Ventilation design for high-rise residential buildings : building regulation and required innovation

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Ventilation design for high-rise residential buildings : building regulation and required innovation

 

Author: Lau, Pak-kai
Title: Ventilation design for high-rise residential buildings : building regulation and required innovation
Degree: M.Eng.
Year: 2007
Subject: Hong Kong Polytechnic University -- Dissertations.
High-rise apartment buildings -- Heating and ventilation -- China -- Hong Kong.
Ventilation -- Design.
Department: Dept. of Building Services Engineering
Pages: x, 119 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2117576
URI: http://theses.lib.polyu.edu.hk/handle/200/175
Abstract: As the economics grow rapidly in the world, the building industry develops fast as well. The high quality residential building, regarding to the health issues, becomes more and more demanding. Focused research on the health risks of indoor air pollution began from the middle of 1960s. Some of the early research focused on the risks to respiratory health posed by smoking indoors. Since the incident of outbreak of Asian Flu in HK in 2001 and world-wide scale outbreak of SARS in 2003, the high risk of aerosol transmitted infectious diseases makes the issue - cross contamination be more significant. During the SARS outbreak in the spring of 2003 in Hong Kong, the vertical transmission pattern in high-rise residential buildings was observed. With respect to infectious disease control, this inter-flat or inter-zonal flow becomes a serious issue. The ventilation standards on both the international level and local level were reviewed. ASHRAE standards were chosen to demonstrate the ventilation standards on the international level. The review showed that there is insufficient guidance on the ventilation design requirements in high-rise residential buildings with respects to cross contamination. In Hong Kong, the ventilation design requirements are rather simple than that one in ASHEAE. The conclusion was that there are not sufficient regulations concern cross contamination led by ventilation yet. There were two kinds of ventilation: natural ventilation and mechanical ventilation. In the general case, the natural ventilation was applied in the high-rise residential building. In the natural ventilation, there were two main driving forces: wind forces (by pressure difference) and buoyancy forces (by stack effect) which can appear simultaneously, but there must only be one force dominating the ventilation of the buildings. In other words, ventilation rate at low wind speeds is dominated by the stack effect. As the wind speed increases, wind dominated ventilation takes over. From the results, it was found that the wind speeds obtained by HKO were overestimated. Due to the presence of other buildings or similar large obstructions in close proximity, the actual wind speed data should be far less than that obtained from HKO. For those wind speed data obtained from real site measurements, it revealed that the wind speeds were at the low level as 0.2m/s in most of the time. Besides, it was found that the higher wind speed suppressed the value of re-entry ration (k) and mass fraction (M). Vice versa, the lower wind speed led to a higher value of & and M Apparently, the higher value of k & Mat the low wind conditions are indications of higher risks of airborne infectious disease spreading from the lower floor residents to the upper floor residents. Results also discovered that the M increase with the increase of indoor-outdoor temperature differences which means with the larger indoor-outdoor temperature difference, there was with the higher risks of airborne infectious disease spread from the lower floor to the upper floor. In this study, the maximum mass fraction A/was found to be about 0.28, which means that the air near the window upstairs contains 28% of the exhaust air originating from the lower room. In the current ASHRAE ventilation standard, the dilution factor should exceed the value 50 to 1 when highly hazardous pollutants are involved, which is correspond to the mass fraction 0.02 (ASHRAE 2004). The results showed that the ventilation of these flats do not meet the standard. In this paper, it pointed out the effects of air flow pattern or the transmission pattern of contaminants on different architectural design, such as overhangs between two floors, different floor to floor height, and different environment, nearby physical environment of the building, different wind direction around the building need further study, and the Anemometer was recommended to be applied in the further study.

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