C.K. Chau

Analysis of embodied energy use in the residential building of Hong Kong

Energy use in buildings accounts for nearly half of the total primary energy use in Hong Kong. Until now, studies have primarily focused on energy conservation in building operation, even though recent research has indicated that the embodied energy used in residential buildings could account for up to 40% of the life-cycle energy used in residential buildings. Accordingly, this paper presents a study on the energy embodied in the residential building envelope of Hong Kong. A model for estimating the intensities of the embodied and demolition energy for buildings has been developed. Two typical high-rise residential buildings, the Housing Authority Harmony 1 and the New Cruciform blocks, are analysed based on the developed model. The results of the analysis provide an insight into the embodied energy usage profile in residential buildings in Hong Kong. Energy embodied in steel and aluminium ranks as the first and second largest energy demand and may account for more than three-quarters of the total embodied energy use in a residential building envelope in Hong Kong. This reveals those building components with significant potential for reduction in embodied energy demand.

Factors affecting the implementation of green specifications in construction

Green specifications constitute one of the important elements in green construction. New sustainability requirements and changing priorities in construction management have spurred the emerging green specifications to a faster pace of development. A cross-sectional survey has been conducted in Hong Kong in 2007 to identify principal factors leading to the success of preparing green specifications. Based on extensive construction management literature, 20 variables concerning sustainable construction were summarized. Using the Mann-Whitney U-test, the subtle differences between stakeholders in specifying construction work have been detected even with the high consistency of the responses among the groups. Moreover, five independent factors for successful specification of green construction have been categorized by factor analysis. They are related to (1) green technology and techniques, (2) reliability and quality of specification, (3) leadership and responsibility, (4) stakeholder involvement, and (5) guide and benchmarking systems. Whilst the first and fourth factors are generally more important, different stakeholder groups have different emphases. The results of the survey have been validated against established principles.

Estimating the total exposure to air pollutants for different population age groups in Hong Kong

Given that Hong Kong is one of the most densely populated cities in the world, the exposure of the Hong Kong people is one of the interesting research areas. In this study, an indirect approach was used to estimate the exposure to nitrogen dioxide (NO2), respiratory dust (PM10) and carbon monoxide (CO) pollutants experienced by different age groups of people in Hong Kong. The average concentrations of the 20 major microenvironments obtained from our measurement survey data, together with the people activity pattern data obtained from 7-day recall questionnaires, were used to predict frequency distributions to exposure assessment. Our results showed that Hong Kong people spent more than 86% of their time indoors. Homes were shown to be the one of the major exposure sites to NO2, CO and PM10 for all age groups. Our results also indicate that the 24-h NO2 exposure for individuals, irrespective of age, spending more than 2 h in commuting daily, was observed to be exceeding the 24-h NO2 exposure standards. This study was one of the pioneering studies with valuable contribution for modeling the estimates of exposures to NO2, PM10 and CO of different age groups in Hong Kong.

Environmental management system vs green specifications: How do they complement each other in the construction industry?

Environmental Management System (EMS) has been one of the important tools for sustainable construction for around two decades. However, many issues concerning sustainable development have not been properly addressed, and there is a need for the introduction of green specifications to advance green performance in construction through contract management. This paper defines green specifications, identifies the reasons for adopting green specifications and highlights the environmental issues that may not be addressed by solely adopting EMS. It also presents the results of a recent survey of practitioners concerning their opinions towards green specifications and possible impacts arising from their adoption. From the results of the survey, a framework for developing green specifications is deemed valuable for the cities striving for sustainability. Interestingly, the level of acceptable changes brought about by green specifications as perceived by different industry stakeholders is found to be unrelated to whether they were from organizations implementing EMS or not.

Characteristics of bioaerosol profile in office buildings in Hong Kong

Abstract A series of bioaerosol measurements have been conducted at two typical offices in Hong Kong for both a 4-day and a weekly period. Both the investigated offices were installed with heating ventilation and air-conditioning (HVAC) systems coupling with air handling units and fan coil units. Measurements were performed starting from early morning by the Anderson N6 impactor. The primary objectives of these measurements were to determine the temporal concentration profile of bioaerosol inside office environments during office hours, and to determine the effects of air change rate on the concentration profile. The highest bacteria concentrations were recorded to be 2912 CFU/m3 at the early morning hours during the starting-up period of HVAC systems. The highest fungi concentrations were recorded to be 3852 CFU/m3 during the weekend mornings. The results of studies also revealed that the air change rate inside the office environment had less significant effects than filtration on airborne bioaerosols. The background fungi concentration was found to have strong correlation with the indoor relative humidity level provided that the relative humidity level could be maintained for a certain period of time. Of the sampled bacteria 80% were found to be gram positive, while the dominating genera of fungi was found to be Cladosporium and Penicillium.

On the study of the credit-weighting scale in a building environmental assessment scheme

A major strength of the voluntary building environmental assessment method is to encourage good environmental practice beyond the current industry practice. For a successful voluntary scheme, the credit scale must be attractive to investors and performance-based criteria should be used. However, most of the current schemes use a combination of prescriptive and performance-based criteria, and credits are allocated using subjective judgement, irrespective of cost and practical implications of attaining improved performances. This is pointed to the need to establish an incentive-crediting scheme, which is oriented towards performance-based scales having credits linked to cost and performance. In formulating the incentive-crediting scheme, the cost effectiveness of different energy-saving level in a base building is investigated under the premise that the investors would pursue a strategy in the most cost-effective manner. This paper presents a conceptual framework for policy makers to formulate an incentive-crediting scale for accrediting criteria within the greenhouse gas objectives of a building environmental assessment scheme in Hong Kong, aiming to attract participation of the profit-maximising investors. Establishment of an incentive-crediting scale starts from developing a carbon dioxide abatement curve for greenhouse gas emission. This is subsequently followed by dividing the maximum energy-saving potential into ten equal energy reduction intervals. The incentive-crediting scheme is formulated on a basis that proportionally more credits would be rewarded for diminishing investment return of consecutive reduction levels in a base building.

Can surrounding greenery reduce noise annoyance at home

Annoyance has been identified as the most important psychological impact arisen from noise. Besides socioeconomic status, residing neighborhood characteristics such as greenery has been shown to be able to reduce noise annoyance. To study the effects of these potential annoyance modifiers, nine hundred and ninety-two responses were collected through face-to-face interviews via questionnaire surveys. Among them, six-hundred and eighty-eight responses were collected together with adequate dwelling information which enabled a more accurate prediction of home noise levels. All these data were analyzed using an ordered logit model. Results indicate that greenery perception exerts considerable influence on noise annoyance rated at home. Wetland parks and garden parks are shown to be able to reduce noise annoyance to a greater degree than grassy hills. And the effects of the perceived amount of greenery on noise annoyance reduction at home differ according to the setting of greenery to which participant perceived from individual home.

A modeling investigation of the impact of street and building configurations on personal air pollutant exposure in isolated deep urban canyons

This study evaluated the effectiveness of different configurations for two building design elements, namely building permeability and setback, proposed for mitigating air pollutant exposure problems in isolated deep canyons by using an indirect exposure approach. The indirect approach predicted the exposures of three different population subgroups (i.e. pedestrians, shop vendors and residents) by multiplying the pollutant concentrations with the duration of exposure within a specific micro-environment. In this study, the pollutant concentrations for different configurations were predicted using a computational fluid dynamics model. The model was constructed based on the Reynolds-Averaged Navier-Stokes (RANS) equations with the standard k-ε turbulence model. Fifty-one canyon configurations with aspect ratios of 2, 4, 6 and different building permeability values (ratio of building spacing to the building façade length) or different types of building setback (recess of a high building from the road) were examined. The findings indicated that personal exposures of shop vendors were extremely high if they were present inside a canyon without any setback or separation between buildings and when the prevailing wind was perpendicular to the canyon axis. Building separation and building setbacks were effective in reducing personal air exposures in canyons with perpendicular wind, although their effectiveness varied with different configurations. Increasing the permeability value from 0 to 10% significantly lowered the personal exposures on the different population subgroups. Likewise, the personal exposures could also be reduced by the introduction of building setbacks despite their effects being strongly influenced by the aspect ratio of a canyon. Equivalent findings were observed if the reduction in the total development floor area (the total floor area permitted to be developed within a particular site area) was also considered. These findings were employed to formulate a hierarchy decision making model to guide the planning of deep canyons in high density urban cities.

Assessing the cost effectiveness of an environmental assessment scheme

Abstract This paper examines the key issues involved in evaluating cost and benefits of various accredited criteria of an environmental assessment scheme in Hong Kong. Economic benefit–cost ratios have been developed for various criteria to help the developers and designers to identify the economic impact and cost effectiveness of the accredited criteria. Results of this analysis reveal that the economic benefit–cost ratios vary among different credits, and 24 out of total 56 credits could provide potential economic benefit for the developers and designers. Accordingly, a decision strategy for prioritising the criteria selection has been developed for the developers and designers. Besides, the use of economic benefit–cost ratios for revising the weighting scale within the performance-specific criteria is discussed.

Towards a successful voluntary building environmental assessment scheme

Voluntary building assessment schemes have emerged worldwide to help assess the environmental performance of buildings. As building environmental assessment is a rapidly evolving field, the scope and details of such assessment schemes are continuously undergoing updating and refinement. Substantial efforts have been devoted to the design and improvement of the assessment schemes to make them capable of defining an objective building profile. Although most of the existing schemes are voluntary, many fail to encourage participation of the building investors and designers. In order to widen acceptance, the design of the scheme should be oriented towards the manner in which investors make decisions. This paper provides an overview of the vital elements and changes needed, so as to make a voluntary building environmental assessment scheme more attractive and successful, and will include reforms not only in the scope and the credit weighting philosophy but also in its nature.