Study On The Air Environment Characteristics Of The Indoor And Outdoor Space Of Enclosed Buildings

A courtyard form, i.e. one enclosed building, is a very common architectural pattern throughout many periods of history. Its enclosed space has been thought to offer great potential for utilizing natural ventilation and creating a relatively independent outdoor microclimate. The courtyard form is widely used by modern unban building structures. Many public buildings contain some form of courtyard, often as a central core circulation space. It has been developed during the last periods through the process of trial and error to a general climatic satisfying state within the available resources. In northern climates courtyards are used as wind shelters and sun-traps and in southern climates for shelter from the sun and the reduction of courtyard and indoor mean temperatures.Nevertheless, some key issues on whether the energy saving effect of an enclosed building can be sufficiently utilized are still unknown. For example, whether the natural ventilation advantage of an enclosed building will lead to excessive room ventilation heat loss in the cold northern climate, whether an enclosed building is effective enough to remove the internal pollutant while providing a good microclimate in the courtyard for people’ outdoor activities. Therefore, in this paper, field measurements and numerical simulations on the air environment characteristics of the indoor and outdoor spaces of enclosed buildings were conducted, and the indoor and outdoor air environment characteristics for the non-enclosed building form (i.e. the regularly aligned building layout) were also investigated.Field measurement and questionnaire survey on the indoor air quality and thermal comfort in high occupant density dormitory buildings, which are non-enclosed buildings, were firstly conducted in winter and in summer. Then, the indoor air environment of enclosed buildings and non-enclosed buildings were tested simultaneously for comparison. The results show that the room ventilation of an enclosed building is greater than that of a non-enclosed building under the same outdoor climate conditions. It reduces the utilization of solar radiation for an unheated room of an enclosed building, resulting in that though the indoor air temperature of a high occupant density room is low, the indoor air quality of such a room is improved.The air environment in courtyards with different enclosing forms were investigated. The results show that the cold and warm air infiltration from an air-conditioned room of an enclosed building in summer and winter, respectively, has significant impact on the ventilation and air environment of the courtyard. Particularly, even under the calm wind conditions, the courtyard ventilation induced by thermal forces when the building is heated is approximately equivalent to that induced by wind forces when the ambient wind speed is4.5～5.9m/s, and is effective enough to prevent the pollutant retention and accumulation in the courtyard. Meanwhile, the air temperature in the courtyard is higher than the ambient air temperature, thus the building envelope heat loss of the tested courtyard building is reduced by11%～20%. In addition, the effect of natural ventilation on the thermal environment in the courtyard depends on the conditions of solar radiation and opening/closing of the windows. The thermal comfort in the courtyard can be effectively improved if the windows are opened suitably.Based on the structural characteristics of an enclosed building, the steady and unsteady air flow and pollutant concentration distribution in a courtyard were numerically simulated to explore its fundamental features, and that for a regularly aligned building layout was also calculated for providing a baseline for comparison. The effect of the enclosed building layout on the pollutant dispersion under different wind directions was analyzed. The results show that the pollutant concentration in the vicinity of an enclosed building is higher than that for a regularly aligned building when the pollutant source keeps emitting, however, the pollutant concentration of the former decays rapidly while the pollutant concentration for the latter decays slowly when the pollutant stops emitting. Different from a regularly aligned building, the pollutant concentration in the courtyard of an enclosed building is not sensitive to the ambient wind directions.Under steady-state conditions, the pollutant removal capability of the lower zone of the courtyard is almost equivalent to that of a regularly aligned building layout, and the pollutant removal capability of the upper zone of the courtyard is more effective than that of a regularly aligned building layout. Lowering the opening height of the courtyard entrance only have a minimal impact on the air quality within the space below the height of2m in the courtyard. Reducing the opening area of the courtyard entrance is beneficial to the independence of the courtyard microclimate, thus a courtyard with a lower entrance opening height can interact with the local climate better than a courtyard with a higher entrance opening height. This method offers the potential for mitigating the contradictory ventilation demands on the independence of the courtyard microclimate and the air quality in the courtyard. Meanwhile, the height of the windward opening seems to have no substantial impact on the extent of the pollutant concentration in the courtyard increases with the increased building height.