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[China Aluminum Network] With the increasingly obvious impact of buildings on the environment, "passive design" as an attempt to reduce the adverse impact of construction on the environment has received more and more attention. The building is inseparable from the local climate. Traditional buildings in all parts of the country have existed for much longer than our so-called modern buildings, and they are very adaptable to the local climate.
As the impact of architecture on the environment has become increasingly apparent, "passive design" as an attempt to reduce the architectural adverse impact on the environment has received more and more attention. The building is inseparable from the local climate. Traditional buildings in all parts of the country have existed for much longer than our so-called modern buildings, and they are very adaptable to the local climate. They are not only of historical and cultural value. Most of them still have use value. It is of great significance for them to conduct research on building physics. However, we know that the traditional building figures are relatively large, generally between 0.5 and 0.7, and they have enough space to make a fuss about building physics. For our country with a large population, it is difficult to achieve a complete return to the tradition. The process of population growth and urbanization requires us to propose solutions to the existing high-volume-rate architectural forms to adapt to the urbanization. The population is concentrated while ensuring the comfort of the occupants.
1. The principle of "passive design" In the past, architects viewed facades more from a structural point of view. Building facades are often referred to as enclosures and more emphasis is placed on closures and partitions. However, for the "passive design", it is necessary to make the best use of the favorable factors in the natural environment around the building. Therefore, we regard it as a kind of semi-permeable membrane that can change with the environment, isolate the adverse environmental conditions, and introduce favorable environmental conditions into the interior. The purpose and focus of designing this kind of translucent membrane facade is to ensure the comfort of users. Without this premise, any other efforts are meaningless. Comfort can be fully quantified with specific indicators, and these indicators do not change because of the resident's skin color and ethnicity. Therefore, we say that the principle of “passive†facade design should follow: on the premise of ensuring comfort, the façade is dynamically adapted to environmental changes and the building energy consumption is reduced, which means that heating and cooling are saved as much as possible. Energy consumed by ventilation, lighting and lighting, while using the building's empty facade to generate energy.
2. Several key factors to be considered in the "passive design" a) Door and window insulation and control Improvement of insulation performance and airtight performance of doors and windows is one of the indispensable measures for building energy conservation, especially for areas with heating requirements. With the decrease of heat transfer coefficient (U value), the thermal insulation performance of doors and windows will be correspondingly increased, and the heating energy consumption will be reduced accordingly. However, when the thermal conductivity coefficient (U value) of the door and window drops below 1.5W/(m2K), heat conduction will continue to decrease. The ratio of benefit to cost (cost-benefit ratio) will be significantly reduced. The above considerations are only for heating conditions. The emphasis is still on partitions and closures. In the cooling conditions or conditions suitable for natural ventilation, the thermal insulation performance of doors and windows does not appear to be very important. In contrast, the opening methods and control methods of doors and windows will be more effective for effective energy conservation. By placing the opening and closing state of doors and windows under electric control and program control, the temperature difference between day and night and indoor air flow can be used to adjust the indoor temperature and air quality, and the energy consumed by the doors and windows is much lower than the air conditioning energy consumption.
b) External wall insulation In hot and humid areas and hot and dry areas, the annual average temperature is more than 25°C. After adding 40mm insulation layer on the wall and roof, the effect of reducing the cooling load is not obvious (both less than 5%). The contribution to the reduction of heating load in hot summer and cold winter regions is very large (up to 20%). Therefore, laying thermal insulation layers on building walls and roofs in hot summer and cold winter regions and cold regions can effectively increase the surface temperature of the outer walls, thereby saving heating energy consumption and improving indoor comfort. For the hot summer and warm winter regions, the initial investment cost of laying insulation layers and the effect of saving cooling energy consumption need to be carefully considered. In the quantitative analysis of the economic thickness of the insulation layer, we found that the economic thickness of the insulation layer for the cooling load is 40mm, more than this thickness will not significantly reduce the cooling load; for the heating load, the economic thickness of the insulation layer is 80mm.
c) The difference between the more effective shade type of sunshade (outer sunshade) and the less energy-efficient type of internal sunshade is very obvious, and it can be as much as 10°C. This result greatly changes the comfort of the interior. We know that the selection of air conditioning equipment is based on the higher temperature in the summer room. Choosing the right shade type is of great significance for reducing initial investment and operating costs.
d) Night ventilation In areas where there is a large temperature difference between day and night, the use of cooler outdoor air at night to cool the main building is a very effective means of reducing the cooling load. In two rooms with the same thermal inertness, the room temperature can be reduced by 2 to 6°C when there is ventilation at night. In addition, the temperature in a room with a large thermal inertia is about 4°C lower than that in a room with a small thermal inertia. It seems that the energy-saving effect of a room with greater thermal inertia is more pronounced, especially during daytime operation. Therefore, in the temperate and subtropical regions where the temperature difference between day and night is relatively large, the method of effectively lowering the initial investment and operating energy consumption of the ventilation and ventilation system is to design a room with high thermal inertia, and at the same time, provide the nighttime ventilation function of the outer window. However, if the outdoor humidity in the area is large or the temperature difference between day and night is not obvious, adopting a night ventilation method will not be enough to help cool the building main body, but it will destroy the comfort of the room.
e) Natural lighting Since 40% of the energy consumption in public buildings is used for artificial lighting, natural light is introduced into the room using some appropriate technology and is not affected by the angle of sunlight and clouds, and is gently distributed indoors. Energy and the creation of a healthy and comfortable indoor environment are of great significance. In a common room that does not use a daylight introduction system, the illuminance decays rapidly as the distance from the window increases, and the natural lighting conditions in the room are significantly improved after adding different types of daylight introduction systems.
The above-mentioned several factors affecting the “passive design†of door and window walls are comprehensive. The process of optimizing them is to make full use of the favorable factors in the local climate to hedge the energy consumption adjusted manually. A good application example is the double curtain wall we are currently seeing in China. This form of construction, we do not use it as a new type of product, it is better to call it a result of the combined optimization of several influencing factors. After comprehensive consideration of the wind environment, light environment, and thermal environment of the building, it optimizes the insulation, shading, ventilation, and lighting of each facade and designs an exterior wall structure. So we say that the double curtain wall is not a standard product but a form of passive use of climatic conditions.
This type of wall, which changes with the local climate, counteracts the changes in the surrounding environment of the building and ensures a relatively constant comfortable indoor environment. In this way, even in some extreme environmental conditions, the intervention of manual regulation systems is unavoidable, but energy consumption can be reduced in any case.
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