The present paper shows the results of a literature survey aimed at exploring how the indoor environment in buildings affects human comfort. The survey was made to gather data that can be useful when ...new concepts of controlling the indoor environment are developed. The following indoor environmental conditions influencing comfort in the built environment were surveyed: thermal, visual and acoustic, as well as air quality. The literature was surveyed to determine which of these conditions were ranked by building users as being the most important determinants of comfort. The survey also examined the extent to which other factors unrelated to the indoor environment, such as individual characteristics of building occupants, building-related factors and outdoor climate including seasonal changes, influence whether the indoor environment is evaluated as comfortable or not. The results suggest that when developing systems for controlling the indoor environment, the type of building and outdoor climate, including season, should be taken into account. Providing occupants with the possibility to control the indoor environment improves thermal and visual comfort as well as satisfaction with the air quality. Thermal comfort is ranked by building occupants to be of greater importance compared with visual and acoustic comfort and good air quality. It also seems to influence to a higher degree the overall satisfaction with indoor environmental quality compared with the impact of other indoor environmental conditions.
In this study, we examined changes in EEG signals during the cognitive activity at different air temperatures and relative humidities (RH). Thirty-two healthy young people acclimatized to the ...subtropical climate of Changsha, China, were recruited as subjects. They experienced four air temperature levels (26, 30, 33, and 37 °C) and two relative humidity levels (50 and 70%) in a climate chamber. During 175 min-long exposures to each thermal condition, they performed cognitive tasks and their EEG signals were measured. Relative humidity of 70% and increased temperature at this relative humidity significantly increased the relative power of δ-band and significantly decreased relative power of θ-band, α-band, and β-band. This may suggest that subjects were more sleepy but less drowsy, and it was more difficult for them to think clearly. At the same time, subjective evaluations indicated that they could be less alert and it was harder for them to think. However, no changes in performance of tasks measuring cognitive abilities were observed. It remains therefore unclear whether EEG can be a credible marker of changes in cognitive activity as a result of changes in indoor environmental quality in buildings and the future experiments should closely examine this issue.
Energy conservation in buildings as a way to reduce the emission of greenhouse gases is forcing an urgent re-examination of how closely thermal and air quality conditions should be controlled in ...buildings. Allowing conditions to drift outside the optimum range would conserve very large amounts of energy and would in most cases have only marginal effects on health or subjective comfort. The question that then arises is whether occupant performance would be negatively affected and if so, by how much. This information is required for cost-benefit analyses. The answers in this paper are based on laboratory and field experiments that have been carried out since the massive increase in energy costs that took place in the 1970s. Although only a few of the mechanisms by which indoor environmental effects occur have been identified, it is already clear that any economies achieved by energy conservation will be greatly exceeded by the costs incurred due to decreased performance. Reducing emissions by allowing indoor environmental conditions to deteriorate would thus be so expensive that it would justify greatly increased investment in more efficient use of energy in buildings in which conditions are not allowed to deteriorate. Labour costs in buildings exceed energy costs by two orders of magnitude, and as even the thermal and air quality conditions that the majority of building occupants currently accept can be shown to reduce performance by 5–10% for adults and by 15–30% for children, we cannot afford to allow them to deteriorate still further.
•Thermal and indoor air quality effects on the performance of office work and schoolwork are reviewed.•Thermal conditions and indoor air quality do affect the performance of office work and schoolwork.•Mechanisms underlying the observed effects are reviewed.•Thermal conditions and indoor air quality tend to affect performance “across the board”.
Human subjects were exposed for 3 h in a climate chamber to the air temperature of 35 °C that is an action level, at which the working time needs to be diminished in China. The purpose was to put ...this action level to test by measuring physiological responses, subjective ratings and cognitive performance, and compare them with responses at temperature of 26 °C (reference exposure). Moreover, CO2 was increased to 3000 ppm (CO2 exposure) at 35 °C to further examine, whether this change will have any effect on the measured responses. Compared with the reference exposure, exposure to 35 °C caused subjects to report feeling uncomfortably warm, to rate the air quality as worse, to report increased sleepiness and higher intensity of several acute health symptoms. Eardrum temperature, skin temperature, heart rate and body weight loss all increased significantly at this exposure, arterial oxygen saturation decreased significantly, while the percentage of adjacent inter-beat cardiac intervals differing by > 50 m (pNN50) decreased significantly, indicating elevated stress. The performance of addition and subtraction tasks decreased significantly during this exposure, as well. Increasing CO2 to 3000 ppm at 35 °C caused no significant changes in responses. Present results reaffirm the selection of 35 °C as an action level, and show that concurrently occurring high CO2 levels should not exacerbate the hazards.
•Subjects were exposed in a chamber for 3 h at elevated temperature and CO2.•Physiological and subjective responses and cognitive performance were examined.•Exposure to 35 °C increased health symptoms and discomfort and reduced performance.•3000 ppm CO2 at 35 °C did not exacerbate the negative effects of high temperature.•The results provide useful basis for protection of workers at high temperatures.
Thermal comfort, self‐reported acute health symptoms, cognitive performance, and physiological reactions were examined at four temperatures (26, 30, 33, and 37°C) at a relative humidity of 70%. ...Thirty‐two sub‐tropically acclimatized subjects experienced each condition for 175 minute, in balanced order, in a climatic chamber. The perception of heat gradually increased with increasing temperature, but the subjects felt hot only at 37°C. The temperature of 33°C was on average rated as acceptable and only just uncomfortable. The acceptability of air quality decreased linearly with increasing temperature. The intensity of acute health symptoms reported by the subjects increased with increasing temperature, but it was no more than moderate even at the highest temperature; dryness of skin and eye were alleviated. The eardrum temperature, skin temperature and moisture, heart rate, end‐tidal carbon dioxide, and weight loss increased significantly with increasing temperature, whereas the percentage of adjacent heart inter‐beat intervals differing by >50 ms decreased significantly. These results suggest that the perceived heat, self‐reported symptoms, and physiological reactions occurred concurrently. They show additionally that acclimatization to heat may shift the boundary of thermal discomfort to a higher temperature. The role of psychological adaptation and of the contextual aspects of this process still requires clarification in future experiments.
Human-emitted volatile organic compounds (VOCs) are mainly from breath and the skin. In this study, we continuously measured VOCs in a stainless-steel environmentally controlled climate chamber (22.5 ...m3, air change rate at 3.2 h–1) occupied by four seated human volunteers using proton transfer reaction time-of-flight mass spectrometry and gas chromatography mass spectrometry. Experiments with human whole body, breath-only, and dermal-only emissions were performed under ozone-free and ozone-present conditions. In addition, the effect of temperature, relative humidity, clothing type, and age was investigated for whole-body emissions. Without ozone, the whole-body total emission rate (ER) was 2180 ± 620 μg h–1 per person (p–1), dominated by exhaled chemicals. The ERs of oxygenated VOCs were positively correlated with the enthalpy of the air. Under ozone-present conditions (∼37 ppb), the whole-body total ER doubled, with the increase mainly driven by VOCs resulting from skin surface lipids/ozone reactions, which increased with relative humidity. Long clothing (more covered skin) was found to reduce the total ERs but enhanced certain chemicals related to the clothing. The ERs of VOCs derived from this study provide a valuable data set of human emissions under various conditions and can be used in models to better predict indoor air quality, especially for highly occupied environments.
The effects on human performance of elevated temperature causing thermal discomfort were investigated. Recruited subjects performed neurobehavioural tests examining different component skills, and ...addition and typing tasks that were used to replicate office work. The results show that thermal discomfort caused by elevated air temperature had a negative effect on performance. A quantitative relationship was established between thermal sensation votes and task performance. It can be used for economic calculations pertaining to building design and operation when occupant productivity is considered. The relationship indicates that optimum performance can be achieved slightly below neutral, while thermal discomfort (feeling too warm or too cold) leads to reduced performance. Consequently, it makes sense to set the PMV limits in workplaces in the range between −0.5 and 0 instead of between −0.5 and 0.5 as stipulated in the present standards.
All existing thermal comfort standards are applicable to naturally ventilated buildings and air-conditioned buildings, except mixed-mode buildings. Split air-conditioned buildings, as a type of ...mixed-mode buildings, account for a large proportion of current buildings. It is urgent to explore the applicability of thermal comfort standards and determine the energy saving potential in split air-conditioned buildings. In this research, the authors conducted a field study in Changsha, China. Eleven split air-conditioned office buildings were investigated from July to September 2016. 442 valid data sets were obtained. The results indicated that occupants preferred a “cooler” temperature of 26 °C, 0.6°Clower than neutral temperature of 26.7 °C. Occupants have adapted to thermal environment and accepted higher temperature than that predicted by PPD. 95% of occupants were satisfied with the thermal environment. Compared to PMV model, the adaptive model was more applicable to split air-conditioned buildings. 8.6% of cooling energy could be conserved during summer in split air-conditioned buildings.
•Occupants preferred slightly cool environment.•Acceptable temperature was 1.2 °C higher than that predicted by PPD.•8.6% of cooling energy could be saved during summer.•Adaptive comfort model can be applied in building split air-conditioned.
Ammonia (NH3) is typically present at higher concentrations in indoor air (∼10–70 ppb) than in outdoor air (∼50 ppt to 5 ppb). It is the dominant neutralizer of acidic species in indoor environments, ...strongly influencing the partitioning of gaseous acidic and basic species to aerosols, surface films, and bulk water. We have measured NH3 emissions from humans in an environmentally controlled chamber. A series of experiments, each with four volunteers, quantified NH3 emissions as a function of temperature (25.1–32.6 °C), clothing (long-sleeved shirts/pants or T-shirts/shorts), age (teenagers, adults, and seniors), relative humidity (low or high), and ozone (<2 ppb or ∼35 ppb). Higher temperature and more skin exposure (T-shirts/shorts) significantly increased emission rates. For adults and seniors (long clothing), NH3 emissions are estimated to be 0.4 mg h–1 person–1 at 25 °C, 0.8 mg h–1 person–1 at 27 °C, and 1.4 mg h–1 person–1 at 29 °C, based on the temperature relationship observed in this study. Human NH3 emissions are sufficient to neutralize the acidifying impacts of human CO2 emissions. Results from this study can be used to more accurately model indoor and inner-city outdoor NH3 concentrations and associated chemistry.
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•The research team examined the effects of indoor environmental variables on absence rates in elementary schools.•Higher classroom ventilation rates significantly reduced ...illness-related absences.•Higher concentrations of indoor long-term monitored PM2.5 were significantly associated with increased illness-related absences.•Although mechanically ventilated classrooms had relatively low indoor PM2.5, more rigorous control of indoor particles was still beneficial.
This study monitored indoor environmental data in 144 classrooms in 31 schools in the Midwestern United States for two consecutive days every fall, winter, and spring during a two-year period; 3,105 pupils attended classrooms where the measurements were conducted. All classrooms were ventilated with mechanical systems that had recirculation; there were no operable exterior windows or doors. The daily absence rate at the student level and demographic data at the classroom level were collected. The overall mean ventilation rate, using outdoor air, was 5.5 L/s per person (the corresponding mean carbon dioxide concentrations were < 2,000 ppm), and the mean indoor PM2.5 was 3.6 μg/m3. The annual illness-related absence rate at the classroom level was extracted from the student-level absence data and regressed on measured indoor environmental parameters. Significant associations were found. Every 1 L/s per person increase in ventilation rate was associated with a 5.59 decrease in days with absences per year. This corresponds to a 0.15% increase in the annual daily attendance rate. Every additional 1 μg/m3 of indoor PM2.5 was associated with a 7.37 increase in days with absences per year. This corresponds to a 0.19% decrease in the annual daily attendance rate. No other relationships were significant. Present results agree with the previously demonstrated benefits of reduced absence rates when classroom ventilation is improved and provide additional evidence on the potential benefits of reducing indoor inhalable particles. Overall, reduced absence rates are expected to provide socioeconomic benefits and benefits for academic achievements, while higher ventilation rates and reduced particle levels will also contribute to reduced health risks, including those related to airborne respiratory pathogens.
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