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High-rise housing, a trend in densely populated cities around the world, increases energy use for water supply and corresponding greenhouse gas emissions. This paper presents an energy efficiency evaluation measure for water supply system designs and a mathematical model for optimizing pumping energy through the arrangement of water tanks in a building. To demonstrate that the model is useful for establishing optimal design solutions that integrate energy consumption into urban water planning processes which cater to various building demands and usage patterns, measurement data of 22 high-rise residential buildings in Hong Kong are employed. The results show the energy efficiency of many existing high-rise water supply systems is about 0.25 and can be improved to 0.26-0.37 via water storage tank relocations. The corresponding annual electricity that can be saved is 160-410 TJ, a 0.1-0.3% of the total annual electricity consumption in Hong Kong.

Occupant-generated carbon dioxide (CO2) is used as the tracer gas to determine ventilation rate. Although CO2 concentration may not provide a comprehensive indication of indoor air quality (IAQ), it can be a good indicator of the concentration of other human bioeffluents perceived as a nuisance and be used to identify the acceptability of IAQ in a space by its occupants. In this study, the acceptability of IAQ in air-conditioned offices was evaluated by the subjective responses of the office occupants with respect to indoor CO2 concentration. CO2 concentrations at 396 sample locations were measured and subjective responses at those locations were recorded by an electronic questionnaire. Specifically, an occupant’s indirect acceptability of the perceived IAQ indicated on a semantic differential evaluation scale was correlated to the occupant’s direct acceptability described by a dichotomous scale. The overall acceptability of IAQ from all occupants was then described by a logistic regression model and shown to correlate with indoor CO2 concentration.

Long-term measurement results of indoor air quality (IAQ) over a general community can be used to evaluate the effectiveness of mitigation measures for IAQ improvement of premises. However, this approach requires considerable measurement efforts and thus the complete data sets are not available in many circumstances. This study proposes an epistemic approach in estimating the probable influences of an IAQ policy for Hong Kong offices, using the regional IAQ measurement databases results of IAQ in offices were collected and were used to quantify the IAQ improvement for Hong Kong offices. It is noted that IAQ dissatisfaction due to air pollutants predominated by indoor emissions of volatile organic compounds (VOCs) might need additional attentions for an effective IAQ improvement programme. Practical application: This study provides updated information on the forecasts of IAQ in air-conditioned offices of Hong Kong due to the influence of the IAQ policy implemented in 1997-1999. It is a useful source of reference for policymakers and decision makers in evaluating an indoor air pollution control policy for air-conditioned offices.

In practice, the drag coefficient of a particle is usually calculated using empirical relationships obtained by generalizing experimental data. This study demonstrates that using the default Stokes’ law settings in FLUENT to computationally predict the drag coefficients for bioaerosol deposition is not really appropriate: the average fractional bias is 7% and the average normalized mean square error is 15%. Comparatively, the errors for bacteria (−12% to 24%) are larger than those for fungi (−8% to 26%). These errors, however, can be minimized by selecting a suitable drag constant, which can be determined based on the bioaerosol diameter. The average drag constants for bacteria were shown by the results to vary from 0.25 to 3.1, which are much smaller than the default value of 24, whereas the values for fungi were generally larger and in a wider range. This study also investigated the correlation between the drag coefficient and Reynolds number for common indoor bioaerosols with diameters between 0.69 and 8.6 µm. The outcome of this study would therefore provide a good reference point for future estimation of the deposition distribution patterns of various common indoor bioaerosols.

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Instantaneous flow rate estimation is essential for sizing pipes and other components of water systems in buildings. Although various demand models have been developed in line with design and technology trends, most water supply system designs are routinely and substantially over-sized to keep failure risks to a minimum. Three major types of demand models from the literature are reviewed in this paper: (1) deterministic approach; (2) probabilistic approach; and (3) demand time-series approach. As findings show some widely used model estimates are much larger than the field measurements, this paper proposes a Bayesian approach to bridge the gap between model-based and field-measured values for the probable maximum simultaneous water demand. The proposed approach is flexible to adopt estimates as its prior values from a wide range of existing water demand models for determining the Bayesian coefficients for reference models, codes, and design standards with relevant measurement data. The approach provides a useful method not only for evaluating the corresponding demand values from various design references, but also for responding to the call for sustainable building design.

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