K. W. Tham

K. W. Tham
National University of Singapore | NUS · Department of Building

PhD

About

202
Publications
75,191
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5,706
Citations

Publications

Publications (202)
Data
Series of research on thermal responses around AC system with ceiling fan in the tropics. AC system with fans has nice three features to improve thermal comfort, to reduce energy consumption of AC system and to reduce airborne infection risk.
Article
Full-text available
We evaluated diurnal trends of size-resolved indoor and outdoor fluorescent biological airborne particles (FBAPs) and their contributions to particulate matter (PM) within 0.5–20 μm. After a ten-week continuous sampling via two identical wideband integrated bioaerosol sensors, we found that both indoor and outdoor diurnal trends of PM were driven b...
Article
The utilization of physical dividers has been recommended as a practical approach to reducing the droplet and aerosol transmissions of the COVID‐19 virus (SARS‐CoV‐2). This study conducted a series of experiments using video recording with a high‐speed camera, particle image velocimetry (PIV) technique, and concentration measurements. The effective...
Article
Indoor airborne transmission largely depends on air distribution and ventilation. This study experimentally and numerically investigates steady-state aerosol transmission characteristics in a full-size room using a dedicated outdoor air system coupled with ceiling fans. Tracer gas was used to simulate the exhaled droplet nuclei from the infector, a...
Article
Several relationships between air temperature and work performance have been published. We reanalysed the one developed in 2006 by Seppänen et al.; which is probably the best known. We found that even when significant, its prediction accuracy is very low (R² = 0.05, MAE = 1.9%, RMSE = 3.1%). We consequently reviewed the literature and found 35 stud...
Article
Assessment of integrated personal exposure (PE) to airborne particulate matter (PM) across diverse microenvironments (MEs) over 24 h under different exposure scenarios is necessary to identify appropriate strategies to improve urban air quality and mitigate the health effects of PM. We carried out a collaborative study in a densely populated city-s...
Article
In a business as usual scenario, atmospheric carbon dioxide concentration (CO2) could reach 950 parts per million (ppm) by 2100. Indoor CO2 concentrations will rise consequently, given its dependence on atmospheric CO2 levels. If buildings are ventilated following current standards in 2100, indoor CO2 concentration could be over 1300 ppm, depending...
Article
Looking further than COVID-19, some of the key messages: 1. We from now on should include the risk of indoor respiratory infections in our design of buildings and its ventilation. 2. Treat the air quality in a similar way as we are used to for water and food quality. 3. ‘Visualize’ the air quality by displaying monitoring values (e.g. CO2 concentra...
Article
Full-text available
The combustion of fossil fuels is a significant source of particulate-bound black carbon (BC) in urban environments. The personal exposure (PE) of urban dwellers to BC and subsequent health impacts remain poorly understood due to a lack of observational data. In this study, we assessed and quantified the levels of PE to BC under two exposure scenar...
Article
Field surveys were carried out to evaluate the thermal comfort, perceived air quality (PAQ) of occupants and energy consumption in two different spaces of an actual university building, one of which is equipped with a Dedicated Outdoor Air System integrated with ceiling fans (DOAS-CF) and the other equipped with a conventional Fan Coil Unit (FCU)....
Article
The performance of a low‐cost fan filter unit (FFU) in mitigating hazardous particulate matter (PM) levels in a naturally ventilated school classroom is presented. The FFU can be considered as a simplified mechanical ventilation and air‐conditioning system without heating and cooling functions. The FFU improves indoor air quality through introducti...
Conference Paper
Full-text available
Thermal comfort assessment for the built environment has become more available to analysts and researchers due to the proliferation of sensors and subjective feedback methods. These data can be used for modeling comfort behavior to support design and operations towards energy efficiency and well-being. By nature, occupant subjective feedback is imb...
Article
Full-text available
Understanding occupants’ satisfaction with their environment is an important step to improve indoor environmental quality (IEQ). These satisfaction data are limited to Singaporean commercial buildings. We surveyed (N = 666) occupant satisfaction with 18 IEQ parameters in seven Green Mark certified air-conditioned commercial buildings in Singapore....
Conference Paper
Full-text available
Dedicated outdoor air system with ceiling fans (DOAS-CF) to achieve both indoor environment and energy savings at warm and humid conditions has attracted recent attention. The aim of this study is to investigate thermal comfort and perceived air quality (PAQ) in university classrooms employing a DOAS-CF at warm temperature setpoints. Field surveys...
Preprint
Full-text available
Thermal comfort assessment for the built environment has become more available to analysts and researchers due to the proliferation of sensors and subjective feedback methods. These data can be used for modeling comfort behavior to support design and operations towards energy efficiency and well-being. By nature, occupant subjective feedback is imb...
Article
Full-text available
During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and...
Conference Paper
Full-text available
Building ventilation standards use indoor carbon dioxide (CO2) levels as a proxy for air quality, acknowledging that at typical indoor levels, CO2 itself is not a pollutant. By 2100, outdoor CO2 levels may reach 900 ppm. With current ventilation standards, that would nearly double the levels of chronic, indoor CO2 exposure, raising concerns for its...
Conference Paper
Full-text available
A Dedicated Outdoor Air System in conjunction with ceiling fans (DOAS-CF) has attracted considerable attention in view of its potential for high energy-efficiency and is capable of enhancing indoor environmental quality in the tropics. The effects of furniture and posture on the cooling effect under DOAS-CF were investigated using thermal manikin i...
Article
The performance of a Dedicated Outdoor Air System integrated with ceiling fans (DOAS-CF) to enhance thermal comfort, perceived air quality (PAQ) and energy-saving potential was examined. 26 subjects were exposed to the combinations of temperatures (24, 27 and 30°C) and air velocities in the range of 0.07 to 1.87 m/s at relative humidity (RH) of 60%...
Conference Paper
Air conditioning and ventilation strategies in lecture rooms impact energy and indoor exposure with consequential effects on occupant satisfaction with the indoor environmental quality. Optimizing thermal comfort, ventilation effectiveness and energy efficient is challenging. Few field studies on the penalty of over ventilation or under ventilation...
Article
Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow charac...
Article
To date, exposure studies linking dust mite allergens with asthma and allergic morbidities have typically relied on sampling from representative locations in the home for exposure assessment. We determine the effects of differing microenvironments allergen exposures on asthma and asthma severity among 25 case and 31 control preschool children in Si...
Article
The effects of temperature, air movement and initial metabolic rate on transient thermal sensation at warm temperatures and high humidity among tropically acclimatized people were investigated. 26 tropically acclimatized subjects (13 males and 13 females) participated in the experiments with two different initial metabolic rates at temperatures of...
Article
Indoor environmental quality (IEQ) has become an important component of green building certification schemes. Whilst green buildings are expected to provide enhanced IEQ, higher occupant satisfaction, and less risks for occupant health when compared with non‐green buildings, literature suggests inconsistent evidence due to diverse research design,...
Preprint
Full-text available
Growth in Information and Communication Technology (ICT) has trigged an unprecedented proliferation of appliances a.k.a. Miscellaneous Electrical Loads (MELs) in buildings. Till now, managing MELs energy consumption in an optimum, cost-effective and intelligent manner in buildings remain an open-challenge. This article introduces a new supervised,...
Article
Background: Influenza is a common respiratory illness in Singapore, a densely populated tropical city. This study aims to decipher local transmission of influenza viruses via aerosols from human nasal droplets. As the circulating viruses are constantly undergoing antigenic changes, another objective is to construct phylogenetic trees based on the...
Conference Paper
Full-text available
Energy savings of the AC system is crucial in achieving energy conservation in buildings in tropical regions. A new hybrid AC system comprising outdoor air handling units operated in conjunction with ceiling fans aims to achieve energy saving due to raising room air tempera-ture and minimizing the air-conditioning requirements. However, the micro c...
Article
Energy savings of the Air-Conditioning (AC) system is crucial in achieving energy conservation in buildings in the tropical region. A Dedicated Outdoor Air System with ceiling fans (DOAS-CF) aims to achieve energy savings arising from elevated room air temperature and minimizing the air-conditioning requirements. The objective of this study is to i...
Article
Full-text available
Recognizing the value of open-source research databases in advancing the art and science of HVAC, in 2014 the ASHRAE Global Thermal Comfort Database II project was launched under the leadership of University of California at Berkeley's Center for the Built Environment and The University of Sydney's Indoor Environmental Quality (IEQ) Laboratory. The...
Article
Occupancy information is important to building facility managers in terms of building operation, predictive control, safety, as well as the indoor environment quality. Previous works have addressed different occupancy counting and estimation solutions in different buildings or spaces. In this study, we adopted a single system-single zone test bed u...
Article
Air conditioning and mechanical ventilation systems may be oversized in commercial buildings in the Tropics. Oversized cooling coils may lead to reduced dehumidifying performance, indoor air quality and thermal comfort and increased energy consumption. In this paper, an adaptable cooling coil design is assessed with a general-purpose coil selection...
Article
The effectiveness of a low energy fan-filter unit (FFU) in mitigating human exposure to airborne particulate matter (PM) during haze episodes in a naturally ventilated hostel room is presented. The study adopts a case-reference method by conducting a series of field tests in a test room equipped with FFU and in a reference room with no FFU. PM conc...
Article
Energy consumption and indoor environment quality (IEQ) of buildings have been linked to human occupants. Predicting the number of occupants in a space is essential for the effective management of various building operation functions as well as improve energy efficiency. This study is the first to compare the performance of physical and statistical...
Conference Paper
Full-text available
Occupancy information is important to building facility mangers in terms of predictive control, safety, as well as the indoor environment quality. Previous works have addressed different occupancy counting and estimation solutions in different buildings or spaces. In this study, we build up a test bed using the existing university lecture theatres...
Article
Full-text available
Retrofitting is widely explored as one of the energy conserving opportunities for existing buildings, in which both passive and active solutions are carefully evaluated. However, when different retrofitting solutions are combined and applied to a building, the total energy savings potential, which is less than the sum of the savings from applying t...
Article
Clustering algorithms have been successfully applied in analyzing building energy consumption data. It has proven to be an effective technique to identify representative energy consumption patterns as well as being a pre-processing step for other techniques. In this paper, we propose a clustering method based on k-Shape algorithm, which is a relati...
Article
A reflective approach is adopted in analyzing the reviews on the impact of indoor air quality on humans over the last 30 years (1986–2016). The major findings reiterate the concerns of indoor air pollution (IAP) and provide a deeper understanding of how contaminants contribute to, and interact to accentuate the adverse effects on humans. Issues whi...
Conference Paper
Full-text available
Smart building energy management requires knowledge of individual appliance operation from reduced metering points. The key purpose of this study is to present a classification framework for offices that can help discover individual appliances and its operational modes from single-point aggregate measurements. This approach to non-intrusive load mo...
Article
Full-text available
High temperature cooling is gaining more attention in commercial buildings of the tropical climates where temperature and humidity is high all year round. In this air-water system, radiant-convective cooling is provided into conditioned space through using higher chilled water temperature compared to conventional all air system. Radiant cooling pan...
Conference Paper
Full-text available
Practical energy auditing in offices poses several challenges unlike homes e.g. physically large space, diverse energy appliances types, several appliance instances and occupancy non-obstructiveness. However, improved energy-auditing measures using predictive analytics can benefit energy savings and reduce building operational costs. A review of so...
Article
From two independent research studies conducted to understand effect of varying thermal and indoor air pollution exposures on non-asthmatics and asthmatics' responses and work performances, this paper attempts to answer the question: Towards whom should IEQ control be sympathetic - asthmatics or non-asthmatics? The studies were conducted in a 240 m...
Conference Paper
Full-text available
Low exergy concept can be implemented in air conditioning system of the tropical buildings through a reduction of the difference between operational temperature of cooling system and indoor space whilst meeting thermal comfort requirements. Decentralized dedicated outdoor air system (DDOAS) coupled with radiant cooling system (RCS) are low exergy d...
Article
Full-text available
This study investigates the ability of human convective boundary layer (CBL) to transport the pollution in a quiescent indoor environment. The impact of the source location in the vicinity of a human body is examined in relation to pollution distribution in the breathing zone and the thickness of the pollution boundary layer (PBL). The study, in ad...
Article
Unlabelled: The inhalation intake fraction was used as an indicator to compare effects of desktop personalized ventilation and mixing ventilation on personal exposure to directly released simulated cough droplets. A cough machine was used to simulate cough release from the front, back, and side of a thermal manikin at distances between 1 and 4 m....
Article
The Building and Construction Authority Green Mark Scheme in Singapore encourages better indoor environmental quality for healthier workplaces for occupants. However, studies have shown that green buildings do not necessary ensure better indoor environmental quality. This case study aimed to compare the prevalence of sick building syndrome symptoms...
Article
The deployment of low exergy concepts in buildings, which promotes high temperature cooling HVAC systems introduces alternative solutions in the tropical climate. This study evaluates the performance of a decentralized dedicated outdoor air system combined with a radiant cooling system (decentralized DOAS-RCS) in terms of occupant thermal comfort a...
Article
Unlabelled: The effects of the human convective boundary layer (CBL), room airflow patterns, and their velocities on personal exposure are examined. Two pollutants are studied which simulate particles released from the feet and generated at distances of 2 and 3 m by a human cough. A thermal manikin whose body shape, size, and surface temperatures...
Conference Paper
Full-text available
The commercial sector is responsible in a large degree for the overall energy consumption around the world and Information and Communication Technologies (ICT) constitute an important category of electricity loads which is becoming dominant in offices. Recognizing the importance of using ICT equipment more rationally for saving energy in commercial...
Article
Full-text available
Two independent studies by two separate research teams (from Hong Kong and Singapore) failed to detect any influenza RNA landing on, or inhaled by, a life-like, human manikin target, after exposure to naturally influenza-infected volunteers. For the Hong Kong experiments, 9 influenza-infected volunteers were recruited to breathe, talk/count and cou...
Article
The impact of asthma, exposure period and filter condition downstream of the mixing box of air-conditioning system on building occupants’ perceptual response, work performance and salivary α-amylase secretion during exposures to ozone and its initiated chemistry products is studied. The experiments were conducted in a Field Environmental Chamber “F...
Conference Paper
Full-text available
The basic principle of low exergy building systems is the minimization of excess temperature gradients across building systems so that the quality of the energy supplied to the building better matches with the actual demand of the building. Several low exergy technologies which were developed at ETH, Switzerland were implemented in a small research...
Article
Full-text available
This paper presents the current state of the art regarding work performed related to the electric energy consumption for Information and Communication Technologies (ICTs) and Miscellaneous Electric Loads (MELs), in office and commercial buildings. Techniques used for measuring the energy consumption of office plug loads, and efforts for saving ener...
Article
Full-text available
This study aims to characterize human convective boundary layer (CBL) in a quiescent indoor environment. The study has two objectives: first, to characterize the velocity field around the thermal manikin under two ambient temperatures and body postures; and secondly, the influence of clothing insulation/design, chair design, table positioning and s...
Article
This study investigates the interaction between the human convective boundary layer (CBL) and uniform airflow with different velocity and from different directions. Human body is resembled by a thermal manikin with complex body shape and surface temperature distribution as the skin temperature of an average person. Particle image velocimetry (PIV)...