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People tend to spend considerable amounts of time in buildings; thus the issue of providing proper indoor environmental quality is of significant importance. This paper experimentally analyses the subjective sensations of the occupants of intelligent and traditional buildings with the focus on possible differences between these two types of buildings. The study is based on a large database of 1302 questionnaires collected in 92 rooms where simultaneous measurements of the indoor environment physical parameters (air and globe temperature, relative humidity, carbon dioxide concentration, and illuminance) were carried out. Their impact on the subjective assessment of the indoor environment has been presented and analysed. The results show that the occupants seemed to be more favourable towards the indoor conditions in the intelligent building; however, the differences in comparison to the traditional buildings were not considerable. Similarly, self-reported productivity proved to be higher in the intelligent building, while the optimal range of air temperature, which ensured highest productivity, was 22–25 °C. Moreover, a strong correlation between the occupants' overall comfort and their perception of the air quality has been found. [ABSTRACT FROM AUTHOR]

This field study aimed to investigate naturally ventilated bedroom environment and its effects on subjective perception and sleep quality. Totally, 104 healthy subjects living in urban areas of Beijing participated in the study for one night during transition seasons. Bedroom environment parameters, including temperature, relative humidity, and CO2 concentration, were recorded before and during sleep. Objective sleep quality was measured by Fitbit Alta 2, a wrist‐type actigraphy sensor. Subjective assessments were collected by paper‐based questionnaires on sleep quality and environmental perceptions. The results showed that neutral temperature for waking state (before sleep) was estimated to be 23.8°C while for sleep state it was 26.5°C. Furthermore, pre‐sleep thermal sensation vote was found to be positively correlated with deep sleep percentage. Indoor air quality was correlated with sleep quality as indicated by statistically significant correlations between odor intensity assessment, air quality acceptability, average nightly CO2 concentration, and measures of sleep quality. For naturally ventilated bedrooms during transition seasons with a mild outdoor climate, present findings suggest that a bedroom with slightly warm pre‐sleep environment than neutral, and with high ventilation as indicated by low indoor CO2 concentration, could be beneficial for sleep quality of residents. [ABSTRACT FROM AUTHOR]

Housing environment has become a driving factor on hen health, egg quality and efficient production in intensive poultry industry. In large layer poultry housing system, an environmental index is typically used to control air conditions, including air temperature (T), relative humidity (RH) and concentration of carbon dioxide (CO2) in different season. In hot seasons, thermal environment of laying hen housing is usually assessed using the temperature humidity index (THI) via the online monitored temperature and relative humidity. However, the simple assessment cannot meet the harsh requirement of indoor air quality in a large layer house, as the stocking density increases in recent years. In this paper, a comprehensive environmental index (CEI) was proposed based on the radar map to integrate the impacts of both thermal and air quality factors, in order to systematically assess the environment comfort of the birds. A LabVIEW software system was selected to illustrate the environmental comfort using the fuzzy mathematics. Five key environmental factors, including temperature, RH, air velocity, concentration of CO2 and ammonia (NH3), were used to evaluate the environmental comfort of laying hen housing, where the their weights were normalized in a radar map. In the visualized system, early warning can be delivered when either a single factor or the CEI was over the prescribed value, and thereby a quick action can be taken to adjust the environmental conditions in the layer housing to a comfort level. A field measurement was carried out at a commercial layer breeder farm in Hebei province from January to February, and from July to August, 2019. The experimental results indicated that a good performance of the CEI can be obtained to assess the comprehensive environment in the tested house via monitoring the five environmental indexes. The specific sensors were properly settled in the henhouse. The data of environmental conditions was collected to verify, and then the maximum of five indexes were selected for later use. During the summer daytime, the CEI agreed well with the THI, indicating the positive impacts of thermal environment on the comfort of the birds, while it performed better to integrate the thermal and air quality at night time. In winter, the increase in the weight of CO2 concentration can contribute to the CEI for the comfort in layer housing system. The in situ monitoring data in the actual use demonstrated that the CEI can efficiently represent the change of comprehensive environmental comfort in the chicken house, and respond to the interaction between environmental factors in each period, especially when the air quality has an increasing influence on the comprehensive environmental comfort at night in summer and in winter. The findings can provide a promising method to systematically evaluate the housing environment via the five key factors in laying hen housing, further to improve the birds comfort via precisely controlling the air conditions in intensive poultry production. [ABSTRACT FROM AUTHOR]

To investigate an air distribution system with the potential to provide a comfortable thermal environment and efficient ventilation performance in heating mode, this study compared the numerical results of the RNG k- ε model, realizable k- ε model and SST k-ω model with experimental data obtained from a typical office with wall confluent jets ventilation (WCJV) for heating. The SST k-ω model was chosen for numerical study of WCJV. The findings showed that the WCJV performed better than mixing ventilation (MV) in the heating mode because WCJV could entrain less ambient air and maintain the jets' momentum and energy to reach the occupied zone. The effects of supply air temperature difference (in the range of 2.00°C to 7.79°C) and supply air velocity (in the range of 2.20 m/s to 8.50 m/s) on the jet velocity profiles and ventilation performance of WCJV were also quantified. The results showed that the jet velocity profile was more sensitive to the supply air velocity than to the supply air temperature difference. Accordingly, reducing the supply air velocity might result in poorer thermal environment and air quality in the occupied zone because the warm air jets cannot spread out over the floor area. The results can be helpful in understanding WCJV used for ventilation under heating mode. [ABSTRACT FROM AUTHOR]

Abstract Ventilation is commonly thought to be helpful for improving indoor air quality. However, this may not be true when the outdoor air is polluted. For example, in the event of fog or haze in developing countries, outdoor particulate matter (PM) can be drawn into rooms by ventilation systems. In such circumstances, ventilation must be accompanied by indoor particle filtration. This investigation incorporated a particulate-filtration model into the EnergyPlus software. The validated software was then used to evaluate ventilation together with indoor particle filtration in a typical Chinese residential apartment. The ventilation modes included natural, mechanical, and hybrid ventilation. Transient air change rate, indoor CO 2 and PM2.5 concentrations, air temperature, annual energy consumption, and utility costs were solved. For the mechanical systems, demand-controlled outdoor air rates and clean air delivery rates (CADRs) that ensure acceptable indoor air quality were also solved. It was found that indoor particulate filtration must be utilized in northern Chinese dwellings. A combination of natural ventilation and portable demand-controlled particulate filtration has the lowest operating cost, but the ventilation rate may occasionally be insufficient. Among the mechanical ventilation modes, decentralized systems operating only during the occupied period have great potential to minimize utility costs. Mechanical ventilation in demand-controlled operation and its hybrid with natural ventilation can further reduce energy consumption. Highlights • A particle-filtration model was incorporated into EnergyPlus. • Demand-controlled outdoor air rates and CADRs ensuring air quality were solved. • Natural ventilation plus portable filtration cost least but provide insufficient outdoor air. • Decentralized mechanical systems operating only in the occupied period save utility costs. [ABSTRACT FROM AUTHOR]

This study assesses American Society of Heating, Refrigerating and Air-Conditioning Engineers Guideline 36 (G36) with a typical medium office building. Specifically, this study employed a Modelica model of a variable air volume (VAV) system that serves this building, which includes components for representing indoor virus transmission and filtration. It then implemented the G36 control sequences for both water-side and air-side equipment in Python. After that, this study conducted the assessment by co-simulating G36 and the Modelica model using the Building Operations Testing Framework. Unlike existing works, this work has three unique features: (1) It considers the interactions between control sequences for water-side and air-side equipment of the studied VAV system. (2) It assesses the performance of G36 from the perspective of IAQ. (3) It examines the short-term behaviors of the studied building under G36 to understand the control stability. This assessment confirms significant energy savings from G36, largely because of the interaction between supply air temperature and hot water controls. It also reveals a trade-off between the ability to slow the spread of virus and the energy performance via demand controlled ventilation. Lastly, it emphasizes the necessity of tuning local feedback control when implementing G36. • Evaluate interactions of air-side and water-side controls from Guideline 36. • Assess the performance of Guideline 36 considering IAQ under indoor virus scenarios. • Examine the control stability of Guideline 36 with high-fidelity dynamic models. • Energy performance may conflict with IAQ when using Guideline 36. • Local feedback control needs to be tuned to unleash the potential of Guideline 36. [ABSTRACT FROM AUTHOR]

The benefits of task ambient conditioning in improving thermal comfort and indoor air quality have been demonstrated in recent studies. The potential use of task ambient conditioning for improving thermal comfort when the room air temperature is beyond the suggested range in mixing ventilation; however, has not been fully explored. A newly developed task ambient conditioning with chest exposure was, therefore, suggested at the room air temperature of 28°C (82.4°F), which is higher than the normally set temperature under cooling conditions in mixing ventilation. The present study aims to explore the appropriate air parameter ranges of the local airflow, but not to develop the practical system. Assessments of the thermal environment were performed by subjective questionnaires under nine distinct conditions with task ambient conditioning with chest exposure as well as the ambient environment in a climate chamber. The thermal sensations under the nine conditions with task ambient conditioning with chest exposure were nearly thermal neutral or slightly cool, while a slightly warm sensation was experienced in an ambient environment. Thermal sensation votes indicated cooler sensations with a decrease in the temperature of the locally supplied air, and with an increase in the velocity of locally supplied air, as well as in the vent diameter. The locally supplied airflow of task ambient conditioning with chest exposure obviously improved thermal comfort, the percentage of discomfort was reduced to 20% or less. Furthermore, the appropriate ranges of airflow parameters (air temperature, air velocity, and vent diameter) of task ambient conditioning with chest exposure were demonstrated, to aid the practical development of task ambient conditioning with chest exposure systems. [ABSTRACT FROM PUBLISHER]

To investigate the variation of classroom environment during typical lecture hours, repeated field measurements and intervention experiments for indoor temperature were carried out in a typical class (95 min in duration, 0.32–0.39 person/m2 of occupants density) in a spring semester of a university in Beijing. Environmental data were recorded every 5 min, including indoor temperature, relative humidity and carbon dioxide (CO 2) concentration. Additionally, volatile organic compounds (VOCs) were sampled and indoor air quality (IAQ) were evaluated repeatedly. The results of field measurements showed the average air temperature in the classroom ranged from 21.2 ± 0.8 °C to 26.8 ± 0.7 °C, relative humidity ranged from 23.1 ± 1.8% to 57.5 ± 0.2%, and the average concentrations of CO 2 and total volatile organic compounds (TVOC) were 1,291–1,833 ppmv and 159-1,178 ppbm respectively. The subjective evaluations collected during intervention experiments showed that perceived odor intensity by visitors upon entering the room increased significantly, meanwhile the satisfaction and acceptability of air quality reduced considerably at the indoor temperature of 27 °C than that at 24 °C. Present results suggest when the indoor temperature rises, it is necessary to increase the outdoor air supply rate to ensure air freshness in classrooms. Subsequently, the calculated CO 2 emission rate by students increased by 0.54 L/h per person for every 1 °C rise in indoor temperature. Corresponding to the control target of indoor CO 2 concentration of 1,000 ppmv, the outdoor air ventilation rate required to eliminate occupant-generated pollution needs to be increased by 0.25 L/s per person. • The air quality in a classroom during typical lecture periods was investigated. • The CO 2 emission rate of college students was estimated using indoor CO 2 levels. • Perceived air quality was reduced significantly as indoor temperature increased. • Personal CO 2 emission rate increases by 0.54 L/h for 1 °C rise in temperature. • Higher outdoor air supply rate is recommended when indoor temperature rises. [ABSTRACT FROM AUTHOR]

Previous studies have shown that poorly ventilated classrooms can have negative impact on the health of children and school staff. In most cases, schools in Serbia are ventilated naturally. Considering their high occupancy, classroom air quality test determines the level of air pollution, after which it is possible to implement corrective measures. The research presented in this study, was conducted in four schools which are located in different areas and have different architecture designs. Measurements in these schools have been performed during the winter (heating season) and spring (non-heating season) and the following results were presented: indoor air temperature, relative humidity, and carbon dioxide concentration. These results show that the classroom average concentration of carbon dioxide often exceeds the value of 1500 ppm, during its full occupancy, which indicates inadequate ventilation. Measurement campaigns show that carbon dioxide concentration increased significantly from non-heating to heating season in three of the four schools. Analysis of measurements also determined high correlation between relative humidity and carbon dioxide concentration in all schools in winter season. This fact may constitute a solid basis for the fresh air supply strategy. [ABSTRACT FROM AUTHOR]

The aim of the Best Vent project was to find the optimal control strategy for demand-controlled ventilation (DCV) without compromising on indoor air quality. In this paper, we discuss control strategies that would ensure acceptable perceived air quality for unadapted users. This study is a part of a series of field studies where sensory panels of untrained persons visited classrooms at a school. The sensory panel visited classrooms occupied by different user groups, at different ventilation rates and temperatures, and in empty classrooms at different ventilation rates, and with different pollutant loads. This study aims to assess whether it would be reasonable to control the supply airflow rate towards a higher CO 2 setpoint at low air temperature, and still maintain the same perceived indoor air quality upon entry. The results indicate that the perception of indoor air quality does not deteriorate at higher CO 2 concentrations when the air temperature is kept at 21 °C as opposed to at 24 °C. Furthermore, an increase in air temperature yielded poorer perceived air quality scores at similar CO 2 concentrations in the classrooms. Our results indicate that a DCV-control strategy with a higher CO 2 setpoint in classrooms at low temperatures would not compromise perceived air quality. Further research would be needed to assess whether the same is true for indoor climate-related symptoms or performance. • Control strategies for demand-controlled ventilation are investigated. • The classrooms had two different levels of CO 2 and temperature. • Higher CO 2 setpoint at low temperatures will not compromise perceived air quality. • Perceived indoor air quality was assessed by an untrained sensory panel. [ABSTRACT FROM AUTHOR]

The internal partitioning, which is frequently introduced in open-space planning due to its flexibility, was tested to study its effects on the room air quality as well as ventilation performance. For the study, physical tests using a small model room and numerical modeling using CFD computation were utilized to evaluate different test conditions employing mixing ventilation from the ceiling. The partition parameters, such as its location, height, and the gap underneath, as well as contaminant source location were tested under isothermal conditions. This paper summarizes the results from the study. [Copyright &y& Elsevier]

As most residents spend more than 90% of their time in buildings, acceptable and reasonable control of both indoor thermal comfort and air quality is imperative to ensure occupants' health status and work productivity. However, current control strategies generally take either thermal comfort or indoor air quality as a single loop, rather than the concurrent control of two. To analyze their mutual influence, this study investigated the performance of three multi-control approaches, i.e., proportional integral derivative (PID) control of thermal comfort and a fixed outdoor air ratio, PID control of thermal comfort and design outdoor air rate, and PID control of thermal comfort and occupancy-based demand-controlled ventilation. As a pilot study, three typical control methods were implemented to a multi-zone building via OpenModelica modeling. The results indicate that indoor air temperature can be well-maintained under three control methods, however, the CO2 concentration under the fixed outdoor air ratio was over 1000 ppm, leading to poor indoor air quality. The control strategy with the design outdoor air rate could not properly ensure the CO2 concentration, due to the over-ventilated or under-ventilated phenomena, subsequently resulting in unnecessary energy waste. The occupancy-based demand controlled ventilation could maintain the CO2 concentration under the set-point with an intermediate power energy utilization. [ABSTRACT FROM AUTHOR]

Indoor air quality and thermal conditions are important considerations when designing indoor spaces to ensure occupant health, satisfaction, and productivity. Carbon dioxide (CO2) concentration and indoor air temperature are two measurable parameters to assess air quality and thermal conditions within a space. Occupants are progressively affected by the indoor environment as the time spent indoors prolongs. Specifically, there is an interest in carrying out investigations on the indoor environment through surveying existing Heating, Ventilation, Air Conditioning (HVAC) system operations in classrooms. Indoor air temperature and CO2 concentration in multiple lecture halls in Toronto, Canada were monitored; observations consistently show high indoor air temperature (overheating) and high CO2 concentration. One classroom is chosen as a representative case study for this paper. The results verify a strong correlation between the number of occupants and the increase in air temperature and CO2 concentration. Building Energy Simulation (BES) is used to investigate the causes of discomfort in the classroom, and to identify methods for regulating the temperature and CO2 concentration. This paper proposes retro-commissioning strategies that could be implemented in institutional buildings; specifically, the increase of outdoor airflow rate and the addition of occupancy-based pre-active HVAC system control. The proposed retrofit cases reduce the measured overheating in the classrooms by 2-3 °C (indoor temperature should be below 23 °C) and maintain CO2 concentration under 900 ppm (the CO2 threshold is 1000 ppm), showing promising improvements to a classroom's thermal condition and indoor air quality. [ABSTRACT FROM AUTHOR]