. Among them, ZL rubber powder polystyrene granule insulation materials and technology were listed as the national standard method by the Ministry of Construction in 1998. The construction method of this method is simple, can reduce labor intensity and improve work efficiency; it is not affected by structural quality differences, and the wall surface does not need to be repaired and leveled when the defective wall is constructed, and the thermal insulation slurry can be directly used for repair. At the same time, the technology solves the problem that the interface layer is easy to debond and empty, and the surface layer is easy to crack due to the poor use conditions in the external wall insulation project, thereby realizing an important breakthrough in the external wall insulation technology. Compared with other external insulation, the cost is lower when the same insulation effect is achieved, which can reduce the construction cost of the house. In addition, in the energy-saving insulation wall technology, the wall is made into a sandwich layer, and perlite, wood chips, mineral wool, glass wool, polystyrene foam, polyurethane foam, etc. are filled into the interlayer to form two layers of the insulation layer. 4.3 External wall insulation energy-saving materials Energy-saving materials are insulation materials. Insulation material refers to a material or material composite used for building envelopes or thermal equipment, impedance heat transfer, including insulation materials and cold insulation materials. The significance of thermal insulation materials is to meet the thermal environment of building space or thermal equipment, and to save energy. With the increasing intensity of energy worldwide, the significance of thermal insulation materials in energy conservation has become increasingly prominent. For the general air conditioning of residential heating, the use of insulation materials can save 50%~80% on the existing basis. Commonly used insulation materials are: polystyrene foam board, rock (mine) Cotton board, glass wool felt and ultra-light polystyrene granule insulation slurry. All of the above materials have a common feature, that is, there are a large number of closed holes inside the material, and their apparent density is small, which is also necessary as a thermal insulation material. Rock (mineral) cotton and glass wool are sometimes collectively referred to as mineral wool, and they are all inorganic materials. Rock wool does not burn, the price is lower, and it can also have a certain sound insulation effect while satisfying the thermal insulation performance. Glass wool and rock wool have many similarities in performance, but their feel is better than rock wool, which can improve workers' working conditions. Styrofoam is a material made of polystyrene resin as the main raw material, which is foamed by a foaming agent and has numerous closed micropores inside. The invention has the advantages of small apparent density, small thermal conductivity, low water absorption, good sound insulation performance, high mechanical strength, high dimensional accuracy and uniform structure. Therefore, its occupancy rate in the external wall insulation is very high. 3.5 Conclusion In summary, China's building energy conservation is imperative and has a long way to go. To develop energy-efficient buildings, it is necessary to combine the development of energy-saving materials with external wall insulation technology. While vigorously promoting the external wall insulation technology, we must also strengthen the development and utilization of new energy-saving materials, and take energy-saving technology as a breakthrough to form an industrial chain of energy-saving technology solutions, monitoring systems, enterprise supporting materials, and material utilization. Promote it to truly realize building energy efficiency. Residential buildings promote energy-saving design with the aim of improving the comfort of people's lives; and public buildings promoting energy-saving design is the key to building an intensive society. Therefore, in order to reduce building energy consumption, on July 1, 2005, China's first comprehensive national standard public building energy-saving design standard for public building energy-saving design was officially implemented. At the same time, the Ministry of Construction recently issued a notice on the strict implementation of energy-saving design standards for new residential buildings. The notice requires that the newly built buildings in the city should strictly enforce the relevant mandatory provisions of the building energy-saving design standards, and the units or individuals who violate the regulations will be severely punished. In March 2006, Shandong Province promulgated the Energy Conservation Design Standard for Residential Buildings, which is based on the calculated heating energy consumption of residential buildings in the early 1980s, requiring an overall energy saving of 65% for residential buildings. For architectural design units, buildings Energy-saving design has entered a new era. As an architect, when building an architectural design, it is necessary to take energy conservation as a responsibility, implement the national standards in a down-to-earth manner, focus on the mature intermediate technology and low-tech in-depth exploration and ingenious use, and truly find a suitable road for energy conservation in China. The concept of building energy conservation has been implemented to design. 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