1. 1 Analysis of environmental benefits of green buildings
At present, there is not much research on the environmental benefits of green buildings, and it has only begun to develop in recent years. Li Jing and Tian Zhe [6] studied the incremental cost-benefit of green buildings from six aspects: land saving, energy saving, water saving, material saving, indoor and operation. Wu Junjie, Ma Xiuqin and others [7] calculated the economic benefits of Tianjin Sino-Singapore Eco-city by calculating the annual load of residential buildings, CO2 emission reduction and synergistic effect. Liu Xiujie [3] conducted a comprehensive environmental impact assessment of green buildings based on life cycle theory and externality theory; Yang Wan and others [8] analyzed the economic and environmental benefits of energy-saving transformation technology with engineering examples; Cao Shen and Dong Cong [9] analyzed the contents and characteristics of various costs and benefits in the whole life cycle of green buildings, and quantitatively calculated the environmental benefits and social benefits.
The evaluation standard of green building (GB50378-2006[ 10]) is a building that can save resources (energy, land, water and materials) to the maximum extent, protect the environment and reduce pollution, provide people with healthy, applicable and efficient use space and live in harmony with nature. According to the definition, the environmental benefits of green buildings can be divided into energy-saving environmental benefits, water-saving environmental benefits, land-saving environmental benefits, material-saving environmental benefits and environmental quality improvement benefits. According to different forms of green building benefits, environmental benefits can be divided into CO2 emission reduction benefits, health benefits and building materials life extension benefits. With the rapid economic development in China, CO2 emissions will inevitably increase [1 1]. According to the investigation report of the United Nations Environment Programme, if CO2 emission reduction is not realized, the global temperature will increase by 0.3℃ on average every ten years, and the survival and development of human beings will be seriously threatened. Green building takes "four festivals and one environmental protection" as the goal, and combining with the main environmental problems in the world today, energy saving is the most important, so this paper mainly studies the energy-saving environmental benefits of green building.
1.2 analysis of energy saving and environmental benefits of green buildings
In order to meet the challenges of global climate change, shortage of resources and energy, and deterioration of ecological environment, human beings are following the concept of carbon cycle, developing circular economy, building low-carbon ecological cities and popularizing low-carbon living buildings. Green buildings can save energy by making full use of solar energy, adopting energy-saving building envelope and heating and air conditioning, and reducing the use of heating and air conditioning. The main energy-saving measures for green buildings [12] are as follows: (1) Energy-saving exterior envelope is the most important content in building energy-saving design, and energy-saving measures for exterior envelope refer to effective measures for thermal insulation from roof, exterior wall, doors and windows. For example, by increasing the area of doors and windows to increase the lighting and ventilation area, improve the thermal insulation of materials and improve the sealing of doors and windows, and finally achieve the effect of energy saving.
(2) Intelligent Technology Energy Saving Intelligent technology energy saving is to optimize the control of air conditioning units, fresh air units, refrigeration units and lighting facilities to minimize the power consumption of buildings. In building energy consumption, lighting energy consumption accounts for a large proportion. Indoor and outdoor lighting systems should comprehensively consider energy-saving light sources, lamps and accessories. In order to save electricity, green buildings usually use high-efficiency new energy-saving lamps, and public areas use high-efficiency light sources, high-efficiency lamps and delay or voice-activated switches, while paying attention to energy-saving measures in natural lighting areas. In addition to energy-saving lamps, energy-saving measures also include the installation of energy-saving elevators, HVAC, room temperature regulators, energy recovery systems and other high-efficiency energy-saving equipment and systems, which also require incremental cost investment. HVAC system should control the energy efficiency ratio of equipment and the transportation efficiency of pipe network system. In buildings with central heating or air conditioning systems, fresh air systems can be installed to recover energy, which can achieve relatively objective economic and environmental benefits.
(3) Renewable energy conservation Renewable energy refers to natural energy that can be generated repeatedly, including solar energy, wind energy, hydropower, geothermal energy, ocean energy, tidal energy and biomass energy. It is a new non-fuel energy system in line with the sustainable development strategy. The renewable energy sources used in green buildings are usually solar energy and geothermal energy, which are the most easily available renewable energy sources.
2 Suzhou energy-saving environmental benefits analysis
2. 1 main research method: market value method.
The market value method is a resource evaluation method to determine the price of natural resources with the current market price as the price standard. It is a method to determine the value of the evaluated resources by comparing the market prices of the same or similar resources with the evaluated objects. By comparing the energy consumption of green buildings with that of benchmark buildings, the energy saving of green buildings in Suzhou by the end of 20 12 is calculated. Then the energy consumption is converted into standard coal and carbon dioxide emission equivalent; According to the market price of CO2, the benefit is calculated. In this way, we can directly see the reduction of CO2 brought by green building energy saving, which will reduce the degree of greenhouse effect. At the same time, it can also obtain the economic benefits brought by green building energy saving.
2.2 Carbon dioxide transaction price
Clean Development Mechanism (CDM) is one of the three flexible compliance mechanisms stipulated in the JD.COM Protocol, a carbon trading mechanism jointly implemented by developed and developing countries, and the only carbon trading mechanism in China at present. Therefore, refer to the "cer" of CDM projects that can be traded at the current contract price [13- 14]. Because this paper studies the environmental benefits before 20 12 years, referring to the paper of Liu Xiujie [5] in 2012 years, the emission reduction value of CO2 in that year was about 160 yuan/t.
2.3 benchmark building
The Design Standard for Energy Efficiency of Public Buildings (GB50 189-2005[ 1]) takes the public buildings built in the early 1980s as the basis for comparative energy consumption, and is called "benchmark building".
2.4 data processing
The useful data obtained directly in this paper include the declared building area, total energy consumption and energy saving rate of green buildings. There are 85 useful data of declared building area, 50 data of total building energy consumption and 56 data of energy saving rate (limited to the length of the article, I won't list them here). By the end of 20 12, the total area of 85 green buildings in Suzhou was 2,850,750 m2, as shown in Table 2. After data sorting, there are 36 groups of useful data. After calculation, the energy consumption per unit area of green building is13.14kwh/m2a ~154kwh/m2a, and the corresponding energy consumption per unit area of benchmark building is 37.38kwh/m2a ~ 346.03kwh/m2a. Their distribution in each range is shown in Figure 5 and Figure 6.
Data of energy consumption per unit area and total energy consumption of benchmark buildings can be calculated by formulas (1) and (2): energy consumption per unit area = total energy consumption of buildings/declared building area. As can be seen from the figure, the distribution of energy consumption per unit area is uneven in both green buildings and benchmark buildings, so this paper uses the weighted average method to get the average energy consumption per unit area of green buildings and benchmark buildings. See Table 3 for the specific proportion and energy consumption. According to Table 3, the average unit energy consumption of green buildings and reference buildings are: average unit energy consumption of green buildings = σ XE = 48.49 kWh/M2a = σ XE =131.78 kWh/M2a, The total energy consumption of green buildings in Suzhou before the end of 20 12 is: (131.78-48.49) × 285 According to the CO2 emission reduction value of 20 12 years, the environmental benefits of green buildings in Suzhou will be/by the end of 20 12 years.
3 Conclusion
According to the analysis and calculation of energy-saving environmental benefits, it can be seen that vigorously developing green buildings can not only effectively alleviate the greenhouse effect, but also echo the development of low-carbon economy and ecological buildings [15], which can bring huge economic benefits. At present, China has gone through a "light green" stage and is moving from a "pan-green" stage to a "dark green" stage. Therefore, China's construction field should closely focus on the objectives and requirements put forward by the Green Building Action Plan, and make persistent efforts to develop green buildings.
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