Light pollution is an important issue that requires effective strategies to mitigate its negative effects while meeting the needs of the community. People’s perceptions of light pollution can influence their behaviour and attitudes towards lighting practices, thereby impacting the success of light pollution reduction effort and improvements in urban quality of life. However, people’s feelings about the lighted environment can be influenced by personal experiences, expectations, and cultural background, leading to different perceptions of lighting than what is actually present. To understand the perception of light pollution, a street survey was conducted in Hong Kong with 220 pedestrians across three site locations. The survey collected information on demographics and assessed perceptions of illuminance, colour temperature, uniformity, and glare, which formed the perceived lighting quality (PLQ) index. The results showed that there is no difference in the level of comfort between males and females or between younger and older participants under certain lighting conditions. However, individuals with lower education levels reported significantly lower comfort levels compared to those with higher education levels. The study also found a strong negative correlation between PLQ and perceived illuminance level. Additionally, both perceived colour temperature and glare level have a significant correlation with PLQ. Perceived illuminance has a weak correlation with perceived colour temperature and glare level, but perceived illuminance increases with perceived glare. Policymakers and lighting designers need to consider the perceptions of light pollution to develop effective strategies that meet the needs of the community.

Excessive artificial light disrupts our lives and poses health risks. In mixed-use urban areas, commercial lighting conflicts with residential activities. Vertical towers exacerbate the issue, as lower-level lighting affects higher-level occupants, and more research is needed to understand the vertical dispersion of light and its impact on sleep disturbance. This work offers a simple mathematical model for height dependence of illuminance in an urban building. It correlates basic measurements to reduce the values of the Exponent (n) and Linear (Coeff2) coefficients in a standard power-law curve. The collection of only a few data points can help to investigate the extent of the lighting spread at various floors of the building. Even with the complex lighting environment in Hong Kong, the methodology is exercised in 8 sample buildings from 4 different neighbourhoods to show the insights from the testing results. The heights of the studied buildings range from 3 to 18 stories, and they are for residential and mixed use. While the average measured illuminance at the street level was between 37 lx and 303 lx for the 4 neighbourhoods, the average illuminance across building heights was 14 lx to 247 lx. The existence of multiple light sources on building facades disrupts the simple inverse-square relationship with a single light source. The power n values range from approximately -1.7 to -0.8, while the Coeff2 values range from 61 to 7603 for the measured buildings. These variations indicate deviations from the assumption of a single source and suggest higher luminance and the presence of light sources at higher heights. With the simple inverse-square relationship, the proposed methodology can help to determine the height where the recommended limit can be met given the light situation at the street level.

Excessive temperatures can result in the collapse of structural components, cracking, scaling, and condensation in heritage building structures. Numerous unregenerated residential heritage buildings use portable heaters to adjust the indoor temperature for the comfort of occupants. However, research on the impact of heaters on the preservation of heritage buildings is limited. This paper proposes a novel and systematic approach based on digital twin technology to improve thermal performance effectively in unregenerated heritage buildings by arranging the locations and settings of heaters for improving building preservation. This research extended the functionality of heritage building information modeling (HBIM) to support simulations and decision-making to improve the thermal performance for heritage building preservation. An approach was proposed to address the lack of information by integrating documents, information, and graphics into an HBIM model for heritage building preservation. The digital model process based on HBIM presented in this study can be an effective 3D model for computational fluid dynamics (CFD) simulations. To investigate the impact of the heater on heritage building deformation, a novel method was developed to couple CFD and structural simulation to analyze the thermal performance and building deformation of heritage buildings. The heritage building deformation resulting from the heaters' power setting and location was identified and quantified. In addition, using the proposed digital twin platform, heaters were controlled automatically. The thermal performance, building cracking and deformation were monitored and recorded automatically along the lifecycle. The improved heater location reduced the maximum total deformation of the heritage building body by at least 62.9 %.

Light pollution in recent years has drawn surging public concerns in Hong Kong. The improper management of the light sources causes pollution, particularly light trespass on the community level, which obstructs the residents. Yet more studies are expected to quantitatively and systematically assess the severity of the artificial light trespass problem, and to offer practical solutions for mitigation and urban management. This study was conducted on a typical high-density, mixed-use neighbourhood in Tsim Sha Tsui district. The study consists of on-site measurement and model simulation. Three illuminance measurements were conducted to evaluate the impact of light pollution on the streets and light trespass on the nearby buildings. It was found that the impacts on the buildings (mean illuminance of 3 lx) are less significant than on the streets (mean illuminance of 188 lx) for the target study area. Indoor measurement at various height levels showed a mean illuminance level of 0.6 lx, which is much lower than the international limit of 25 lx. Meanwhile, the modelling work, consisting of correlation, verification and regression analysis, was carried to bridge luminous flux from light sources and illuminance received at the target. A three-dimensional (3D) model was developed to mimic the actual situation and was used to identify the primary light sources causing impacts. While a growing number of research is found on measuring and modelling the intricate light pollution in such a micro scale that elevates explicitly the importance of extrapolating the light pollution effect vertically from street level to building level, direct simulation is still lacking. This study also refined and summarised the research methodology to serve as a feasible and organised protocol for setting up the measurement and modelling work. This can be adapted in future assessments on light trespass issues under similar circumstances elsewhere, like scientific research, urban planning, or property development projects.

The use of artificial light at night (ALAN) enables social and commercial activities for urban living. However, the excessive usage of lighting causes nuisance and waste of energy. Light is provided to illuminate target areas on the street level where activities take place, yet light can also cause trespass to residents at the floors above. While regulations are beginning to cover light design, simulation tools for the outdoor environment have also become more popular for assessing the design condition. Simulation tools allow visualisation of the impact of the selected light sources on those who are affected. However, this cause-and-effect relationship is not easy to determine in the complex urban environment. The current work offers a simple methodology that takes site survey results and correlates them with the simulation model to determine lighting impact on the investigated area in 3D. Four buildings in two mixed commercial and residential streets in Hong Kong were studied. Data collection from each residential building requires lengthy work and permission from each household. Therefore, a valid lighting simulation model could help determine the light pollution impact in the area. A light model using DIALux is developed and calibrated by correlating the simulated data with the actual measured data. The correlation value R2 achieved ranged from 0.95 to 0.99, verifying the accuracy of this model and matched from 340 lx to 46 lx for the lower to higher floors of one building and 10 lx to 4 lx for floors of another building. This model can also be applied to human health research, by providing light-level data on residential windows in an area or determining the environmental impact of a development project.

The article demonstrates that the Ger Plug-In, a housing prototype that combines the traditional Mongolian nomadic dwelling, or ger, with new construction, is a viable sustainable and affordable housing product that addresses urgent issues that have arisen from the growth of Ulaanbaatar’s ger districts. These settlements have no water supply, sewers or centralised heating, and households use coal and coke briquettes to heat their homes. The prototype provides the ger with electrical heating,, sanitation systems and improved thermal insulation. The pilot project was constructed in 2017 and on-site field measurements together with numerical simulation have been used to calculate its Energy Use Intensity (EUI). By using both quantitative and qualitative methods, the results show that the Ger Plug-In meets the EUI criteria to be eligible for green mortgages provided by the Green Climate Fund. Household surveys were conducted to ascertain the financial capacity of residents. By proving its qualification for low interest rate mortgages and by evidencing its market demand, the objective is to demonstrate that the product can have scalable impact for the 840,000 residents living in the ger districts.

With rapid urbanization, the use of external lighting to illuminate cities for night-time activity is on the rise worldwide. Many studies have suggested the excessive use of external lighting causes light pollution, which harms human health and leads to energy wastage. Although more awareness has been raised, there are not many regulations and guidelines available. As one of the cities most affected by light pollution in the world, Hong Kong has started exploring this issue within the general and business communities. However, studies that quantitatively evaluate the problem of light pollution in this city are lacking. This study aimed to assess light pollution quantitatively through measurement and numerical modelling. To achieve this, measurement protocols were developed, and site measurements were carried out in one of the known problem areas, Sai Yeung Choi Street in Mong Kok district. Through this exercise, both vertical and horizontal illuminances on the street level and the light distribution along the street were determined. An average level of 250 lx for the vertical illuminance was found, which was 3-4 times higher than the recommended brightness for normal activity. The light environment of the measured area was also modelled with the simulation program DIALux. This effort complemented the measurements by providing a means to increase the resolution on the light variation and to visualize light pollution in a 3D environment. The simulation results were verified by correlating the numerical model with measurements. The correlated model was exercised in a subsequent sensitivity study to predict possible outcomes with changing lighting pattern and lighting lumen level. This study serves to quantify this issue, which helps with the further development of effective solutions.

Underground heritage sites generally experience significant humidity, which results in the destruction of the surfaces and structures. This study establishes an underground heritage site preservation mechanism through a dynamic ventilation system based on digital twin technology. The aim is to control the relative humidity (RH) gradually on the air region near the walls of sites within the standard range and reduce adverse physical equipment effects and energy consumption of the system. Underground heritage site projects have more complex shapes with irregular and nonlinear arcs and height difference distributions. It is challenging to regenerate them. To achieve this objective, a model simplification rule for irregular heritage building information modeling (HBIM) technology was first established via computational fluid dynamics (CFD) simulation. Second, a meth-odology was developed to design a reliable and effective ventilation equipment and its layout based on CFD for irregular heritage sites. Compared with the scheme based on the optimal geometric rule arrangement, the number of pipes can be reduced by up to 25%. Third, a web-based digital twin platform combined with Internet of Things (IoTs) technology was established for achieving real-time control of the overall RH level of under-ground heritage sites within the standard range. The results present new solutions to control the RH of under-ground heritage sites for preservation. The proposed methodology can be used in typical underground heritage sites and illustrated by a real case. The validation encompassed development of digital environment for the real case and development of the ventilation system for its RH optimization.

Thermal comfort and indoor air quality (IAQ) are important to occupants’ wellbeing. Sensors are deployed for pollutant exposure assessments and long-term IAQ monitoring. How to optimize sensor placements in single rooms has been studied. However, limited studies on sensor placement in a multi-zone indoor environment have been conducted. On a typical office floor, room partitions can be changed by tenants, and conducting field measurements in the occupied tenant areas is not allowed. It is difficult to determine where to install a sensor. The related studies rarely consider different weather conditions and ventilation system settings when performing optimization. This study aims to develop a methodology to optimize temperature and CO2 sensor placement for thermal comfort and IAQ monitoring in a multi-zone environment under limited field measurement. Supported by building information modeling (BIM) technology, different seasons, MVAC system settings, and occupancy scenarios were taken into account when optimizing sensor placement. How to overcome limited information of the inaccessible regions by applying the conservation equations as well as considering the MVAC layout of the floor and sources of heat and CO2 emission were also illustrated. The methodology was illustrated using a validated Computational fluid dynamics (CFD) model of a typical office floor. With the use of genetic algorithm (GA) and machine learning, the generated sensor placements fulfilled coverage requirements from LEED and over 70% of the regions with significant fluctuation in temperature and CO2 are inside the sensing range of sensors. The developed approach can be applied in both new and existing buildings.

When studying Indoor Air Quality (IAQ) in commercial buildings by conducting Computational fluid dynamics (CFD) simulations, the solution domain usually includes studied rooms or floor volumes only. The air shafts connected to the studied room and floor were rarely considered. Previous studies, which focused on analysis and simulation of air movement inside ventilation and exhaust shafts, seldom considered how the corresponding air movement affects the connected floors. Field measurement cannot be conducted in inaccessible tenant areas to support CFD simulations. The current practice to calculate solar heat load and distribution for CFD simulation with surrounding buildings included is computationally expensive. The objective of this study is to develop a methodology to investigate how velocity variations along the fresh air shafts affect thermal comfort and IAQ of multiple floors under limited obtainable field measurements. Steadystate CFD simulations were conducted on fresh air shafts and office floors of a typical commercial building. Building Information Modeling (BIM) technology was applied to create models to represent the geometry of fresh air shafts and office floors accurately. In addition, BIM technology not only supports CFD simulations but also provides geometric, semantic and location information for solar analysis. The CFD results were validated using measured results. The impact of shaft design changes on the ventilation performance of the shaft and the indoor air quality on the floors was investigated using validated models. In the case of dividing the shafts into two parts, the overall fresh air distribution, thermal comfort and indoor air quality were improved.

Computational fluid dynamics (CFD) is a powerful tool for performing indoor airflow analysis. The simulation results are usually validated with measurement results for accuracy in reflecting reality. When conducting CFD for simulating air flow in a multiple-zone indoor environment with different boundary conditions in different regions, the validation of the CFD model becomes sophisticated. To improve the accuracy of the simulation, boundary conditions need to be adjusted based on how significant the influence factors are affecting the multi-zone CFD model, which few studies have been conducted on. The objective of this study is to investigate the impact of influence factors on temperature and carbon dioxide concentration distribution of a validated CFD model of a typical office floor using ANSYS Fluent. This study provides insights on how to fine-tune a complex model to reflect the actual air flow and how the air quality and human comfort in different zones on the same floor could be affected by influence factors. The influence factors investigated are: (1) size of door gaps, (2) solar radiation and (3) number and orientation of occupants. The velocity variations caused by different door gap sizes were studied for improving multi-zone simulation accuracy by adjusting door gap sizes. To study the significant impact of solar heat on multi-zone environment, the sensitivity of different regions of the office floor to solar heat amount and distribution was analyzed by conducting solar analysis under different weather conditions. Impact of occupants on temperature and carbon dioxide concentration distributions in multi-zone environment were investigated by considering different numbers and facing directions of occupants in different regions of the office floor. In addition, this study demonstrates how to modify the influence factors efficiently using building information modeling (BIM).

Mongolia is experiencing unprecedented urbanization along with recent economic growth. Ulaanbaatar is known to be the coldest capital in the world and heating demand is very high during the long winter season. Due to the increase of coal burning to provide heat, there is an urgent need to improve housing and to reduce energy use and air pollution. Currently, there is a revitalization of the Ger area of Mongolia and this presents a good opportunity to redevelop the region into an ecologically designed district with sustainable housing. Such a redesign will result in energy saving and air pollution reduction. With this goal in mind, a pilot project called Create Accord Living Environment (CALE), was developed to demonstrate living conditions with a new house design that is cost effective for Mongolia. This paper presents the house performance using an energy simulation and the results are correlated with measurement data taken during the wintertime. The average energy use intensity (EUI) for 5 CALE houses was found to be 112 kWh/m2/yr. This is a 71% energy savings compared to a typical detached house with a modern and efficient house design. If it is possible to redevelop 1000 houses in the Ger area, an estimated 6.5 kton/yr in carbon emission can be saved. In addition, a parametric study was conducted to investigate the impact of different construction materials, craftsmanship quality, and occupants' behavior on the house's energy efficiency. The proposed housing structures, which provide a comfortable living space with significantly reduced energy utilization, serves as a potential model for development both within Mongolia as well as for other similar climates.

Studies of the indoor airborne microbiome have mostly been confined to a single location and time point. Here, we characterized, over the course of a year, the geographic variation, building-function dependence, and dispersal characteristics of indoor and outdoor airborne microbiomes (bacterial members only) of eight mechanically ventilated commercial buildings. Based on the Sloan neutral model, airborne microbiomes were randomly dispersed in the respective indoor and outdoor environments and between the two environments during each season. The dominant taxa in the indoor and outdoor environments showed minor variations at each location among seasons. The airborne microbiomes displayed weak seasonality for both indoor and outdoor environments, while a weak geographic variation was found only for the indoor environments. Source tracking results show that outdoor air and occupant skin were major contributors to the indoor airborne microbiomes, but the extent of the contribution from each source varied within and among buildings over the seasons, which suggests variations in local building use. Based on 32 cases of indoor airborne microbiome data, we determined that the indoor/outdoor (I/O) ratio of PM2.5 was not a robust indicator of the sources found indoors. Alternatively, the indoor concentration of carbon dioxide was more closely correlated with the major sources of the indoor airborne microbiome in mechanically ventilated environments.

Metabolically active bacteria within built environments are poorly understood. This study aims to investigate the active airborne bacterial microbiota and compare the total and active microbiota in eight mechanically ventilated buildings over four consecutive seasons using the 16S rRNA gene (rDNA) and the 16S rRNA (rRNA), respectively. The relative abundances of the taxa of presumptive occupants and environmental origins were significantly different between the active and total microbiota. The Sloan neutral model suggested that ecological drift and random dispersal played a smaller role in the assembly of the active microbiota than the total microbiota. The seasonal nature of the active microbiota was consistent with that of the total microbiota in both indoor and outdoor environments, while only the indoor environment was significantly affected by geography. The relative abundances of the active and total taxa were positively correlated, suggesting that the high-abundance members were also the greatest contributors to the community-level metabolic activity. Based on the rRNA/rDNA ratio, the low-abundance members consistently had a higher taxon-level metabolic activity than the high-abundance members over seasons, suggesting that the low-abundance members may have the ability to survive and thrive in the indoor environment and their impact on the health of occupants cannot be overlooked.

It is important to monitor the indoor air quality and thermal comfort of an office environment for the wellbeing of its occupants, and, to do so, computational fluid dynamics simulation is more cost-effective than measuring an entire floor. Computational fluid dynamics simulation has been used by previous studies for single rooms and partitioned spaces, but not for office floors with multi-zone ventilation systems, and air infiltrations between different zones through closed doors have been neglected. Also, since it is often not possible to take measurements across an entire floor due to concerns of tenant privacy, few studies have used the limited obtainable field measurements to validate multi-zone computational fluid dynamics simulations. This study describes a methodology to conduct indoor multi-zone steady-state computational fluid dynamics simulation, with improved accuracy, on a typical office floor where there is limited information on carbon dioxide concentrations and temperatures. Heat and mass conservation equations were used to compensate for the lack of information. The mechanical ventilation and air conditioning layout was considered along with the sources of heat and carbon dioxide emissions. To improve the accuracy of the simulation on temperature, a solar analysis, based on building geometry, orientation, materials, location, and weather, was conducted to estimate any solar heat gain and distribution through curtain walls. Building information modeling supported the solar analysis and provided geometric information for the computational fluid dynamics simulation. The methodology was validated by a real case of a commercial building, where the accuracy of the temperature simulation improved by 9.9%.

Currently, there is little information pertaining to the airborne bacterial communities of green buildings. In this case study, the air bacterial community of a zero carbon building (ZCB) in Hong Kong was characterized by targeting the bacterial 16S rRNA gene. Bacteria associated with the outdoor environment dominated the indoor airborne bacterial assemblage, with a modest contribution from bacteria associated with human skin. Differences in overall community diversity, membership, and composition associated with short (day-to-day) and long-term temporal properties were detected, which may have been driven by specific environmental genera and taxa. Furthermore, time-decay relationships in community membership (based on unweighted UniFrac distances) and composition (based on weighted UniFrac distances) differed depending on the season and sampling location. A Bayesian source-tracking approach further supported the importance of adjacent outdoor air bacterial assemblage in sourcing the ZCB indoor bioaerosol. Despite the unique building attributes, the ZCB microbial assemblage detected and its temporal characteristics were not dissimilar to that of conventional built environments investigated previously. Future controlled experiments and microbial assemblage investigations of other ZCBs will undoubtedly uncover additional knowledge related to how airborne bacteria in green buildings may be influenced by their distinctive architectural attributes.

During winter-time in Mongolia, the air pollution is so severe that it threatens the citizens' health. Ulaanbaatar is the capital city of Mongolia, and its population represents about half of the total population of Mongolia. The majority of people in the Ger area, approximately 50% of population of Ulaanbaatar, rely on direct coal burning to generate the required heat to maintain a comfortable environment in the cold season. The heavy reliance on coal leads to catastrophic air pollutant emissions including carbon dioxide, sulphur dioxide, nitrogen oxides and particulate matter, which leads to global warming, climate change and human health. As it is identified that building insulation retrofit is one of the best ways to reduce the reliance on coal consumption due to the improved heat retention and air tightness, a tool, named "FIXIT" has been developed to quickly quantify the impact from insulation retrofit. This paper presents how "FIXIT" was developed and is applied to help house owners to understand their building performance. Not only can "FIXIT" be applied for individual houses, it can also be used to estimate the reduction of air pollution from coal burning due to insulation retrofit. With "FIXIT", it is estimated that about 530 ktons of carbon emissions reduction can be targeted by applying building insulation retrofit, if around the 100,000 detached houses in Ulaanbaatar apply insulation retrofit. By highlighting the advantages on the building performance, "FIXIT" can encourage more house owners to improve their house insulation quality and thus contribute to the air quality, creating a cleaner and healthier environment and saving on fuel use. (C) 2018 Published by Elsevier B.V.

Vertical City Air Purification System was designed to reduce the aerosol counts at the playground next to a major traffic road. Columns with air grilles are arranged in circle to create a close loop system. Computational simulation is adopted to study three scenarios. The first simulation covers conventional wind block technology, where strong wind speed is created between columns to stop pollutants from entering the premise. However, it is observed that polluted air can enter the development from the head above. Hence, two other options are created, one with supply air directing to the centre of the development, the other with underfloor air supply. It is studied that at outlet velocity of 6.5 m/s, the underfloor system can contribute to around 40% pollution reduction using MERV13 filter, which is more than 24% better than the baseline. Traditionally, outdoor pollution mitigation deems to be contributing insignificantly. The positive simulation result marks a potential for future outdoor pollution mitigation development.

Worsening air pollution poses a large and growing public health problem. More than 80% of people currently live in urban areas with air quality levels that exceed WHO particulate matter (PM) concentration limits. They are subjected to a higher risk of cardiac arrests, peripheral vascular disease (PVD), lung cancer, respiratory diseases, and asthma. Poor air quality is mainly caused by rapid urbanisation and industrialisation, which require high energy consumption and transportation flow. Air pollutants are emitted from power plants and vehicles, and are trapped in the built environment, to which people on the street are exposed all the time. In view of the pressing need to combat roadside air pollution, Arup and Sino Green have developed a novel, patented system called the City Air Purification System (CAPS) that won the second prize of the Construction Industry Council (CIC) Innovation Award 2015. The prototype, a stand-alone system with a ventilation system that filters out pollutants and purifies air for pedestrians in proximity to the system, has been tested in Hong Kong and Beijing and has effectively reduced air pollutant (PM2.5 and PM10) concentration within the system by 30% to 70% under various ambient conditions. This paper focuses on the simulations and analysis showing the improvement of roadside air quality resulting from CAPS when it is incorporated into buildings located in a busy district in Hong Kong.