Indoor and Built Environment

Air dehumidification plays an important role in improving air quality and maintaining thermal comfort. Increasing attention is paid to the membrane-based technology, which is based on water vapour transmembrane transport driven by mass transfer potential, together with sensible heat transfer under temperature difference. Membrane-based air dehumidification has been applied in heating, ventilation and air conditioning, compressed air dehumidification and environmental control in space vehicle, and some other engineering fields. This paper summarizes recent research results in these fields, including fundamental principles, membrane materials, membrane module structures, operation conditions and theory models. In the end, two methods of membrane-based dehumidification performance evaluation are introduced from perspective of energy and exergy, respectively.

The article presents the results of a laboratory study conducted at Shanghai Tongji University. The study compares participants’ mood and task performance between naturally-lit and artificially-lit environments, with a view to identify negative impacts, such as lighting variation and temperature asymmetry caused by dynamic natural light. It was observed that the mood change in the naturally-lit environment was more significant, especially the decrease of positive mood, than in the artificially-lit environment. For the subjects in the naturally-lit environment, performance scores decreased with increase in the light intensity and temperature asymmetry. Based on the study results, suitable daylighting design was recommended for classrooms or offices.

Blinds are a common type of shading device and are increasingly operated automatically to overcome the limitations of manual operation. Automated blinds need to be controlled to maximize benefits of incoming daylight (sunlight and skylight) and solar irradiance for enhancing occupant comfort and reducing energy consumption. However, most previous control methods focused on minimizing the negative impacts of daylight, and so failed to maximize the positive impacts of daylight and solar heat gain. Furthermore, all of previous blind control methods never consider the impact of adjacent buildings. The rates of sunlight, skylight and solar irradiance to indoor are fluctuated by the disturbance of solar access, which can cause visual discomfort of occupants such as glare and have an effect on energy consumption due to variations of heating or cooling load. The objective of this paper is to propose the automated blind control strategy considering adjacent buildings’ geometry in order to minimize the occupants’ discomfort from glare and to maximize daylight inlet and solar heat gain, which can contribute to reducing energy consumption in a building. The proposed strategy was evaluated and verified through the computer simulations and analysis of results.

Following the discovery of high levels of indoor radon in various parts of the world, every environmental protection agency is determined to address the potential radon problem. In India, many research groups are determined to characterize the problem as it might exist in Indian dwellings, where poor ventilation and mud structures are common. Not only radon but also its progeny are radioactive. Being a gas radon can disperse and its progeny can attach to aerosols/dust particles to be transmitted in indoor environments. Radon is the second leading cause of lung cancer in North America and the leading cause of lung cancer for individuals who have never smoked. Due to potential public health implications of exposure to high levels of radon, the characterization of radon problem in India must also be complemented with the development of a program to educate the public regarding radon. This paper is an attempt to provide awareness about the environmental radon, its origin, health concerns, present status of radon concentrations in dwellings of Northern India and some remedial actions for protection from radiation. The estimated indoor radon levels are looked into as recommended by the International Commission on Radiological Protection, 2009.

This research analysed the effect of the ecological material yellow soil (hwang-toh) on indoor environments. To accomplish this, two full-scale mock-ups were constructed: one with PVC-foamed wallpaper, which is generally used for indoor finishing, and the other with hwang-toh, which is an ecological material for wall finishing. Comparison and performance evaluations were conducted, and the effects of hwang-toh finishing on an indoor environment were verified. Through this research, it was confirmed that a hwang-toh plaster finish is effective in maintaining the comfort humidity of an indoor environment.

This study conducted a series of experiments on the airflow characteristics of one-side confined jets from a parallel-flow outlet with a two-tier perforated plate and a honeycomb in a push–pull ventilation system. Maximum velocity, maximum temperature and airflow trajectory were analysed and compared with previous studies about different outlets. The results showed that the dimensionless turbulence coefficient of the parallel-flow outlet was smaller than either the cased axial fan with open grille’s or the swirl diffuser’s turbulence coefficients from isothermal condition. Different development laws for the parallel-flow outlet discharging a hot air jet (Ar₀ = 0.024) on the floor were put forward. Furthermore, it was found that the velocity decay rate of the hot air jets with a parallel-flow outlet on the floor was slower than with the circular aperture over a flat surface. When Ar₀ ranged from 0.024 to 0.044, a semi-empirical equation was established to describe the trajectory of the hot jets from a parallel-flow outlet in a push–pull ventilation system. In addition, the baffle height of the suction outlet could be determined and corrected appropriately.

The aerodynamic effects of human movement can significantly influence the airflow motion and contaminants transmission in enclosed environments such as in aircraft cabins, cinema and conference room, and so it is necessary and important to study the characteristics of these aerodynamic effects. This work focuses on the aerodynamic characteristics of human movement behaviours including limbs pendulum and body motion. A thermal manikin is used in the corresponding environments to simulate these behaviours. The step frequencies of 20, 30, 40, 50 and 60 double steps per minute for limbs pendulum and the moving speeds of 0.5, 0.75, 1.0, 1.25 and 1.5 m/s for body motion are investigated in the experiments. In each case, the velocity distribution around the human body is measured by using hot-wire anemometers. The experimental results show that the characteristics of the velocity distribution induced by limbs pendulum depend on pendulum frequency and spatial location, and for body motion, it depends on moving speed, moving distance and spatial location. The analysis results show that body motion has a significant influence on the flow field, and its aerodynamic effects are greater than those due to limbs pendulum. When a human moves, more detailed profile of the human body leads to more complicated flow field in the nearby area.

This paper deals with analysing the thermal comfort performance of apartment units in a typical hot, dry climatic region, through real-time monitoring and dynamic simulation adopting Environmental Systems Performance – research (ESP-r) thermal simulation software. Real-time monitoring of thermal comfort parameters was carried out in representative units for a period of six months between January and June (winter to summer). The measured data were analysed and used to validate the simulated results obtained from the ESP-r model, which was subsequently used to establish the prevailing comfort characteristics and the thermal comfort response of the residential units. Thermal comfort predictions through Fanger’s expected Predicted Mean Vote (ePMV), Tropical Summer Index (TSI) and comfort temperature (T_comf) exhibited a significant variation. During summer, ePMV and T_comf estimated higher amount of heat discomfort (50% and 62%, respectively) compared to TSI index, which estimated 76% tolerable conditions when an air velocity of 1 m/s is available. During winter, TSI index indicated the prevalence of higher cold discomfort compared to the other indices. The results obtained have been used to develop predictive formulae for assessing thermal comfort for this building type, which can be used to arrive at quick thermal comfort estimates for any proposed design in a similar context.

Investigation of occupant’s indoor environment influences can be identified through perceptive-cognitive aspects. Such an investigation leads to affective responses such as satisfied or dissatisfied, annoyed or not annoyed and hot or cold. This study investigates the perceptive-cognitive aspects of indoor environment among students who are staying in multi-storey accommodations in Klang Valley area, Malaysia. The students were asked to participate in the subjective survey in order to gather their indoor environment satisfaction votes. The objectives of this study are (1) to know how does the occupant of naturally ventilated multi-storey student accommodations respond to their indoor comfort whilst staying in an uncontrollable indoor atmosphere and (2) to identify what are the design features that contribute to the achievement of occupant’s overall indoor environment satisfaction. The main findings suggest that the uncontrollable indoor condition which occurred when occupants open their windows resulted in a more significant dissatisfaction vote toward indoor noise level in conjunction with warmer thermal sensation incidences. Moreover, despite the increasing indoor noise level recorded in rooms at higher floor levels, the findings show that room location, room orientation and shading ratio are not considered to influence the occupants’ overall indoor environment satisfaction and dissatisfaction.

This article presents an integral approach to sustainable noise control system design for building ventilation systems in Hong Kong. This approach combines the analytic hierarchy process and life cycle analysis (LCA) to obtain a holistic view of the system performance in terms of human, economic, and environmental impacts. The approach was applied to the evaluation of various noise control systems including duct liners, silencers, semi-active noise control, and active noise control for ventilation systems. Although passive systems such as duct liners and silencers seem to consume more material resources than semi-active and active systems, the latter require sensors, controllers, resonators or loudspeakers, and electricity. In fact, the LCA showed little difference between the semi-active and active systems and the passive systems in term of resource depletion and carbon emission. As human impact and economic impact dominated the experts’ views on sustainability, the analysed results indicated that the most sustainable design was duct liners, followed by silencers, active noise control, and semi-active noise control.

TiO₂-supported precious metal photo- (PCO) and thermal catalytic oxidation (TCO) are new kind of formaldehyde degradation air cleaning methods, characterized to have low energy consumption for operation in air conditioning system and would produce no harmful by-products. In this study, Pt-TiO₂ thermal catalyst was prepared and its composition and pore structure was examined by X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) methods. The impact of reaction temperature, air-flow rate and initial concentration of formaldehyde to the catalytic degradation effect was investigated. The largest relative change rate of the specific degradation rate was 0.49%/℃ within the temperature range from 70 to 120℃. Compared with other relevant studies, the reaction temperature was reduced and made the catalyst more suitable for air conditioning systems in respect to energy consumption. When the specific degradation rate was less than 1500 mg/(g.h), the catalytic reaction was dominated by the diffusion rate of formaldehyde molecules onto the catalyst surface, and both the air-flow rate and initial formaldehyde concentration caused proportional change of the specific degradation rate. The maximum catalytic capacity could be as high as 1800 mg/(g.h), but was hard to achieve by changing reaction conditions.