Research On Natural Ventilation Design Of Rural Housing In Yangtze Rive Delta

Since China’s reform and opening up, with the rapid economic development of village in Yangtze River delta, and the increasing of downtown dwellers’income, local residents’ expectations of rural housings are also increasing constantly. Meanwhile, because of the influence of urban housing, rural houses gradually approach to urban apartments in architectural form, function, energy use, and other aspects, the energy consumption of rural housing is increasing. Natural ventilation could take away indoor air pollution, promote indoor air quality and improve indoor thermal comfort degree without any increase in energy consumption. As a practical ecological technology, natural ventilation has always been played an important role in the residential construction. It should be more widely used in the area of Yangtze River delta, which has an excellent outdoor wind environment.As to the natural ventilation of rural housing of Yangtze River delta, this paper was mainly studied from the following aspects:1、It expounds the principle of natural ventilation theoretically, and then discusses the application of natural ventilation in residential buildings.This paper firstly expounds the principles of natural ventilation from the aspect of pressure ventilation and thermal pressure ventilation, as well as discusses the superiority of natural ventilation from the aspects of thermal comfort, cooling and energy-saving, residential health and so on. Then, it analyzes the application experience of natural ventilation in residential buildings from two aspects of traditional housing and modern residence.2、It studies and analyzes the present status of rural housing and its natural ventilation of Yangtze River.Based on the exposition of geographical climate and cultural economy of Yangtze River delta, it analyzes the regional wind environment and gets to know that the wind environment in Yangtze River delta is good, which is in the condition of using natural ventilation to achieve building energy efficiency. Then, it analyzes the present situation of rural housing from four aspects of construction mode, status of energy consumption, existing problems and development trend, it concludes that rural housing is mainly classified as six types of cluster distribution:band along river layout, radiant along river layout, freestyle along water layout, mass layout, determinant arrangement and intensive layout, and there are mainly five types of individual buildings ("-shape" building, "L-shape" building, "I-shape" housing, courtyard housing and housing with several many courtyards) through investigating a large number of sample cases of villages and town settlements.From the aspects of subjectivity and objectivity, this paper investigates the current situation of natural ventilation for rural housing. Through the interview and questionnaire inquire to the villages and towns inhabitants of Yangtze River delta, we get to know from subjective aspect that inhabitant’s satisfaction to indoor comfort degree is not high and it is necessary to strengthen natural ventilation. Depending on objective aspects of site tests to typical residence in Yangtze River delta, it concludes that river and roadway play the function of air inducing and wind guiding; yard and half open space as the transition of indoor and outdoor space effectively improve the indoor ventilation; modern residence is more flexible in the functional space layout so it has good natural ventilation in the interior of building, but it is easier to take outdoor heat to indoor in summer; the traditional residential housing uses courtyards with good effect of sunshade and heat insulation to improve ventilation, which has effectively enhanced the indoor comfort, but its layout which is closed to outside affects the access of coming wind in summer and transition seasons; consequently, the performance of natural ventilation of rural housing is to be further improved. On the basis of investigation and research, it summarizes the existing problems of natural ventilation of rural housing and finds the main factors that restricted the natural ventilation is irrationality of planning layout and individual design of rural housing. Then, it proposes the design requirements for natural ventilation of rural housing from the ventilation requirement of different seasons and the ventilation design of rural housing.3、It established the evaluation method about natural ventilation of rural housing in Yangtze River delta.Based on the analysis of the existing evaluation indexes and evaluation standards, with the combination of climate condition and the subjective feeling of rural residents in Yangtze River delta, it proposed the evaluation method of natural ventilation in rural housing in Yangtze River delta. Meanwhile, it introduced quantative evaluation index (calm zone ratio and comfort wind speed zone ratio) in evaluation method, which is convenient for comparison and analysis of building scheme. This paper evaluates outdoor wind environment from wind speed, wind speed amplification coefficient, outdoor comfort wind speed zone ratio, outdoor calm zone ratio and the pressure difference between the front and back of the building. It evaluates indoor wind environment from wind speed, age of air and indoor comfort wind speed zone ratio.4、It established the numerical simulation methods of natural ventilation which has precisely reliable result and quick calculating speed.On the basis of comparing and analyzing CFD software, it is optimized to select software (STAR-CCM+) which has accurate computation result, powerful gridding function, ample custom function and is easy to automatic running to carry out numerical simulation computation. Meanwhile, it expands the function of software, develops input condition calculation module (the profile of wind speed) and post-processing calculation module (wind speed amplification coefficient, comfort wind speed zone ratio, calm wind zone ratio, pressure difference, the age of air), and improves the applicability of the software to building wind environment simulation. By comparing the result of numerical simulation and wind tunnel test, it is prior to select turbulence model (realizable two-layer model of k-Epsilo) to use in the further research, which has accurate calculation result, and meanwhile combine the existing research result to determine the analytical condition of numerical simulation. Through the comparison with the field test data, it verifies the accuracy of numerical simulation calculation result.In the process of numerical stimulation, it decomposes job step, finds the same job step among different working conditions, makes use of "macros" of STAR CCM+ and records Java language program file in the same job step, where the file can be directly operated in subsequent calculations, the same job step can be automatically operated and the numerical simulation job is simplified.5、It concludes the design strategy of natural ventilation for rural housing on the aspect of group building layout.Based on analysis on the typical cases and relative design factors of group building, this paper sums up the natural ventilation design strategy of group building on the aspect of rural settlement location, group building’s layout, building orientation, building interval, building altitude, waterscape arrangement, distribution of open space, arrangement of plants, numerical simulation analysis and so on.Rural housing shall be arranged surrounded by water or along river. Group building shall choose determinant arrangement or band along river layout, radiant along river layout and freestyle along water layout.Partial cluster design shall use determinant arrangement, and try to avoid using intensive layout. It is necessary to avoid forming local building dense area, especially the first line of building on windward side shall not so dense so as not to stop coming wind flow into the inside of group building. The orientation of rural housing is between due south and south by east 22.5 degree, which has good sunlight and ventilation. Building interval shall be between 12 and 18 meters, and building density shall be 31% to 36%. Rural housing has excellent outdoor wind environment in summer and winter. The pattern of same building height layout is superior to high-low cross layout. The building with two floors has good outdoor wind environment. Waterscape shall be appropriately arranged in the Southeast, South and East of building. River shall not be arranged in parallel with the prevailing wind direction in summer. It is appropriate to select and match the variety, location and height of vegetation according to the change of season. The shape and area of open space shall be arranged according to the condition of group buildings so as to improve wind environment situation around buildings.6、It concludes the design strategy of natural ventilation of rural housing on the aspect of individual building layout.Based on analysis on the typical cases and relative design factors of individual buildings, this paper sums up the natural ventilation design strategy of individual building on the aspect of mode optimization, plane ventilation organization, vertical ventilation organization, the layout of window and door, auxiliary ventilation design method (patio, alleyway, ventilating tower, sun louver, wind deflector, roof ventilation, facade ventilation, tunnel ventilation and ventilation at night) and numerical simulation analysis.It applies the design method of setting balcony, opening inside patio and building shape crossing to optimize the ventilation gallery inside of building and improve the indoor wind environment on the basis of enriching building shape, It is easy to form cross-ventilation and taking use of natural wind in "--shape" building. The natural ventilation of "L-shape" building is in relevant with the direction of coming wind and the wing spread out by its plane. "I-shape" housing has narrow face width and large depth which is not conductive to indoor natural ventilation. But the ventilation gallery inside of building formed by its tunnel and patio has effectively improve the indoor wind environment. Courtyard housing closed to outside is hard to form cut-through air flue, and its natural ventilation is in bad effect. In building plane layout, it is necessary to optimize building plane depending on the situation of building site, appropriately arrange and create cut-through indoor air flue. It is better to form cross-ventilation in mainly used room in order to avoid forming calm wind zone. Based on horizontal ventilation, it is possible to connect cut-through space (stair hall, patio and ventilating tower) in vertical direction, form three-dimensional crossed ventilation gallery, and promote natural ventilation effect. Reasonable opening of window and door hole can form well indoor cut-through air flue to avoid the whole room has only one opening, to avoid direct connection between air intake and air outlet, and to avoid opening the air intake hole and air outlet hole on the same side of wall under pressure. The width of window shall be generally controlled between 1/3 and 2/3 of the room width. The area of window and door hole shall be controlled between 15% and 25% of the area of floor. It is suitable to choose the model and opening mode of window and door reasonably according to room type. According to the situation of housing, it is appropriate to take use of numerical simulation analysis method, prefer to select auxiliary ventilation design method and improve indoor natural ventilation.