Natural ventilation can be used as a low-cost alternative to mechanical ventilation. Bearing in m... more Natural ventilation can be used as a low-cost alternative to mechanical ventilation. Bearing in mind that ventilation mode plays an important role in natural ventilation performance, the current study investigates the effectiveness of two major natural ventilation modes (i.e. single-sided and cross ventilation) in providing thermal comfort for occupants of high-rise residential buildings in cooling dominant climates. Measurements of air velocity, temperature and relative humidity were carried out in a unit located in a high-rise residential building in Brisbane, Australia. Both single-sided and cross ventilation settings were examined in two consecutive days in summer. The extended Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfaction (PPD) were calculated and results showed a considerably better performance of cross ventilation over single-sided ventilation. Cross ventilation could provide thermal comfort in a typical hot summer day for most of the day (greater than 70% of the time), while, for single-sided ventilation the thermal conditions of internal spaces was comfortable for only 1% of the time.
For the design of naturally ventilated buildings, information of air speed at the openings of a b... more For the design of naturally ventilated buildings, information of air speed at the openings of a building is important. However, the only data set usually available to designers is meteorological data, such as wind speed and direction measured at weather stations. This paper explores the ratio of air speed at building openings to the wind speed measured at weather stations. Meteorological data from three weather stations as well as air velocity that was obtained through full-scale physical measurements were used in this study. The results showed that air speed at building openings was about half of the wind speed recorded at the closest station to the case study. This ratio reduced to approximately 30% when comparing to the weather stations located in greater distance and more open areas. Given that air speed at the openings has a direct relation to the ventilation rate, employing these ratios to the available weather data when designing for natural ventilation, can provide more realistic picture of natural ventilation performance.
Balconies, as one of the main architectural features in subtropical climates, are assumed to enha... more Balconies, as one of the main architectural features in subtropical climates, are assumed to enhance the ventilation performance of buildings by redirecting the wind. Although there are some studies on the effect of balconies on natural ventilation inside buildings, the majority have been conducted on single zone buildings with simple geometries. The purpose of this study is to explore the effect of balconies on the internal air flow pattern and ventilation performance of multi-storey residential buildings with internal partitions. To this end, a sample residential unit was selected for investigation and three different conditions tested, base case (no balcony), an open balcony and a semi-enclosed balcony. Computational Fluid Dynamics is used as an analysis method due to its accuracy and ability to provide detailed results. The cases are analysed in terms of average velocity, flow uniformity and number of Air Changes per Hour (ACH). The results suggest the introduction of a semi-enclosed balcony into high-rise dwellings improves the average velocity and flow uniformity. Integrating an open balcony results in reduction of the aforementioned parameters at 0° wind incidence.
Complex behavior of air flow in the buildings makes it difficult to predict. Consequently, archit... more Complex behavior of air flow in the buildings makes it difficult to predict. Consequently, architects use common strategies for designing buildings with adequate natural ventilation. However, each climate needs specific strategies and there are not many heuristics for subtropical climate in literature. Furthermore, most of these common strategies are based on low-rise buildings and their performance for high-rise buildings might be different due to the increase of the wind speed with increase in the height. This study uses Computational Fluid Dynamics (CFD) to evaluate these rules of thumb for natural ventilation for multi-residential buildings in subtropical climate. Four design proposals for multi-residential towers with natural venti-lation which were produced in intensive two days charrette were evaluated using CFD. The results show that all the buildings reach acceptable level of wind speed in living areas and poor amount of air flow in sleeping areas.
Natural ventilation can be used as a low-cost alternative to mechanical ventilation. Bearing in m... more Natural ventilation can be used as a low-cost alternative to mechanical ventilation. Bearing in mind that ventilation mode plays an important role in natural ventilation performance, the current study investigates the effectiveness of two major natural ventilation modes (i.e. single-sided and cross ventilation) in providing thermal comfort for occupants of high-rise residential buildings in cooling dominant climates. Measurements of air velocity, temperature and relative humidity were carried out in a unit located in a high-rise residential building in Brisbane, Australia. Both single-sided and cross ventilation settings were examined in two consecutive days in summer. The extended Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfaction (PPD) were calculated and results showed a considerably better performance of cross ventilation over single-sided ventilation. Cross ventilation could provide thermal comfort in a typical hot summer day for most of the day (greater than 70% of the time), while, for single-sided ventilation the thermal conditions of internal spaces was comfortable for only 1% of the time.
For the design of naturally ventilated buildings, information of air speed at the openings of a b... more For the design of naturally ventilated buildings, information of air speed at the openings of a building is important. However, the only data set usually available to designers is meteorological data, such as wind speed and direction measured at weather stations. This paper explores the ratio of air speed at building openings to the wind speed measured at weather stations. Meteorological data from three weather stations as well as air velocity that was obtained through full-scale physical measurements were used in this study. The results showed that air speed at building openings was about half of the wind speed recorded at the closest station to the case study. This ratio reduced to approximately 30% when comparing to the weather stations located in greater distance and more open areas. Given that air speed at the openings has a direct relation to the ventilation rate, employing these ratios to the available weather data when designing for natural ventilation, can provide more realistic picture of natural ventilation performance.
Balconies, as one of the main architectural features in subtropical climates, are assumed to enha... more Balconies, as one of the main architectural features in subtropical climates, are assumed to enhance the ventilation performance of buildings by redirecting the wind. Although there are some studies on the effect of balconies on natural ventilation inside buildings, the majority have been conducted on single zone buildings with simple geometries. The purpose of this study is to explore the effect of balconies on the internal air flow pattern and ventilation performance of multi-storey residential buildings with internal partitions. To this end, a sample residential unit was selected for investigation and three different conditions tested, base case (no balcony), an open balcony and a semi-enclosed balcony. Computational Fluid Dynamics is used as an analysis method due to its accuracy and ability to provide detailed results. The cases are analysed in terms of average velocity, flow uniformity and number of Air Changes per Hour (ACH). The results suggest the introduction of a semi-enclosed balcony into high-rise dwellings improves the average velocity and flow uniformity. Integrating an open balcony results in reduction of the aforementioned parameters at 0° wind incidence.
Complex behavior of air flow in the buildings makes it difficult to predict. Consequently, archit... more Complex behavior of air flow in the buildings makes it difficult to predict. Consequently, architects use common strategies for designing buildings with adequate natural ventilation. However, each climate needs specific strategies and there are not many heuristics for subtropical climate in literature. Furthermore, most of these common strategies are based on low-rise buildings and their performance for high-rise buildings might be different due to the increase of the wind speed with increase in the height. This study uses Computational Fluid Dynamics (CFD) to evaluate these rules of thumb for natural ventilation for multi-residential buildings in subtropical climate. Four design proposals for multi-residential towers with natural venti-lation which were produced in intensive two days charrette were evaluated using CFD. The results show that all the buildings reach acceptable level of wind speed in living areas and poor amount of air flow in sleeping areas.
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Papers by Sara Omrani