Indoor Environmental Parameters Research Articles

How to investigate differences in indoor environmental comfort and adaptation? Mixed methods research with patients

ABSTRACT Ensuring hospitalized patients’ comfort requires understanding differences in comfort and adaptation to discomfort, as well as the role of the built environment therein. Shortcomings in this understanding result from limitations of existing research methods. Therefore the potential of a mixed methods research design to investigate when and why experiences of and adaption to (dis)comfort differ among hospitalized patients was explored. A convergent mixed methods case study was conducted in two hospital wards of a Belgian hospital. Qualitative data included interviews with 19 patients about their experiences and information about the patients at the two wards during the fieldwork; quantitative data included sensor measurements of indoor environmental quality parameters (i.e. illuminance and indoor temperature), a questionnaire among 238 patients about their assessment of the indoor conditions, and simulations of these conditions. Joint displays allowed comparing situations in which characteristics related to the patients or their setting differed in an integrated way. The displays provide an intermediate step between purely qualitative descriptions of comfort and adaptation and purely quantitative models that predict both. Scenarios that the joint displays allow identifying inform about characteristics that could improve these models, and about roles of the built environment in experiences.

Household indoor air quality in northeast China: On-site inspection and measurement in 399 Tianjin area residences

There has been an increased concern on indoor air quality (IAQ) in residences since the majority of individuals’ time is mainly spent indoors. We inspected and measured indoor environmental parameters in 399 homes in northeast China in order to study IAQ. We systematically measured multilevel environmental parameters (physical, chemical, and biological) in children’s bedrooms during all seasons. The results indicated that the median values for indoor temperature, relative humidity, total volatile organic compounds (TVOC), and formaldehyde concentrations throughout the year were within the Chinese national standards. However, the median carbon dioxide concentrations exceeded 1000 ppm during spring, autumn, and winter. In the same seasons, the air change rate (ACR) was below the minimum required level of 0.5 h−1. Di-2-ethylhexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), and di-isobutyl phthalate (DiBP) were predominantly detected in settled dust, displaying median concentrations of 126.9, 41.5, and 16.3 μg/g, respectively. Notably, phthalate concentrations were significantly higher in urban houses as compared to rural houses. Furthermore, median concentrations of Dermatophagoides farinae (Der f) and endotoxin were 689.4 ng/g and 3689.1 EU/g, respectively, trending higher in winter than summer. There was a negative correlation between ACR and chemical pollutants (TVOC, formaldehyde, and DiBP). In conclusion, northeast Chinese homes had poor indoor air quality with ubiquitous exposure to modern chemical compounds and insufficient ventilation.

Influence of window and door opening on office room environment and human thermal sensation during different seasons in moderate climate

Natural ventilation is commonly used in buildings because it does not require energy, and its various strategies, for example ventilation through an open window, can improve the indoor environment quality, including the thermal comfort of users. This study aimed to determine accurate environmental parameters typical for naturally ventilated rooms for three seasons: summer, autumn and winter, and to assess the occupants' thermal sensation in the mentioned conditions. Based on the measurements, the spatial distribution and time variability of air temperature and air speed in an office room with a stack natural ventilation system were assessed. The resulting data on the indoor environment parameters at different seasons and with various door and window opening configurations were used as an input to simulate human thermal sensation. Three models were used for simulation: predicted mean vote (PMV), the thermal sensation (TS) model developed by Zhang et al., and the advanced dynamic thermal sensation (DTS) model by Fiala et al., which allowed the demonstration of differences in the thermal comfort assessment depending on the method. Measurements have shown that opening the window with the door closed has a negligible impact on the parameters indoor environment parameters in summer; opening the door (cross-ventilation) changes this situation. The effect increased during autumn and winter, which affects users' thermal sensations. The assessment based on the most popular PMV model differed from the indications of advanced DTS and TS models showing significant discrepancies, which may lead to a misinterpretation of thermal comfort for individuals in the room.

Field Investigation on Adaptive Thermal Comfort in Rural Dwellings: A Case Study in Linyi (China) during Summer

A large number of people in China still live in rural villages. The indoor environment of these rural dwellings directly affects the quality of life of the occupants. Nevertheless, constrained by the quality of dwelling construction, rural buildings have poorer indoor environments and, at the same time, have a higher operating energy consumption. However, inadequate attention has been given to the summer thermal environment in cold regions. This work has been carried out around the thermal environment of rural residences in cold regions during summer. Field measurements, questionnaires, and data analysis were used in this study. We recorded the indoor and outdoor thermal environment parameters on a typical summer day in the Linyi rural area. Moreover, the subjective sensations and thermal adaptive behaviors of the participants were recorded in detail with a questionnaire. Linear regression showed that the neutral temperature for residents in summer was 27.52 °C, with acceptable temperatures ranging from 25.14 °C to 29.9 °C. Age and gender differences were found to affect the occupants’ sensation of thermal comfort and humidity, as well as their thermal adaptive behavior. In addition, a thermal adaptive model has been constructed in the study, which will further enrich the thermal adaptive investigation and provide a scientifically sound reference for the renovation and development of the local rural areas.

Indoor air quality prediction modeling for a naturally ventilated fitness building using RNN-LSTM artificial neural networks

Indoor air quality prediction modeling for a naturally ventilated fitness building using RNN-LSTM artificial neural networks

A dynamic ventilation strategy for industrial buildings based on weight factors

In industrial buildings, pollution sources are often multi-point and unstable. This study proposes a dynamic exhaust strategy (DES) that aims to balance energy utilization efficiency and system performance without the need for monitoring indoor environmental parameters. Firstly, the DES system only monitors the local pollutant concentration in each outlet to determine its “exhaust potential”. Weight factors are then assigned to adjust the total exhaust flowrate, achieving real-time dynamic weight allocation (DWA) and improving the system performance in removing pollutants. Secondly, the system monitors the total pollutants removal from all outlets to enable dynamic total exhaust flowrate adjustment (DTA) to reduce energy consumption. A stochastic release model of multiple pollution sources was established in a typical thermally polluted workshop, and numerical simulations were conducted to investigate the effects of factors such as the stochastic non-uniformity of sources release, frequency and range of dynamic parameter adjustments, and energy-saving potential of the DES system. The results indicate that the DES system demonstrates increased effectiveness in pollutants removal as the randomness of the sources release increases, with a 12 % improvement in capture efficiency η compared to the unregulated system. Additionally, by utilizing 80 % of the total exhaust flowrate to adjust it at a frequency of 5 s per time in the DWA process, the system can meet requirements for pollutants removal, performance, and stability. Furthermore, the co-regulation of the DWA and DTA processes can reduce energy consumption by 78 % while maintaining an 81 % capture efficiency compared to using the DWA alone.

Comparison of thermal comfort between different heating systems and adaptation to different indoor climates in winter.

Individual heating systems, such as the air-source heat pump (ASHP) air-conditioner or floor heating (FH), are usually used by people living in the hot summer and cold winter (HSCW) zone of China to heat indoor climates in the winter. However, little research has been conducted in the HSCW zone on the thermal comfort difference between indoor climates heated by ASHP air-conditioners and those heated by floor heating, as well as how occupants adapt to different indoor climates. We conducted a comparative field experiment in ASHP-heated and FH-heated apartments in Nanjing to investigate how different types of heating systems influence the thermal sensation of occupants, and we conducted a comparative field experiment in ASHP-heated office buildings and naturally ventilated teaching buildings in Shanghai to investigate how occupants adapt to different indoor thermal environments. Indoor environmental parameters and body surface temperatures were measured using instruments, and occupants' thermal sensation, activity level, and clothing were evaluated using the questionnaire. The results show that floor heating improves thermal comfort by raising foot temperature compared to the ASHP air-conditioner, and that occupants become acclimatized to different indoor climates by adjusting neutral operative temperature. According to the findings, there is no need to overheat the indoor environment in the HSCW zone because occupants can adapt to their experienced thermal environment and it is critical to maintain warm foot temperature in the cool/cold indoor environment.

Effects of indoor environment on EEG and thermal comfort under the ceiling-fan-integrated air conditioning system

This study investigated the correlations between the relative EEG power at different frequency bands under ceiling-fan-integrated air conditioning (CFIAC) systems. Twenty subjects participated in the experiments with the combinations of five air temperature levels (24, 25, 26, 27, and 28 °C) and six ceiling fan gears (Levels 1, 2, 3, 4, 5, and closed). The EEG signals and indoor environmental parameters (relative humidity, air velocity, and temperature) were recorded synchronously, and the thermal comfort online survey for each subject was obtained as well. The most comfortable combination was found when the air temperature was 27 °C and the fan speed was 0.3 m/s. When the air temperature was 25 °C, the relative EEG power in the different bands was least distinguishable, but when the temperature rose to 27 °C, it occurred an obvious change in different lobes. The δ, θ, β, and γ-bands significantly correlated with indoor setting temperature for the whole brain, but only the θ-band located at the occipital lobe significantly correlated with ceiling fan speed. The significance for the α-band with setting temperature and the β-band signal with air velocity varies with the subjects. Compared to the common air conditioning (CAC) system, CFIAC had a different effect on the relationship between relative EEG power and exposure environment. The airflow due to the ceiling fan may reverse this relationship between α-band, β-band, and IAT from positive (CFIAC system) to negative (CAC system). This study can contribute to developing wearable sensing data-driven thermal comfort evaluation models.

Exploring the influence of indoor environment and spatial layout on changed behaviours of people with dementia in a nursing home

People with dementia sometimes show changed behaviours such as agitation, hallucination, and wandering during the moderate and severe dementia stages. In addition to individual health factors, contextual factors, such as indoor environment conditions, spatial layout, and human activities, may trigger or influence these behaviours, but there is a lack of solid evidence. We used mixed methods to collect data, including the fly-on-the-wall method to observe the residents' daily lives and deploying environmental sensors to monitor the indoor environments of two central living rooms and ten bedrooms in a nursing home in the Netherlands. A data collection campaign from August to September 2022 focused on the indoor environmental parameters, ventilation control of monitored rooms, the observation of ten participants' locations, activities, clothing levels, and changed behaviours. The data were analysed using Fisher's exact tests and heatmap analysis. The results show that even though the nursing home was well maintained according to existing indoor environmental quality standards, the room conditions of temperature, TVOC, and HCHO levels and contextual factors (main activity and numbers of people in the space) were significantly correlated with locations of changed behaviours. By analysing observation data with spatial layout, participants had larger activity ranges on the days that exhibited changed behaviours than those without. Most of these behaviours were observed at the edge of common spaces, where caregivers need to pay more attention.

Research on the Effect of Spray Ventilation Cooling Systems on Human Physiological and Psychological Indexes

Hot working environment not only affects work efficiency, but also poses a potential threat to the physical and mental health of staff. The current common method for dealing with high temperatures is spray-only or ventilation-only. To investigate the impact of different spray and ventilation modes on indoor high-temperature environments, this study examined their effects on indoor environmental parameters, average skin temperature, and psychological indicators. By establishing an experimental platform for high-temperature thermal environments, a spray ventilation cooling system was implemented, and its cooling efficacy in the indoor thermal environment was analyzed. The environmental classification of the high-temperature working environment under experimental conditions is provided based on the experimental data. A comparison and analysis of environmental parameters and physiological and psychological indicators between moderate and high-temperature environments were conducted. The combination of spray and ventilation modes resulted in a 5.3 °C reduction in air temperature, a 24.1% increase in average relative humidity, and a 3.3 °C reduction in average Wet-bulb Globe Temperature (WBGT). The cooling effect was increased by 2.3 °C and the average relative humidity was increased by 10.8% compared to spray-only and ventilation-only modes. In spray and ventilation mode, when the spray volume is increased by 15 mL/min, the air temperature is reduced by 8.2 °C, the average relative humidity is increased by 31.9%, and the average WBGT is reduced by 5.1 °C. This study has guiding significance for finding a reasonable cooling scheme to cope with indoor high-temperature environments.

Optimization of university timetables considering students’ thermal sensation in classrooms

In northern China, university classrooms are often densely populated, and students have limited means of thermal adaptation during lectures. Considering the significant differences in the thermal environment of the classroom throughout different periods, changing the patterns of classroom utilization is a feasible way to improve students’ thermal comfort during classes and ensure learning efficiency. A university teaching building in Xi'an is considered an example in this study. The indoor and outdoor thermal environment parameters of the teaching building were measured in the autumn semester, and the students’ thermal sensation was investigated. On this basis, a model for optimizing university timetables was developed to minimize students’ thermal discomfort in classrooms. The study results showed: 1) During non-heating seasons, students felt comfortable in all periods, except for the third class period (14:00–15:30), during which they felt slightly hot. During the heating season, students felt slightly cold in the first class period (8:30–10:00), slightly hot in the third class period, and comfortable in the second (10:30–12:00) and fourth (16:00–17:30) class periods. 2) Compared to the general schedule, the optimized timetable decreased first period classes by 14 and increased fourth period classes by 13, with minimal changes elsewhere. Adopting this approach, students’ thermal discomfort time during classes in the autumn semester was shortened by 6.16%. 3) The students’ thermal discomfort time reduction rate obtained by timetabling optimization during the non-heating season, heating season are 0.78%, 8.91%, respectively. The effect of reducing students’ thermal discomfort is more pronounced during the heating season.

Scoping review of post occupancy evaluation of office buildings with focus on indoor environmental quality and productivity

Post occupancy evaluation (POE) is used widely to evaluate if a building performs as envisioned during the design phase, and more importantly, if the occupants feel healthy and well. The aim of the present study was to review the practices of post occupancy evaluation in office buildings and assess how they evaluated indoor environmental quality (IEQ) and productivity/performance. This was done using a systematic literature search process. A total of 136 papers summarising the findings of 116 studies were included. The studies were analysed according to study type, country, number of buildings, study purpose and objective, applied methods, indoor environmental quality parameters, occupant responses, and productivity/performance assessment. The findings suggest that there is no overall “one-size-fits-all” post occupancy evaluation protocol dominating the assessment of office buildings. The methods and practices varied between studies but questionnaires to the occupants were used consistently; many of the questionnaires were inspired by existing survey schemes. The assessed indoor environmental quality parameters also varied between studies and depended on the purpose of the specific study. Productivity or performance was evaluated in approximately 1/3 of the studies, primarily by self-reported assessment via the questionnaire. Major shortcomings identified were the uncertainties associated with the performance assessment, how to put the findings into practice, and how to assess the cost-benefit of the findings.

Effects of thermal-acoustic interaction on airport terminal's indoor thermal comfort: A case study in cold region of China

Airport terminals are typical large-scale public buildings. Improving the indoor environment of the terminal plays an important role in increasing users' comfort status. In this study, we chose Xianyang Airport Terminal 3 and conducted field tests and questionnaire surveys to obtain indoor environmental parameters and subjective perceptual evaluations. By comparing the correlations between the two aspects, we made analyses about the interaction effects of thermal-acoustic environments on people's indoor thermal comfort. The results show that there are significant correlations between TSV and the temperature, SSV and the sound level. The neutral temperatures of MB and CB are 19 °C and 21 °C, respectively. TCV are mostly above 0, but when the temperature reaches a certain state, it would decrease rapidly. Most of the participants hasn't showed strong feelings of comfort or discomfort, which revealed a relatively high tolerance and adaptation to the indoor environment. As the summer is hot and humid, setting the indoor temperature at 24 °C would be a balance between cost and comfort. The overall sound level is loud, which decreased the TCV to a certain extent while the tendency of how thermal comfort changes remains the same. According to different characteristics of the space, various passive and active approaches were suggested to improve the thermal and acoustic environment. This study partly agrees with the previous studies and we hope to provide reference for the optimization of summer indoor environment in large-scale public buildings in similar climate and location.

An empirical study of indoor air quality in badminton stadiums in hot summer and cold winter regions of China during spring and fall seasons

The indoor air quality has a direct impact on human health. In order to obtain the current status of indoor air quality in typical sports buildings in hot summer and cold winter climate zones in China, indoor badminton courts in 10 cities in Hubei Province in this climate zone were selected as research objects for field testing of indoor environmental parameters in spring and autumn, and predict air quality parameters for non-testing times. All the tested stadiums are naturally ventilated in non-event conditions, and the average daily indoor CO2 concentration was 526.78 ppm in spring and 527.63 ppm in autumn, and the average daily PM2.5 concentration was 0.035 mg/m3 in spring and 0.024 mg/m3 in autumn, all of which met the requirements of GB/T 18883-2022, the average concentration of CO2 ≤ 1000 ppm and PM2.5 ≤ 0.05 mg/m3. The indoor CO2 concentration and PM2.5 concentration of the tested badminton halls under natural ventilation gradually increased with the accumulation of exercise time, making the indoor air quality of the badminton halls decrease, which would negatively affect the health of the people exercising in this environment.

Factor analysis and risk assessment of indoor environmental parameters and TSV in fitness centres under different zones, exercise intensities and times

Maintaining regular physical exercise is essential for maintaining good health. In China, fitness centres are thriving, and the cleanliness of the exercise environment has become increasingly important. This study investigated the thermal response and indoor air environment of fitness personnel in various areas of a fitness centre using subjective evaluation and on-site air environment measurements. The findings revealed that the indoor air environment in different exercise areas of the fitness centre varied spatially, which can lead to discomfort amongst fitness personnel during exercise. Overall, the thermal sensation in different areas of the fitness centre was found consistently too hot. Temperature and humidity have the greatest impact on the thermal sensation of individuals in different areas, while indoor air pollutants have a minimal effect. The intensity and duration of exercise can also influence the body’s heat sensation and pollutant inhalation dose. The body’s heat balance mechanism can affect subjective evaluations. This study proposes three strategies for optimizing the indoor environment of fitness centres through principal component analysis. This paper provides data and a methodological framework for the development of specifications supporting the design, operation and management of the environment in fitness centres.

Operating characteristics and evaluation of air source heat pumps in cold regions during heating season in China

The mismatch between the actual heat production of an air source heat pump (ASHP) and the instantaneous load of the building it heats is a critical cause of low energy efficiency. Research on the measured heating effect provides an effective approach to improve the energy efficiency of an ASHP. This study therefore focused on two small office buildings to explore the operating data describing the ASHP system source and load sides during the heating season. A sensitivity analysis was employed to explore the actual operational effects of the ASHP. Common problems associated with system operation were comprehensively identified, including the operation characteristics, energy efficiency coefficients, load characteristics, and energy consumption characteristics of the transmission and distribution systems. The effects of these problems were evaluated from three perspectives: integrated part load value (IPLV), system performance loss, and indoor environmental parameters. The results shows that the highest coefficient of performance (COP) of the ASHP in Building A was 3.27 while the IPLV was 2.68, operating status reached the standard. The COP value of the ASHP in Building B was 1.55 while the IPLV was 2.45. Poor value shows the low performance in operating phase, which can be further optimised by matching the building instantaneous load to the heat production of the ASHP, improves the operating effect of two buildings comprehensively.

Understanding university students’ perceptions of classroom environment: A synergistic approach integrating grounded theory (GT) and analytic hierarchy process (AHP)

University classrooms play a crucial role in students' educational experience, as they spend a significant amount of time in these spaces. Understanding students' perceptions of the classroom environment is essential for improving classroom design and management. Adopting a user-centric approach, a novel research design combining both qualitative and quantitative research methods is employed to develop and validate an evaluation framework for classroom environment evaluation. Specifically, this study utilises grounded theory (GT) methodology to identify and prioritises the indoor environment parameters that students consider important. A classroom environment performance evaluation framework for the classrooms within a Hong Kong university was then developed based on the qualitative findings using the Analytic Hierarchy Process (AHP) method. The framework was then used to examine students' perceived importance of the university classroom performance among different sub-groups. The findings reveal that “facilities and services” emerged as the most critical parameter, emphasizing the importance of effective post-occupancy management. Intriguingly, there are minor differences in importance rankings between genders and education levels, with males emphasizing “indoor air quality” and females prioritizing “thermal comfort”. Moreover, distinct priorities are observed between various classroom types; students in lecture theatres focus on “seating plans” and “temperature”, while those in general classrooms prioritise “seating layout” and “fire safety”. These findings emphasise the need for effective post-occupancy management, while also highlight nuanced preferences based on gender, education levels, and classroom types, thereby offer crucial insights for designers to tailor indoor environments that better align with diverse student needs and preferences. Furthermore, a human-built environment interaction model is developed to summarise the research findings and provide insights for future research directions. This comprehensive approach enhances understanding of students’ preferences and experiences in university classrooms.

European residential ventilation: Investigating the impact on health and energy demand

The fundamental goal of building ventilation is to provide indoor conditions conducive to occupant health with low energy use. However, given the dynamic interplay of indoor and outdoor environmental conditions, there is limited knowledge on benchmarking human health and energy performance in relation to different ventilation systems. We coupled outdoor air pollution and meteorological data from 9 European cities with building energy simulations to investigate the effect of residential ventilation on indoor air quality, Disability-Adjusted Life Years (DALYs), and energy demand. Examining five representative ventilation systems, each operating under three distinct ventilative cooling (VC) scenarios, our findings reveal that PM2.5 accounted for the majority of DALYs (∼94 %). Filtering outdoor air in accordance with the standards reduced DALYs on average by ∼37 %. In the presence of filtration, VC based on indoor-outdoor temperatures increased DALYs by ∼10 %. However, a more comprehensive VC control based on both indoor-outdoor temperatures and outdoor air pollution did not increase DALYs. Overall, demand-controlled mechanical ventilation with energy recovery, outdoor air filtration, and VC resulted in the lowest energy demand and DALYs. Our results suggest that considering both indoor and outdoor environmental parameters can improve the performance of residential ventilation in terms of health and energy.

Enhancing real-time nonintrusive occupancy estimation in buildings via knowledge fusion network

Real-time nonintrusive occupancy estimation can maximize the use of existing sensors to infer occupant information in buildings with the advantages of fewer privacy concerns and fewer extra device costs. Recently, many deep learning architectures have proven effective in estimating occupancy directly from raw sensor data. However, some handcrafted features manually extracted from statistical and temporal domains might convey additional information for occupancy estimation. In this study, a novel knowledge fusion network for nonintrusive occupancy estimation is proposed to integrate knowledge from two streams, i.e. automatic knowledge stream from a deep learning architecture and handcrafted knowledge stream from manual feature engineering. Moreover, four different fusion modules are investigated to optimize the design of the fusion network. To verify the effectiveness of the proposed network, experiments are conducted in a dataset from the ASHRAE Global Occupant Behavior Database, which is collected from an office space with records of indoor environment parameters, occupant-building interactions, and contextual information. The results demonstrate the superiority of the proposed fusion network, which outperforms five representative algorithms. Furthermore, the ablation study underscores the benefits of knowledge fusion and occupant-building interaction information, showing that the proposed fusion network can enhance the occupancy estimation accuracy by 3.47 % to 9.24 %.

Performance Comparison of Indoor Humidity Modeling: A Novel Hybrid Model vs. the Simplified Calculation Model by EN ISO 13788

Ventilation is essential for maintaining indoor air quality and human comfort, particularly in buildings with mechanical ventilation systems. However, modeling the complex relationship between ventilation rate and measurable indoor environmental parameters, such as humidity, poses significant challenges. Current methods for modeling this relationship are often inefficient. For example, data-driven models frequently require sufficient information on ventilation, which may not be available for constant air volume (CAV) systems. On the other hand, simulation programs can be time-consuming and require expert engagement. In this study, we present two simplified calculation models, including a hybrid model developed by the authors, and a well-known model introduced by EN ISO 13788. We compare their performance in evaluating the impact of ventilation rate on indoor humidity. The hybrid model uses a novel analytical method to upgrade a single-input regression model (which considers only outdoor humidity as input) to enable the evaluation of indoor humidity based on both outdoor humidity and ventilation rate. We used the commercial TRNSYS program to model two scenarios: increasing the reference ventilation rate and decreasing the reference ventilation rate. The results showed that both models matched TRNSYS simulations with satisfactory accuracies, but the hybrid model demonstrated superior performance to the EN ISO 13788 model in both scenarios. The hybrid model’s higher accuracy and hybrid features make it better suited for big data analysis and field studies.