Abstract: China is in a critical period to promote the construction of small and medium-sized cities. Green building can solve the resource consumption and environmental problems caused by high-speed urbanization. Based on the evaluation system of green buildings in China, this paper tries to discuss the problems and solutions in the implementation of green buildings in small and medium-sized cities.
introduce
With the growth of national economy, the construction of small and medium-sized cities has become an important basis for conforming to the trend of economic and social development, implementing industry to feed agriculture and narrowing the gap between urban and rural areas. With the promotion of economy, people's living standards have improved, and the demand for housing has also increased. From the material concept of "living in peace" in the past, we gradually began to pursue the spiritual concept of "green", prompting the construction industry to move towards "green development, circular development and low-carbon development" [1].
1 Development Status of Buildings in Small and Medium-sized Cities
1. 1 extensive development model
1978-20 12 The buildings in small and medium-sized cities in China increased from 17.9% to 52.6%, with an average annual growth rate of 1.02 percentage points [2]. Behind this rapid development is unsustainable extensive development at the expense of resources and environment. It took us decades to complete the industrialization road of western countries for one or two hundred years. While promoting the rapid development of industrialization, urban construction is also facing severe challenges. The extensive development of architecture not only devours a lot of agricultural and ecological land, but also causes many problems such as lax supervision, too much construction waste can not be effectively treated, and real estate planning simply pursues economic benefits.
1.2 Energy consumption of existing buildings
The dependence of building operation on energy and resources such as water, electricity and gas is very obvious. Before 2000, most of the urban construction and development were non-green energy-saving buildings, accounting for 80% of the urban construction area. A large number of non-green and energy-saving existing buildings not only aggravate the consumption of resources and energy, but also cause irreversible environmental pollution. According to statistics, 60% of carbon emissions come from the reconstruction and expansion of buildings and the normal operation of their functions, and only 30% comes from automobile exhaust. China's building energy consumption accounts for more than 40% of the national total energy consumption, far exceeding the energy demand of other industries.
1.3 environmental resources of small and medium-sized cities
Green building itself solves the problem of environmental pollution caused by architecture from the source of construction and development. Get rid of the previous "build first and then green" secondary investment. Relying on the environmental foundation of small and medium-sized cities, the hydrology, geology and geomorphology after regional development are consistent with those before development through decentralized and small-scale measures. Take Hulunbeier as an example. Woodland accounts for 50% of the city's total land area, and the total water resources are 28.66 billion cubic meters. The per capita water resource is 1. 1.00 million cubic meters, which is 4.66 times of the national average. Compared with the big cities that have been affected by smog and water pollution, it is obvious that the construction of small and medium-sized cities must choose the concept of green building development, which urges us to protect the few natural heritages from the source.
2 the necessity of applying green buildings in small and medium-sized cities
2. 1 people's own needs
Due to the continuous migration of population, the urbanization scope of small and medium-sized cities has been expanding, and the subsequent architectural development has mushroomed. Dense population, rising construction land prices and increasing public demand for materials have forced cities to expand outward. Just like the principle of self-organization in synergetic theory, urban expansion is not guided by the government, but the inevitable result of public choice, which is also the inevitable process of the construction of developing countries.
2.2 ecological environment demand
Prospective Industry Research Institute's "20 16-202 1 China Intelligent Building Industry Analysis Report" shows that the total energy consumption of buildings in China is increasing year by year, accounting for 27.45% of the total energy consumption. Due to the acceleration of urbanization, this proportion will rise to about 35%. At this rate, by 2020, the building energy consumption may reach 10.89 million tons of standard coal, and the air conditioning load in summer is equivalent to10 Three Gorges power stations working at full capacity [4]. With the development of small and medium-sized cities, it has become a common practice to demolish old buildings and build new ones, and demolition has brought a lot of immovable construction waste. The environmental and ecological problems interwoven between new buildings and existing buildings are expanding, and we must face up to these developing problems.
3 problems in the application of green buildings in small and medium-sized cities
3. 1 cognitive problems
Low energy consumption brings low use cost and long-term environmental benefits of green buildings. These advantages cannot be directly transformed into market forces and consumer demand, nor can builders and consumers actively participate in the process of promoting the development of green buildings. The uncertainty of environmental benefits of green building technology, the long-term appearance of benefits, the efforts of the government and the short-term pursuit of benefits by builders all affect the promotion of green building technology.
3.2 Technical problems
At present, the biggest obstacle to the development of green buildings in small and medium-sized cities is not the backwardness of green building technology, but the lack of technical training for related enterprises, which can not keep pace with the times and understand advanced green technologies. This will affect the enthusiasm of enterprises for green building and slow down the promotion of green building. The university construction in small and medium-sized cities is not perfect, and the integration of university scientific research and enterprise technology application has not been formed. The architectural development of small and medium-sized cities can only passively accept the "emerging technology" of "green building", and it is impossible to develop and study the green building system that integrates with the local environment, economy and culture, which seriously restricts the application and promotion of green building technology.
3.3 Cost issues
The cost problem has always been the main reason that hinders developers from promoting green buildings. Green buildings not only have a slightly higher cost of material selection than ordinary buildings, but also need to spend a lot of money on ancillary facilities around buildings in order to save water, land and energy. In recent years, the government has continuously introduced preferential policies for green buildings, but it is a drop in the bucket for the economic interests of developers. According to the incremental cost statistics of green buildings in China City Science Research Institute in 20 14 148 [2], the incremental costs of one-star, two-star and three-star green buildings for residential buildings are 23.9 yuan /m2, 70.9 yuan /m2, 13 1.8 yuan /m2, respectively.
4 implementation strategies of green buildings in small and medium-sized cities
4. 1 Green transformation of existing buildings
The green transformation of existing buildings mainly focuses on the heating and living energy consumption of buildings, which is also 70% of the building energy consumption. The climatic conditions, architectural forms and economic development in China are very different, so the existing energy-saving renovation measures for buildings should be adapted to local conditions. The reconstruction of existing buildings in cold areas mainly depends on the thermal insulation of building external walls. Improving the thermal performance of envelope, improving the heat transfer coefficient of doors, windows, roofs and floors, strictly implementing the ratio of windows to walls and improving the air tightness of doors and windows can reduce building energy consumption. Application of renewable energy. Small and medium-sized cities are generally small in population and rich in resources. The auxiliary facilities of public buildings and houses can realize simple self-sufficiency by using technologies such as wind energy and solar energy. For example, solar lighting, rainwater reuse, small-scale wind power generation in the square, hydropower landscape and so on. The water cycle in China not only reduces energy consumption, but also contributes to reducing urban waterlogging disasters and building a sponge eco-city.
4.2 Passive Architectural Design
Passive design refers to the building system that maximizes the thermal insulation and air tightness of the building envelope, makes full use of passive technical means such as natural ventilation, natural lighting and solar radiation, minimizes the demand for heating and air conditioning, and realizes harmony with nature on the basis of comfortable indoor environment.
① Replacing central air conditioning refrigeration system with efficient natural ventilation. The principle of wind pressure and hot pressing is applied to the development or reconstruction of original buildings. Because of the pressure difference when the wind passes through the building, air flows into the room from the windward hole, and indoor air is discharged from the leeward hole, forming effective natural ventilation with wind pressure. If the indoor temperature is higher than the outdoor temperature, the upper pressure of the building space is higher and the lower pressure is lower. When there are air holes in these positions, air will enter the upper air holes through the lower openings and flow out.
② Use natural lighting instead of lighting and heating. Large public buildings adopt passive design concept, considering the angle between the building orientation and the sun, and natural light enters the room through the glass roof to achieve the effect of natural lighting and improving indoor temperature. The roof is equipped with automatic shutters to avoid too much direct sunlight in summer and reduce the indoor temperature.
4.3 Reasonable positioning of planning cost
The application cost of green building is mainly the technical research in the early stage. As shown in figure 1, most of the expenses are in the process of R&D and material production. Design and construction can be used for reference in many projects, and later operation is the key to project profitability. For builders and consumers, they are not directly responsible for the production of expensive R&D and green building materials, but participate in the stages of material selection, design, construction and post-maintenance. As far as the whole value chain is concerned, both builders and consumers participate in the value-added and profitable part of the whole life cycle cost.
In the cost of green building, we mainly analyze not the single cost of the building itself, but whether its incremental cost can bring later benefits. See Figure 2 and Figure 3 for the survey statistics of 2 1 green building projects cited by Sun Daming and others. The higher the positioning of general projects or the higher the stars selected, the greater the corresponding incremental cost. The reasonable positioning of green buildings and the choice of energy-saving grades by builders and consumers are the key to affect the incremental cost.
5 concluding remarks
The application of green building in small and medium-sized cities should first realize the connection between green building technology, urban planning, landscape planning and municipal facilities; Secondly, the government should use rewards and punishments in the implementation of green buildings to realize the development from a single green building to a green city; Finally, promote consumers and builders to guide the development of green buildings in small and medium-sized cities, and implement the technical concept of green building development before the development and construction of small and medium-sized cities with feasible schemes. To truly realize the implementation of environmental protection before urban development and utilization will be the direction of our continuous efforts.
The above urban green building application analysis was collected by Zhong Da Consulting Company.
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