High Occupant Density Research Articles

Seasonal concentrations and size distributions of culturable bacterial aerosols inside and outside university classrooms – A case study in Beijing

The risks of cross-infection among occupants will be greatly increased by the high occupant densities and mobility inside and outside university classrooms. In order to know the distribution characteristics of culturable bacterial aerosols in such public environments, during normal didactic activities, indoor and outdoor bacterial aerosols were sampled from December 2018 to December 2019 by using Andersen six-stage impactor in 11 university classrooms. The yearly average concentration of outdoor bacterial aerosols was 314 ± 229 CFU/m3, and the size mainly distributed within 2.1–4.7 μm. For unoccupied condition, indoor culturable bacterial aerosols were dominated by outdoors (R2 = 0.78), the yearly average concentration was 254 ± 130 CFU/m3, and the size mainly distributed within 1.1–3.3 μm. For occupied condition, the yearly average concentration of indoor bacterial aerosols was 494 ± 263 CFU/m3, and the size mainly distributed in the range of 1.1–4.7 μm. With human presence, occupants instead of outdoor air becoming the primary source of indoor culturable bacterial aerosols. The seasonal emission rates of bacterial aerosols resulted from occupants were in the order of summer > autumn > spring > winter, corresponding to 1538 ± 646, 850 ± 292, 592 ± 254, and 388 ± 219 CFU/person/h. Air temperature, relative humidity, and PM10 mass concentrations were main environmental factors (p < 0.01) to positively influence the concentrations distribution of indoor culturable bacterial aerosols. The results can provide basic data for evaluating the risks of occupants expose to bacterial aerosols and improving indoor microbial air quality in university classrooms.

Environmental quality in primary schools and related health effects in children. An overview of assessments conducted in the Northern Portugal

Since children are far more vulnerable than adults to the effects of air pollution and spend about a third of their day in school, strict control of indoor environments in educational buildings is paramount to properly identify, manage and mitigate putative environmental risks for children. In this context, this work aimed to provide a holistic view on the outcomes obtained from the national ARIA project, which was focused on broadening the knowledge on the effects on children’s health of the exposure to schools’ indoor air. In particular, this work performed a comprehensive investigation of the indoor air quality (IAQ) in 20 public primary schools located in Porto (Northern Region, Portugal). This paper presents the results of the investigation along with the recently published main outcomes of ARIA on (1) the characteristics of the environment surrounding the surveyed buildings, and (2) the school’s environment-related health effects in school-age children from the studied classrooms. The investigation consisted in an extensive assessment plan conducted in 71 classrooms to assess temperature, relative humidity, carbon monoxide and dioxide, particulate matter (PM2.5, PM10, and ultrafine particles), nitrogen dioxide, ozone, volatile organic compounds, formaldehyde, acetaldehyde, airborne fungi, bacteria and endotoxins, and investigate their respective sources, during the cold seasons of 2014–2015. A series of studies was also launched to investigate school environment-related health detriments in 916 children. The results showed that comfort and ventilation issues and/or indoor pollutant levels that exceeded recommended limits were found in a substantial number of the classrooms surveyed. The high density of occupants, deficient ventilation, soil characteristics, presence of indoor pollution sources (e.g. classroom materials and consumer products) and outdoor pollution were some of the factors that seemed to explain the high air stuffiness and/or indoor pollution load identified in classrooms. In fact, some of indoor pollutants detected, even at low exposure levels, were associated with the development of respiratory symptoms in school-age children. Moreover, results from this work have also shown that the characteristics of the environment surrounding the schools, namely the presence of green spaces and species richness, can be major determinants of respiratory health among school-age children. Overall, the body of evidence generated from the ARIA project can support new evidence-based perspectives for promotion of health in educational buildings.

Influencing factors of carbonyl compounds and other VOCs in commercial airliner cabins: On-board investigation of 56 flights.

Volatile organic compounds (VOCs) as a non-negligible aircraft cabin air quality (CAQ) factor influence the health and comfort of passengers and crew members. On-board measurements of carbonyls (short-chain (C1 -C6 )) and other volatile organic compounds (VOCs, long-chain (C6 -C16 )) with a total of 350samples were conducted in 56 commercial airliner cabins covering 8 aircraft models in this study. The mean concentration for each individual carbonyl compound was between 0.3 and 8.3μg/m3 (except for acrolein & acetone, average=20.7μg/m3 ) similar to the mean concentrations of other highly detected VOCs (long-chain (C6 -C16 ), 97% of which ranged in 0-10μg/m3 ) in aircraft cabins. Formaldehyde concentrations in flights were significantly lower than in residential buildings, where construction materials are known formaldehyde sources. Acetone is a VOC emitted by humans, and its concentration in flights was similar to that in other high-occupant density transportation vehicles. The variation of VOC concentrations in different flight phases of long-haul flights was the same as that of CO2 concentration except for the meal phase, which indicates the importance of cabin ventilation in diluting the gaseous contaminants, while the sustained and slow growth of the VOC concentrations during the cruising phase in short-haul flights indicated that the ventilation could not adequately dilute the emission of VOCs. For the different categories of VOCs, the mean concentration during the cruising phase of benzene series, aldehydes, alkanes, other VOCs (detection rate>50%), and carbonyls in long-haul flights was 44.2µg/m3 , 17.9µg/m3 , 18.6µg/m3 , 31.5µg/m3 , and 20.4µg/m3 lower than those in short-haul flights, respectively. Carbonyls and d-limonene showed a significant correlation with meal service (p<0.05). Unlike the newly decorated rooms or new vehicles, the inner materials were not the major emission sources in aircraft cabins. Practical Implications. The on-board measurements of 56flights enrich the VOC database of cabin environment, especially for carbonyls. The literature review of carbonyls in the past 20years contributes to the understanding the current status of cabin air quality (CAQ). The analysis of VOC concentration variation for different flight phases, flight duration, and aircraft age lays a foundation for exploring effective control methods, including ventilation and purification for cabin VOC pollution. The enriched VOC data is helpful to explore the key VOCs of aircraft cabin environment and to evaluate the acute/chronic health exposure risk of pollutants for passengers and crew members.

Characterization of the public transit air microbiome and resistome reveals geographical specificity

BackgroundThe public transit is a built environment with high occupant density across the globe, and identifying factors shaping public transit air microbiomes will help design strategies to minimize the transmission of pathogens. However, the majority of microbiome works dedicated to the public transit air are limited to amplicon sequencing, and our knowledge regarding the functional potentials and the repertoire of resistance genes (i.e. resistome) is limited. Furthermore, current air microbiome investigations on public transit systems are focused on single cities, and a multi-city assessment of the public transit air microbiome will allow a greater understanding of whether and how broad environmental, building, and anthropogenic factors shape the public transit air microbiome in an international scale. Therefore, in this study, the public transit air microbiomes and resistomes of six cities across three continents (Denver, Hong Kong, London, New York City, Oslo, Stockholm) were characterized.ResultsCity was the sole factor associated with public transit air microbiome differences, with diverse taxa identified as drivers for geography-associated functional potentials, concomitant with geographical differences in species- and strain-level inferred growth profiles. Related bacterial strains differed among cities in genes encoding resistance, transposase, and other functions. Sourcetracking estimated that human skin, soil, and wastewater were major presumptive resistome sources of public transit air, and adjacent public transit surfaces may also be considered presumptive sources. Large proportions of detected resistance genes were co-located with mobile genetic elements including plasmids. Biosynthetic gene clusters and city-unique coding sequences were found in the metagenome-assembled genomes.ConclusionsOverall, geographical specificity transcends multiple aspects of the public transit air microbiome, and future efforts on a global scale are warranted to increase our understanding of factors shaping the microbiome of this unique built environment.

Educational building retrofit under climate change and urban heat island effect

Climate change (CC) and urban heat island (UHI) are important environmental forces that have serious consequences for the existing buildings, such as increased resource consumption and environmental footprint, adverse human health effects and reduced occupant comfort. In this context, educational buildings represent a critical category amongst other building typologies, due to their high energy use, high occupant density, atypical daily/annual occupancy patterns, and their occupants’ high vulnerability to heat. Poor indoor conditions can reduce the health and productivity of students and teachers, worsen learning performance and reduce attendance. Retrofitting educational buildings is an effective solution to tackle this challenge. This study investigates the impact of CC&UHI on educational building performance and demonstrates the effectiveness of passive retrofit scenarios targeting CC&UHI mitigation and adaptation. These investigations are based on a systematic approach that consists of (i) the generation and analyses of CC&UHI-modified weather datasets, and (ii) simulation-based comparative analyses of the as-is building and various retrofit scenarios. An existing secondary school building in Ankara, Turkey is selected as a case study for evaluations of the selected performance indicators including energy use, global warming potential (GWP) and thermal comfort. Obtained results indicate that total energy consumption can be reduced up to 50% with retrofit, whereas possible reductions in indoor discomfort are even more pronounced, underlining the significance of selecting the optimal combination of passive measures for maximum impact towards the adaptation of the existing educational buildings to the changes in climatic conditions.

Efficiency evaluation of a floor standing air conditioner with different installation positions and air supply parameters applied to a large laboratory

In recent years, floor standing air conditioners (FSACs) have been widely used in large educational buildings in China because of their high refrigerating power and ease of installation. The operation performance and energy consumption of FSACs has attracted increasing attention: because the installed position of an FSAC influences its performance, to obtain information about the laboratory's cooling loads and the boundary conditions for numerical simulation research during experimental periods and non-experimental periods, first, in situ measurements were conducted in a typical large laboratory with high occupant density. Second, computational fluid dynamics models of three FSACs in their installed positions were established to enable the quantitative study of the influences of the FSAC's position on ventilation, air conditioning, and disease transmission in the laboratory when the door was open. The simulation results showed that, when the FSAC was installed diagonally opposite the door, the optimum cooling performance and volatile organic compound removal occurred when the door was open. Finally, this study involved a data envelopment analysis model to evaluate the efficiency of 27 cases. Overall, optimal performance was achieved when the FSAC was installed diagonally opposite the door with an air supply temperature of 19 °C and a velocity of 4.5 m/s. This research could also be applied to help with the positioning and set-up of FSACs in other similar large spaces.

IDENTIFYING UNHEALTHY HOUSES IN KERINCI DISTRICT, INDONESIA

Background: Healthy houses in developing countries are a critical factor in human health, as the increase in population is not balanced by improvements in local community welfare. This has negative impacts on the environment and human health. Purpose: The aim of this study was to identify unhealthy houses in Kerinci, Indonesia. Method: This research used a descriptive cross-sectional approach. A survey of 122 houses was conducted to determine the characteristics of houses in Kerinci District, Jambi Province, Indonesia. Stratified random sampling was used to obtain representative healthy house data, by using four repetitions on each single question to minimize errors. Results: The results showed that 90% of respondents had a high occupant density. A high number of diseases were already experienced by residents in the area. These diseases were an indication that the area could be classified as unhealthy and included diarrhea (20%), acute respiratory infections (ARI; 13%), malaria (10%), skin diseases (15%), and other diseases (29%). Only 12% of the total respondents reported having no diseases. Conclusion: In the Kerinci District, 98% of houses were classified as unhealthy and as having potentially negative impacts on the health of residents. We recommend the government establish regulations to improve the health of houses and increase economic growth in Kerinci District, Indonesia.

Study of Risk Assessment of Indoor NH3 in Two Urban Households of NCR-Delhi

Indoor air pollution is a matter of serious concern in the mega cities which are grappling with poor air quality. There are very few reports available that discuss the indoor air quality of gaseous ammonia (NH3). This study reports the abundance and risk assessment of NH3 in two distinct urban households of Delhi city during July 2017 to June 2018. Results showed that the NH3 concentrations were consistently higher during entire sampling period at the Dwarka household (DH) site which represented the residential sector having an average value of 102.5 µg/m3, as compared to the Mayapuri household (MH) site which represented the industrial sector having an average value of 57.2 µg/m3. The spatio-temporal analysis suggested a characteristic seasonal influence as indoor concentrations were very high during monsoon season following the order, monsoon &gt; summer &gt; post-monsoon ≥ winter, at DH site but indoor NH3 at MH site did not show any remarkable seasonal variation except a sweeping increase during monsoons. Short term and long term health risk characterisation using multiple appropriate toxicological end limits for NH3 in the two households showed that at its present concentrations indoor NH3 cannot be a health hazard to the inmates. However, it does not fail to escape our notice that mushrooming urban areas with their complex problems such as poor sanitation, industrialisation, waste management, high vehicular traffic, high occupant density, etc. have become major hubs of continual rise in indoor ammonia.

Evaluation of the Dispersion Stability of AZO Mesocrystals for Their Processing into Functional Thin Films Using Small Angle X-ray Scattering

Within the scope of the comprehensive elucidation of the entire process chain for the production of highly functional thin films made of semiconducting aluminum-doped zinc oxide ( A Z O ) nanocrystals, this work deals with the detailed investigation of the stabilization sub-process, considering the requirements for the subsequent coating process. An innovative investigation procedure using non-invasive small angle X-ray scattering ( S A X S ) is developed, enabling an evaluation of qualitative and quantitative dispersion stability criteria of sterically stabilized A Z O nanocrystals. On the one hand, qualitative criteria for minimizing layer inhomogeneities due to sedimentation as well as aggregate formation are discussed, enabling a high particle occupancy density. On the other hand, a procedure for determining the A Z O concentration using S A X S , both in the stable phase and in the non-stabilized phase, is demonstrated to provide a quantitative evaluation of the stabilization success, having a significant impact on the final layer thickness. The obtained insights offer a versatile tool for the precise stabilization process control based on synthesis process using S A X S to meet coating specific requirements and thus a successful integration into the entire process chain for the production of functional A Z O thin films.

Air distribution of oxygen supply through guardrail slot diffusers in high-altitude hypoxic areas

Oxygen supply is necessary for high-altitude hypoxic areas, especially public spaces with high occupant densities. Traditional oxygen supply systems, including individual oxygen supplies (IOS), distributed centralized oxygen supplies (DCOS) and diffusion-type oxygen supplies (DTOS), are limited in completing oxygen delivery tasks by the balance between low cost and high efficiency. This study elaborated a method for air distribution by adopting guardrail slot diffusers (GSDs) for oxygen-rich air delivery directly to the human breathing zone without changing the basic layouts of high and large spaces. The dynamic breathing zone was obtained by monitoring the swing of people waiting beside a guardrail. Two indicators, the target value of oxygen concentration and the oxygen supply efficiency, were introduced to facilitate the evaluation of oxygen supply through GSDs. Compared with oxygen supply through other existing air distribution systems in high and large spaces, the optimized GSDs have a 9%–27% higher effectiveness, as expressed in terms of the target value of oxygen concentration. The oxygen supply efficiency is 271%–658% higher. The implementation of the system was studied at altitudes of 2000 m, 3000 m, 4000 m and 5000 m, which proved that this oxygen supply system has better implementation effects. By increasing the height of the guardrail by 100 mm, the GSDs can meet the oxygen demand for air inhaled by European and North American adults. The results indicate that this method realized efficient oxygen supply in high-altitude hypoxic areas while reducing oxygen consumption and investment costs.

Impact of different ventilation strategies on aircraft cabin air quality and passengers’ comfort and well-being – the ComAir study

Indoor air quality can affect occupants in numerous ways. Especially carbon dioxide (CO2) and volatile organic compounds (VOCs) have been debated in their effects on health, well-being, and cognition of people. Aircraft cabins present indoor environments with distinctive features, where passengers are exposed to a mixture of outside and recirculated air. They include conditions such as high occupant density, inability to leave the environment, low relative humidity and need for pressurization. The ComAir study, funded by the Clean Sky 2 Initiative of the European Union, aims to investigate the impact of reducing outdoor air intake in the total volume of air supplied on cabin air quality and passengers’ wellbeing. The main experiment of the study uses a 2(‘occupancy’) X 4 (‘air ventilation regime’) factorial design with stratified randomization of participants. Occupancy denotes the number of people in the aircraft (half vs. full) and varies the psychological important wellbeing factor of proxemics. The four air ventilation regime levels are: Baseline with typical aircraft airflows regimes per person, ASHRAE 161 requirement (standard recommendation), ASHRAE 161 half (half of the recommended flow), and a recirculation regime with a target CO2 concentration close to regulatory limit. This paper presents the background and experimental procedure of ComAir and gives some preliminary results on environmental conditions and subjects’ wellbeing and health under the baseline air ventilation regime.

A Study on Energy-Saving Technologies Optimization towards Nearly Zero Energy Educational Buildings in Four Major Climatic Regions of China

An educational building is a kind of public building with a high density of occupants and high energy consumption. Energy-saving technology utilization is an effective measure to achieve high-performance buildings. However, numerous studies are greatly limited to practical application due to their strong regional pertinence and technical simplicity. This paper aims to further optimize various commonly used technologies on the basis of the current national standards, and to individually establish four recommended technology selection systems corresponding to four major climatic regions for realizing nearly zero energy educational buildings (nZEEBs) in China. An educational building was selected as the case study. An evaluation index of energy-saving contribution rate (ECR) was proposed for measuring the energy efficiency of each technology. Thereafter, high energy efficiency technologies were selected and implemented together in the four basic cases representing different climatic regions. The results showed that the total energy-saving rate in severe cold regions increased by 70.74% compared with current national standards, and about 60% of the total energy-saving rate can be improved in cold regions. However, to realize nZEEBs in hot summer and cold winter regions as well as in hot summer and warm winter regions, photovoltaic (PV) technology needs to be further supplemented.

The Effect of High Occupancy Density on IAQ, Moisture Conditions and Energy Use in Apartments

Apartments built in Sweden during the record years 1961–1975 with the aim to remedy the housing shortage and abolish poor standards, were designed for a normal-sized family of 2–4 persons. The mechanical ventilation system, if existing, was primarily designed to ensure an air exchange in the apartment according to Swedish building regulations. During the last few years, the number of overcrowded apartments has increased due to housing shortage in general but also due to migration. Another aspect is that the ventilation in many apartments built during the record years is already insufficient at normal occupant load. The question is how doubling or tripling the number of occupants and thus, the moisture load will affect the risk of bad air quality and moisture damage. To find out, simulations were made to estimate whether it is possible to obtain sufficient air quality and low risk of moisture damage by only increasing the ventilation rates in existing systems or introducing new ventilation systems with and without heat recovery and what the consequence would be in terms of the additional energy demand. Measurements from earlier studies of CO2 and moisture supply in Swedish apartment buildings were used as input data.

Effect of mechanical ventilation on air infiltration rate in a concert hall

Due to high occupant density, fresh air is essential for audience in a concert hall. Generally, mechanical ventilation system is used to supply outdoor fresh air. Apart from that, uncontrolled air leakage across building exterior (i.e., air infiltration) is also a source of outdoor fresh air. Though ASHRAE requires a positive pressure (i.e., zero infiltration rate) for mechanically ventilated rooms, positive pressure is difficult to be maintained under poor building airtightness or low mechanical ventilation rates. When the positive pressure is not achieved, the existence of air infiltration brings about outdoor air pollutants infiltrating indoors and excessive fresh air cooling/heating load. Therefore, to maintain a good indoor environment and an appropriate fresh air rate, the effect of mechanical ventilation on air infiltration rate must be figured out. This study investigates the variation laws of infiltration rate with mechanical ventilation rate in a concert hall. Infiltration rates under different mechanical ventilation rates were measured based on the particle mass balance method. It is concluded that the relationship between the two rates conforms to the theoretical model proposed by the authors’ previous study.

Pesantren’s Dormitory Design Parameters Based on Student’s Preference and Adaptation

Currently the development of pesantren in Indonesia is very rapid, while there is still no concept that is used as a reference in designing of the dormitory building. There are several standards or references used in dormitories but currently only found for campus dormitories. In addition, there are some problems in pesantren dormitory such as infrastructure that is less supportive and very high occupancy density, therefore students make adaptations. This study aims to formulate the parameters used in designing pesantren based on preferences and adaptation. Preference is included because there is relationship between preference and adaptation. The method used is qualitative by comparing from some literatures. The results consist of thread of thought, determining of pesantren and variable, indicator used. There are five thread that used to formulated design concept, among others existing, typology, preference, adaptation and proposal design. Variable and indicators of activity, facility and environmental scope can be assessed on student preference and adaptation in any contexts and type of pesantren. Further, the upcoming result of parameter can be set as the underlying consideration for the designing of pesantren dormitory.

Research on evaluation and optimization of sustainable indoor environment of public buildings in Xi’an in summer

ABSTRACT There have been more concerns over energy resource depletion and indoor comfort improvement along with the increased time spend in a building. Building operation requires more energy in the spaces of high occupancy density in public buildings in summer because most energy has been consumed to make the indoor environment comfortable. Therefore, there is a conflicting issue for optimization, which is minimum energy consumption vs. maximum indoor comfort. In this paper, the indoor comfort model was established based on the weights of the thermal environment and air quality. The indoor air temperature, indoor relative humidity and indoor CO2 concentration as KPI (Key performance indicators) are optimized dynamically according to different outdoor meteorological parameters and different indoor occupancy density by an improved multi-objective optimization method of Non-dominated Sorting Genetic Algorithm II (NSGA-II). A single suitable solution from the non-inferior solutions is selected by the method of fuzzy comprehensive decision. The single solution of those KPI can be used as the set point of air-conditioning controller. A case study was carried out and the corresponding simulation of optimization of energy and comfort was presented. The results showed that the methodology can achieve the maintenance of indoor comfort and energy consumption reduction.

Indoor CO2: potential criticalities and solutions

Carbon dioxide (CO2) has been conventionally regarded as a global problem, due to the well-known effects of fossil fuel combustion to the climate of our planet. However, this paper aims at highlighting the role of CO2 from another perspective, i.e. by considering the effects of CO2 on the health and well-being of the occupants of indoor spaces. The exposure to CO2 air concentrations &gt; 1,000 ppm causes symptoms like headache, dizziness, sleepiness and loss of attention, which may negatively influence the learning capability and the productivity of students and workers. In this sense, schools and universities are particularly vulnerable, due to the high density of occupants in classrooms and to the importance of the role of education in training the future members of the society. In the light of this issue, the present paper will provide examples of the incorrect design of indoor environments and, meanwhile, will propose simple solutions to monitor the problem of indoor CO2 concentration and improve the indoor environmental quality of public places.

An Experimental Study of Ascent and Descent Movement of People on Long Stair with High Occupant Density

This paper presents an experimental study of the movements of both ascent and descent in a high occupant density 20-level building in order to exploit the characteristics of occupant movement on long stairwells. The movement processes of the participants are recorded in order to estimate both overall and local movement speeds, as well as flow rate and occupant density in the stairwell. When a merging flow is presented, the average movement time from one floor to the next is 35.8 s ± 15.6 s, and 37.3 s ± 10.6 s for ascent and descent movement, respectively. When a merging flow is not presented, the average movement time per floor is 15.1 s ± 0.8 s and 11.9 s ± 0.8 s for the ascent and descent movement. Under congested conditions, the average speeds on long stairwells maintains a relatively constant value of approximately 0.50 m/s ± 0.17 m/s, and 0.61 m/s ± 0.14 m/s for respective ascent and descent movement, while the traveling distance has no obvious impact on speed. Furthermore, the relationship between velocity and density in our observations is in line with linear functions and equations are accordingly proposed.

Effects of ERV Filter Degradation on Indoor CO2 Levels of a Classroom

Energy recovery ventilators (ERVs) are widely used to reduce energy losses caused by ventilation and improve indoor air quality for recently-constructed buildings. It is important for spaces with high occupancy density and longer residence times, such as classrooms. In classrooms, the ERV size is typically estimated by the target number of students in the design phase, but the design air volume flow rates (m3/h) of the ERV can decrease over time owing to filter degradation such as increased dust loading. In this study, field tests are conducted in a classroom to investigate filter degradation through a visual inspection and by measuring the air volume flow rates at the diffusers connected to the ERV. In addition, variations in carbon dioxide (CO2) concentrations are also measured to verify the effects of filter degradation on the indoor CO2 levels over the entire test period, which includes filter replacement, as well. As the tests are conducted during classes, several adjusting methodologies are proposed to match the different test conditions. The results show that the total air volume flow rate of the ERV increases after the filter replacement (546 to 766 m3/h), but it again decreases as time elapses (659 m3/h). Accordingly, the indoor CO2 concentration decreases after the filter replacement by more than 300 ppm (1404 to 1085 ppm), clearly showing the effect of filter degradation. However, this CO2 concentration remains similar for four months after the replacement, and the total air volume rate decreases again. An interpretation is made using computational fluid dynamics analysis that the measured CO2 concentrations are affected by airflow patterns. The airflow in the cooling system may dilute CO2 concentrations at the measuring location. Thus, periodic filter replacement and management are important to ensure the desired ERV air volume rates and consequently the desired indoor CO2 concentrations.

Thermal comfort improvement of naturally ventilated patient wards in Singapore

Located near the equator, Singapore has a tropical rainforest climate with high temperature and high humidity. In hospitals of Singapore, the subsidized patient wards are designed to be naturally ventilated, considering the affordability for patients. However, due to the high occupant density of the patient wards and the hot humid climate, occupants may feel discomfort, especially in the older hospital wards which were not well designed for natural ventilation. In this paper, the thermal comfort level of occupants at Singapore's Changi General Hospital (CGH) is evaluated based on both in-situ measurements and modeling analysis. Against this backdrop, several low energy solution concepts that potentially improve the thermal comfort level of occupants in patient wards are analyzed and simulated using detailed building thermodynamic and airflow simulation. We found that this approach of combining thermodynamics, computational fluid dynamics, and thermal comfort level models was effective for analyzing and comparing the thermal comfort impact of alternative, low-energy building retrofit concepts. We also found that passive solutions to ventilation could be used effectively for a patient hospital ward, even in the tropical warm climate of Singapore.