Ventilation and performance in office work

Building occupancy estimation using single channel CW radar and deep learning

Counting the number of people in a room is crucial for optimizing smart buildings, enhancing energy efficiency, and ensuring security while preserving privacy. This study introduces a novel radar-based occupancy estimation method leveraging a 24-GHz Continuous Wave (CW) radar system integrated with time-frequency mapping techniques using Continuous Wavelet Transform (CWT) and power spectrum analysis. Unlike previous studies that rely on WiFi or PIR-based sensors, this approach provides a robust alternative without privacy concerns. The time-frequency scalograms generated from radar echoes were used to train deep-learning models, including DarkNet19, MobileNetV2, and ResNet18. Experiments conducted with sedentary occupants over 4 hours and 40 minutes resulted in 1680 image samples. The proposed approach achieved high accuracy, with DarkNet19 performing the best, reaching 92.7% on CWT images and 92.3% on power spectrum images. Additionally, experiments in a walking environment with another continuous 1 hour of data achieved 86.5% accuracy, demonstrating the method's effectiveness beyond static scenarios. These results confirm that CW radar with deep learning can enable non-intrusive, privacy-preserving occupancy estimation for smart building applications.

Carbon dioxide guidelines for indoor air quality: a review

BACKGROUND

The importance of building ventilation to protect health has been more widely recognized since the COVID-19 pandemic. Outdoor air ventilation in buildings dilutes indoor-generated air pollutants (including bioaerosols) and reduces resulting occupant exposures. Many countries and organizations have advisory guidelines or mandatory standards for minimum ventilation rates (VRs) to maintain indoor air quality (IAQ). Because directly measuring VRs is often difficult, many IAQ guidelines instead specify indoor concentration limits for carbon dioxide (CO2), using CO2 exhaled by building occupants as an indicator of VR. Although indoor CO2 guidelines are common, the evidence basis for the various CO2 limits has not been clear.

OBJECTIVE

To review current indoor CO2 guidelines worldwide and the supportive evidence provided.

METHODS

We identified worldwide CO2-based guidelines for IAQ or ventilation, along with any supportive evidence provided. We excluded occupational guidelines for CO2 levels ≥5000 ppm.

RESULTS

Among 43 guidelines identified, 35 set single CO2 concentration limits and eight set multi-tiered limits; 16 mentioned no specific human effect to be controlled, 19 specified only odor dissatisfaction, five specified non-infectious health effects, and three specified airborne infectious disease transmission. The most common indoor CO2 limit was 1000 ppm. Thirteen guidelines specified maximum CO2 limits as extended time-weighted averages, none with evidence linking averaged limits to occupant effects. Of only 18 guidelines citing evidence to support limits set, we found this evidence persuasive for eight. Among these eight guidelines, seven set limits to control odor perception. One provided 17 scientifically-based CO2 limits, for specific example space uses and occupancies, to control long-range COVID-19 transmission indoors.

IMPACT

Many current indoor carbon dioxide (CO2) guidelines for indoor air quality specified no adverse effects intended for control. Odor dissatisfaction was the effect mentioned most frequently, few mentioned health, and three mentioned control of infectious disease. Only one CO2 guideline was developed from scientific models to control airborne transmission of COVID-19. Most guidelines provided no supportive evidence for specified limits; few provided persuasive evidence. No scientific basis is apparent for setting one CO2 limit for IAQ across all buildings, setting a CO2 limit for IAQ as an extended time-weighted average, or using any arbitrary one-time CO2 measurement to verify a desired VR.

Interactive effects of indoor environmental factors on work performance

Among a variety of environmental factors, operative temperature, relative humidity and ventilation rate are generally considered to be factors that significantly affect work performance, and the interactions among these three factors were quantitatively studied in this paper. Eighteen participants were recruited to complete the neurobehavioral ability tests in different environments by central composite design, and their performance was analysed by regression fitting and multi-factor coupling analysis. By defining the interval coefficient β, the interaction effects between the factors were calculated quantitatively. The results showed that: for the performance of perception and expression tasks, there was an antagonistic effect between operative temperature and relative humidity (β = 0.50 ∼ 0.82), between operative temperature and ventilation rate (β = -0.29 to -0.38), and among the three factors (β = 0.38-0.67). There was a synergy effect between relative humidity and ventilation rate (β = 1.71-2.28). For the performance of reasoning tasks, the interaction effect among the three factors and their combinations is antagonistic effect (β = 0.67-0.83).Practitioner summary: We proposed a method to calculate the quantitative relation of multi-factor interactions. In recent ergonomics studies, more and more factors have been included. This method can well describe the synergistic or antagonistic effect of the changes of other factors on the target factors.

Optimization of cabin seating arrangement strategies based on the Wells-Riley risk theory

Civil aviation transport is an important source of global respiratory disease spread due to the closely-spaced environment. In order to reduce the probability of infection of passengers, an improved Wells-Riley model for cabin passenger risk assessment have been given in this work, the cabin ventilation and passenger nose and mouth orientation were considered. The model's effectiveness has been verified with published data. Finally, how the load factor and use of an empty seat scheme are associated with the number of infected people was assessed. The results demonstrated that the number of infected people positively correlates with the passenger load factor, and the most suitable load factor can be determined by controlling the final number of infected people with the condition of the epidemic situation in the departure city. Additionally, infection risk was found to be lower among passengers in window seats than in those in aisle seats and middle seats, and keeping empty seats in the middle or aisle could reduce the cabin average probability of infection by up to 37.47%. Using the model developed here, airlines can determine the optimal load factor threshold and seating arrangement strategy to improve economic benefits and reduce the probability of passenger infection.

Simultaneous influence of light and CO2 on phytoremediation performance and physiological response of plants to formaldehyde

Phytoremediation technology is an effective method to remove formaldehyde indoors, but the purification capacity and physiological response of plants to formaldehyde under the simultaneous influence of light and CO₂ have not been examined in previous studies. In this study, formaldehyde fumigation experiments were conducted on the C₃ plants Epipremnum aureum A. and Chlorophytum comosum L., and the crassulacean acid metabolism (CAM) plant Dieffenbachia maculate A. The phytoremediation performance and physiological response of plants were studied. The initial concentration of formaldehyde was established at 11.950 ± 1.442 [Formula: see text]; the light intensities were 448 ± 7 [Formula: see text], 1628 ± 22 [Formula: see text], and 3259 ± 22 [Formula: see text], respectively; and the concentrations of CO₂ were 455 ± 29 [Formula: see text], 978 ± 50 [Formula: see text], 2020 ± 66 [Formula: see text], and 3006 ± 95 [Formula: see text], respectively. The results indicated that the highest purification rates of formaldehyde by E. aureum, D. maculata, and C. comosum were 55.8%, 43.7%, and 53.2%, respectively. The light intensity had a positive effect on the formaldehyde purification rates of all three plants and positively stimulated peroxidase (POD) activity, while the CO₂ concentration had no significant impact on the formaldehyde purification capacity and plants' physiological characteristics. Exposure to formaldehyde inhibited formaldehyde dehydrogenase (FADH) activity and positively stimulated catalase (CAT) activity. The superoxide dismutase (SOD) activity positively correlated with the formaldehyde purification capacity of plants.

Assessing the indoor air quality and their predictor variable in 21 home offices during the Covid-19 pandemic in Norway

In this study, concentrations of pollutants: formaldehyde, carbon dioxide (CO₂), and total volatile organic compounds (TVOC) and parameters: indoor room temperature and relative humidity (RH) were measured in 21 home offices for at least one week in winter in Trondheim, Norway. Eleven of these were measured again for the same duration in summer. Potentially explanatory variables of these parameters were collected, including building and renovation year, house type, building location, trickle vent status, occupancy, wood stove, floor material, pets, RH, and air temperature. The association between indoor air pollutants and their potential predictor variables was analyzed using generalized estimation equations to determine the significant parameters to control pollutants. Significantly seasonal differences in concentrations were observed for CO₂ and formaldehyde, while no significant seasonal difference was observed for TVOC. For TVOC and formaldehyde, trickle vent, RH, and air temperature were among the most important predictor variables. Although higher concentrations of CO₂ were measured in cases where the trickle vent was closed, the most important predictor variables for CO₂ were season, RH, and indoor air temperature. The formaldehyde concentrations were higher outside working hours but mostly below health thresholds recommendations; for CO₂, 11 of the measured cases had indoor concentrations exceeding 1000 ppm in 10% of the measured time. For TVOC, the concentrations were above the recommended values by WHO in 73% of the cases. RH was generally low in winter. The temperature was generally kept over the recommended level of 22-24 °C during working hours.

Pursuing occupants' health and well-being in building management: Definition of new metrics based on indoor air parameters

The spread of COVID-19 has affected the lives of millions of people. Pandemic has made people more sensitive to health issues. In particular, the growing concern for the virus spread in confined spaces has promoted the necessity to improve indoor air quality. Literature is stressing how buildings must be designed and operated pursuing occupants' health and well-being, with a particular attention for indoor air parameters. This poses the challenge of monitoring and assessing these aspects through proper metrics. In this paper the approach towards a multi-step assessment procedure embedding in buildings assessment health and well-being related variables and indicators is elaborated. They are intended to inform a building manager of the potential influence of air conditions on human health and well-being. Moreover, a set of monetary metrics (i.e., impacts) is proposed to translate energy and indoor air related building performances into euros, putting the basis for a comprehensive economic evaluation. The application of the set of proposed metrics to an Italian hotel (i.e., Italian pilot of H2020 MOBISTYLE project), enabled to map some indoor air conditions causing health concerns, and to identify clusters of guests with best and worst indoor air conditions, to be targeted by new management strategies. Despite case study specific limitations, the application exemplified how the methodology can expand the traditional energy-based performance assessment for building management towards indoor air domain and the related economic impacts, with implication on results in terms of overall economic performance of the building from both a private and public perspective.

Study on residential environment and workers' personality traits on productivity while working from home

Working from home has drawn more attention with the development of information and communications technology and the coronavirus disease 2019 pandemic. Although studies on working from home have been conducted in various academic fields, few have focused on residential environment and personality traits. In the present study, air temperature and humidity of the home workplace were measured and a questionnaire survey was conducted to understand the relationship between residential environment and personality traits and at-home work productivity. The results suggest that comprehensive productivity while working from home improved. However, when examining individual aspects of productivity, the productivity of information processing improved while that of knowledge processing and knowledge creation deteriorated. The results also suggest the importance of improving the residential environment when working from home because productivity while working from home rather than from the office improved with high evaluation of the residential environment. Moreover, productivity decreased for workers with high neuroticism and increased for those with high openness or perseverance and passion, suggesting that some personality traits are more or less suitable for working from home. To improve the productivity of all workers, these findings have practical implications for promoting appropriate maintenance of the residential environment and introducing flexible work styles that account for personality traits.

Effects of a cool classroom microclimate on cardiac autonomic control and cognitive performances in undergraduate students

An inverted U-shape relationship between cognitive performance and indoor temperature with best performance peaking at 21.6 °C was previously described. Little is known on classroom temperature reduction effects on cognitive performances and cardiac autonomic profile, during the cold season. Fifteen students underwent electrocardiogram recording during a lecture in two days in December when classroom temperatures were set as neutral (NEUTRAL, 20-22 °C) and cool (COOL, 16-18 °C). Cognitive performance (memory, verbal ability, reasoning, overall cognitive C-score) was assessed by Cambridge Brain Science cognitive evaluation tool. Cardiac autonomic control was evaluated via the analysis of spontaneous fluctuations of heart period, as the temporal distance between two successive R-wave peaks (RR). Spectral analysis provided the power in the high frequency (HF, 0.15-0.40 Hz) and low frequency (LF, 0.04-0.15 Hz) bands of RR variability. Sympatho-vagal interaction was assessed by LF to HF ratio (LF/HF). Symbolic analysis provided the fraction of RR patterns composed by three heart periods with no variation (0 V%) and two variations (2 V%), taken as markers of cardiac sympathetic and vagal modulations, respectively. The students' thermal comfort was assessed during NEUTRAL and COOL trials. Classroom temperatures were 21.5 ± 0.8 °C and 18.4 ± 0.4 °C during NEUTRAL and COOL. Memory, verbal ability, C-Score were greater during COOL (13.01 ± 3.43, 12.32 ± 2.58, 14.29 ± 2.90) compared to NEUTRAL (9.98 ± 2.26, p = 0.002; 8.57 ± 1.07, p = 0.001 and 10.35 ± 3.20, p = 0.001). LF/HF (2.4 ± 1.7) and 0 V% (23.2 ± 11.1%) were lower during COOL compared to NEUTRAL (3.7 ± 2.8, p = 0.042; 28.1 ± 12.2.1%, p = 0.031). During COOL, 2 V% was greater (30.5 ± 10.9%) compared to NEUTRAL (26.2 ± 11.3, p = 0.047). The students' thermal comfort was slightly reduced during COOL compared to NEUTRAL trial. During cold season, a better cognitive performance was obtained in a cooler indoor setting enabling therefore energy saving too.

Air Quality as a Key Factor in the Aromatisation of Stores: A Systematic Literature Review

Scientific literature on indoor air quality is categorised mainly into environmental sciences, construction building technology and environmental and civil engineering. Indoor air is a complex and dynamic mixture of a variety of volatile and particulate matter. Some of the constituents are odorous and originate from various sources, such as construction materials, furniture, cleaning products, goods in stores, humans and many more. The first part of the article summarises the knowledge about the substances that are found in the air inside buildings, especially stores, and have a negative impact on our health. This issue has been monitored for a long time, and so, using a better methodology, it is possible to identify even low concentrations of monitored substances. The second part summarises the possibility of using various aromatic substances to improve people’s sense of the air in stores. In recent times, air modification has come to the forefront of researchers’ interest in order to create a more pleasant environment and possibly increase sales.

Disproportionate exposure to urban heat island intensity across major US cities

Urban heat stress poses a major risk to public health. Case studies of individual cities suggest that heat exposure, like other environmental stressors, may be unequally distributed across income groups. There is little evidence, however, as to whether such disparities are pervasive. We combine surface urban heat island (SUHI) data, a proxy for isolating the urban contribution to additional heat exposure in built environments, with census tract-level demographic data to answer these questions for summer days, when heat exposure is likely to be at a maximum. We find that the average person of color lives in a census tract with higher SUHI intensity than non-Hispanic whites in all but 6 of the 175 largest urbanized areas in the continental United States. A similar pattern emerges for people living in households below the poverty line relative to those at more than two times the poverty line.

Impact of Cognitive Tasks on CO2 and Isoprene Emissions from Humans

The human body emits a wide range of chemicals, including CO₂ and isoprene. To examine the impact of cognitive tasks on human emission rates of CO₂ and isoprene, we conducted an across-subject, counterbalanced study in a controlled chamber involving 16 adults. The chamber replicated an office environment. In groups of four, participants engaged in 30 min each of cognitive tasks (stressed activity) and watching nature documentaries (relaxed activity). Measured biomarkers indicated higher stress levels were achieved during the stressed activity. Per-person CO₂ emission rates were greater for stressed than relaxed activity (30.3 ± 2.1 vs 27.0 ± 1.7 g/h/p, p = 0.0044, mean ± standard deviation). Isoprene emission rates were also elevated under stressed versus relaxed activity (154 ± 25 μg/h/p vs 116 ± 20 μg/h/p, p = 0.041). The chamber temperature was held constant at 26.2 ± 0.49 °C; incidental variation in temperature did not explain the variance in emission rates. Isoprene emission rates increased linearly with salivary α-amylase levels (r² = 0.6, p = 0.02). These results imply the possibility of considering cognitive tasks when determining building ventilation rates. They also present the possibility of monitoring indicators of cognitive tasks of occupants through measurement of air quality.

On the Optimal Indoor Air Conditions for SARS-CoV-2 Inactivation. An Enthalpy-Based Approach

In the CoViD-19 pandemic, the precautionary approach suggests that all possible measures should be established and implemented to avoid contagion, including through aerosols. For indoor spaces, the virulence of SARS-CoV-2 could be mitigated not only via air changes, but also by heating, ventilation, and air conditioning (HVAC) systems maintaining thermodynamic conditions possibly adverse to the virus. However, data available in literature on virus survival were never treated aiming to this. In fact, based on comparisons in terms of specific enthalpy, a domain of indoor comfort conditions between 50 and 60 kJ/kg is found to comply with this objective, and an easy-to-use relationship for setting viable pairs of humidity and temperature using a proper HVAC plant is proposed. If confirmed via further investigations on this research path, these findings could open interesting scenarios on the use of indoor spaces during the pandemic.

Assessment of Overheating Risk in Gynaecology Scanning Rooms during Near-Heatwave Conditions: A Case Study of the Royal Berkshire Hospital in the UK

Hospital buildings in the UK are at particular risk to rising summer temperatures associated with climate change. Balancing the thermal needs of patients, staff, and visitors is a challenging, complex endeavour. A case study of the ultrasound area of the Royal Berkshire Hospital's Maternity and Gynaecology building is presented, where temperatures were measured for 35 days in waiting areas, staff offices, and ultrasound scanning rooms, aiming to assess the overheating risk posed to occupants. Local external temperature measurements were used for comparison whereby determining the indoor-outdoor environmental connection. Results show that most rooms had already breached standard overheating thresholds within the study period. Anthropogenic and waste heat from equipment has a noticeable effect on indoor temperatures. Local air-conditioning helped reduce the peaks in temperature seen between 14:00 and 17:00 for similar scanning rooms but is in contradiction to the National Health Service's sustainability plans. Several low-level solutions such as improved signage, access to water, and the allocation of vulnerable patients to morning clinics are suggested. Barriers to solutions are also discussed and the requirement of sufficient maintenance plans for cooling equipment is empathised. These solutions are likely to be applicable to other hospital buildings experiencing similar conditions.

Differences in Occupants’ Satisfaction and Perceived Productivity in High- and Low-Performance Offices

This paper reports the results from a dataset comprising 9794 post-occupancy evaluation (POE) surveys from 77 Australian open-plan offices. This paper specifically focuses on a sub-set of 20 offices (n = 2133), identified from ranking 10 offices each, with the least (n = 1063) and highest (n = 1070) satisfaction scores, respectively. The satisfaction scores were evaluated on the basis of seven factors (i.e., building/office aesthetics and quality, thermal comfort and indoor air quality, noise distraction and privacy, personal control, connection to outdoor environment, maintenance and visual comfort, and individual space). Using the POE survey data from 20 offices, regression analyses and two-way ANOVA tests were carried out to understand the differences in occupants’ satisfaction and perceived productivity arising from open-plan offices. According to the statistically significant regression analyses results, it was identified that building/office aesthetics and quality (β = 0.55, p < 0.001) and noise distraction and privacy (β = 0.33, p < 0.001) were the two strongest predictors contributing perceived productivity in low-performance offices. Two-way ANOVA test results for the 10 high-performance offices indicate that the perceived productivity was strongly associated with the office’s physical configuration, the employees’ working experience, and the working hours at that office.

User-focused office renovation: a review into user satisfaction and the potential for improvement

Purpose

This paper highlights the importance of user satisfaction in office renovation. A user-focussed renovation approach can enhance user satisfaction in offices and their functional quality while meeting energy performance goals. The purpose of this paper is to investigate users’ needs and the physical and psychological factors affecting user satisfaction, as input to office renovation projects.

Design/methodology/approach

The selected articles are collected from Scopus, ScienceDirect and Google Scholar. Searching was limited to the main key terms of office, work environment, and user satisfaction and comfort. The important factors were searched through empirical-based international literature mainly. Based hereupon, a guide will be developed for the analysis and evaluation of user satisfaction in office renovations.

Findings

From a comprehensive overview, the findings present ten main factors to increase user satisfaction in office renovation. These are associated with physical and psychological satisfaction and comfort. In addition, the influential factors were categorised into three levels based on needs theories to organise the hierarchy of priorities.

Practical implications

This research adds to the body of knowledge about which factors are important for user satisfaction, based on what previous research has found in that field. This is important to improve the sustainability in use.

Originality/value

User satisfaction is often studied through separate aspects: health and indoor climate vs functionality and productivity. This paper examines overall user satisfaction of workplaces by integrating the perspectives of physical and psychological conditions, and by providing insight into the priority of satisfaction factors.

Indoor Sources of Air Pollutants

People spend an average of 90% of their time in indoor environments. There is a long list of indoor sources that can contribute to increased pollutant concentrations, some of them related to human activities (e.g. people's movement, cooking, cleaning, smoking), but also to surface chemistry reactions with human skin and building and furniture surfaces. The result of all these emissions is a heterogeneous cocktail of pollutants with varying degrees of toxicity, which makes indoor air quality a complex system. Good characterization of the sources that affect indoor air pollution levels is of major importance for quantifying (and reducing) the associated health risks. This chapter reviews some of the more significant indoor sources that can be found in the most common non-occupational indoor environments.

Impact of Low-Income Home Energy-Efficiency Retrofits on Building Air Tightness and Healthy Home Indicators

We studied 226 low-income households as a part of the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study to investigate the relationship between energy-efficiency retrofits (EERs) specific to air sealing of residential building envelopes, annual average infiltration rates (AAIR), and qualitative indicators of “healthy” homes. Blower door tests quantified the leakage area in each home, which was used to estimate the AAIR. Walk-through inspections were used to record observations of air-sealing retrofits conducted as part of Colorado’s Weatherization Assistance Program and indirect indicators of poor indoor environmental quality (IEQ) in the homes, such as visible mold or stains, visible dust on hard surfaces, vapor condensation on windows, dampness, and perceived air quality. Results showed that building characteristics like age and volume affected AAIR more significantly than air-sealing EERs. Among the air-sealing EERs, homes with the air-handler ductwork sealed and windows weather-stripped were found to have significantly lower AAIR compared to the homes without these features. Mold growth, wall stains, notably higher levels of dust, and unacceptable odor levels were more frequently reported in homes with higher AAIR, showing that leakier homes do not necessarily have better IEQ.

Sick Building Syndrome and Other Building-Related Illnesses

Sick building syndrome (SBS) and building-related illnesses are omnipresent in modern high-rise buildings. The SBS is a complex spectrum of ill health symptoms, such as mucous membrane irritation, asthma, neurotoxic effects, gastrointestinal disturbance, skin dryness, sensitivity to odours that may appear among occupants in office and public buildings, schools and hospitals. Studies on large office buildings from USA, UK, Sweden, Finland, Japan, Germany, Canada, China, India, Netherlands, Malaysia, Taiwan, and Thailand, substantiate the occurrence of SBS phenomena. The accumulated effects of a multitude of factors, such as the indoor environmental quality, building characteristics, building dampness, and activities of occupants attribute to SBS. A building occupant manifests at least one symptom of SBS, the onset of two or more symptoms at least twice, and rapid resolution of symptoms following moving away from the workstation or building may be defined as having SBS. Based on the peer-reviewed documentation, this chapter elaborates the magnitude of building-related health consequences due to measurable environmental causations, and the size of the population affected. The mechanisms and causative factors of SBS and illnesses include, for example, the oxidative stress resulting from indoor pollutants, VOCs, office work-related stressors, humidification, odours associated with moisture and bioaerosol exposure. Related regulatory standards and strategies for management of SBS and other illnesses are elaborated.

Have a look around: the effect of physical environments on risk behaviour in work-related versus non-work related decision-making tasks

Due to ubiquitous computing, knowledge workers do not only work in typical work-associated environments (e.g. the office) but also wherever it best suits their schedule or preferences (e.g. the park). In two experiments using laboratory and field methods, we compared decision making in work and non-work environments. We hypothesised that participants make riskier work-related decisions when in work-associated environments and riskier non-work-related decisions in non-work-associated environments. Therefore, if environment (work vs. non-work) and decision-making task (work-related vs. non-work-related) are incongruent, then risk-taking should be lower, as the decision maker might feel the situation is unusual or inappropriate. Although results do not reveal that work-associated environments generally encourage riskier work-related decisions (and likewise for non-work), we found environmental effects on decision making when including mood as a moderator. Practitioner summary: Mobile workers are required to make decisions in various environments. We assumed that decisions are more risky when they are made in a fitting environment (e.g. work-related decisions in work environments). Results of the two experiments (laboratory and field) only show an environmental effect when mood is included as a moderator.

Towards practical indoor air phytoremediation: A review

Indoor air quality has become a growing concern due to the increasing proportion of time people spend indoors, combined with reduced building ventilation rates resulting from an increasing awareness of building energy use. It has been well established that potted-plants can help to phytoremediate a diverse range of indoor air pollutants. In particular, a substantial body of literature has demonstrated the ability of the potted-plant system to remove volatile organic compounds (VOCs) from indoor air. These findings have largely originated from laboratory scale chamber experiments, with several studies drawing different conclusions regarding the primary VOC removal mechanism, and removal efficiencies. Advancements in indoor air phytoremediation technology, notably active botanical biofilters, can more effectively reduce the concentrations of multiple indoor air pollutants through the action of active airflow through a plant growing medium, along with vertically aligned plants which achieve a high leaf area density per unit of floor space. Despite variable system designs, systems available have clear potential to assist or replace existing mechanical ventilation systems for indoor air pollutant removal. Further research is needed to develop, test and confirm their effectiveness and safety before they can be functionally integrated in the broader built environment. The current article reviews the current state of active air phytoremediation technology, discusses the available botanical biofiltration systems, and identifies areas in need of development.

How home ventilation rates affect health: A literature review

This paper reviews studies of the relationships between ventilation rates (VRs) in homes and occupant health, primarily respiratory health. Five cross-sectional studies, seven case-control studies, and eight intervention studies met inclusion criteria. Nearly all studies controlled for a range of potential confounders and most intervention studies included placebo conditions. Just over half of studies reported one or more statistically significant (SS) health benefits of increased VRs. Wheeze was most clearly associated with VR. No health outcomes had SS associations with VRs in the majority of statistical tests. Most studies that reported SS health benefits from increased VRs also had additional health outcomes that did not improve with increased VRs. Overall, the number of SS improvements in health with increased VRs exceeded the anticipated chance improvements by approximately a factor of seven. The magnitude of the improvements in health outcomes with increased VRs ranged from 20% to several-fold improvements. In summary, the available research indicates a tendency for improvements in respiratory health with increased home VRs; however, health benefits do not occur consistently and other exposure control measures should be used together with ventilation. The research did not enable identification of a threshold VR below which adverse health effects occur.

Outcome-based ventilation: A framework for assessing performance, health, and energy impacts to inform office building ventilation decisions

This article presents an outcome-based ventilation (OBV) framework, which combines competing ventilation impacts into a monetized loss function ($/occ/h) used to inform ventilation rate decisions. The OBV framework, developed for U.S. offices, considers six outcomes of increasing ventilation: profitable outcomes realized from improvements in occupant work performance and sick leave absenteeism; health outcomes from occupant exposure to outdoor fine particles and ozone; and energy outcomes from electricity and natural gas usage. We used the literature to set low, medium, and high reference values for OBV loss function parameters, and evaluated the framework and outcome-based ventilation rates using a simulated U.S. office stock dataset and a case study in New York City. With parameters for all outcomes set at medium values derived from literature-based central estimates, higher ventilation rates' profitable benefits dominated negative health and energy impacts, and the OBV framework suggested ventilation should be ≥45 L/s/occ, much higher than the baseline ~8.5 L/s/occ rate prescribed by ASHRAE 62.1. Only when combining very low parameter estimates for profitable impacts with very high ones for health and energy impacts were all outcomes on the same order. Even then, however, outcome-based ventilation rates were often twice the baseline rate or more.

The effect of low ventilation rate with elevated bioeffluent concentration on work performance, perceived indoor air quality, and health symptoms

The aim of this laboratory experiment was to study the effects of ventilation rate, and related changes in air quality, predominantly bioeffluents, on work performance, perceived indoor air quality, and health symptoms in a typical conditions of modern open-plan office with low material and equipment emissions. In Condition A, outdoor air flow rate of 28.2 l/s person (CO₂ level 540 ppm) was applied and in Condition B, outdoor air flow rate was 2.3 l/s person (CO₂ level 2260 ppm). CO₂ concentration level was used as an indicator of bioeffluents. Performance was measured with seven different tasks which measure different cognitive processes. Thirty-six subjects participated in the experiment. The exposure time was 4 hours. Condition B had a weak negative effect on performance only in the information retrieval tasks. Condition B increased slightly subjective workload and perceived fatigue. No effects on health symptoms were found. The intensity of symptoms was low in both conditions. The experimental condition had an effect on perceived air quality and observed odor intensity only in the beginning of the session. Although the room temperature was controlled in both conditions, the heat was perceived to impair the performance more in Condition B.

Do classroom ventilation rates in California elementary schools influence standardized test scores? Results from a prospective study

Limited evidence has associated lower ventilation rates (VRs) in schools with reduced student learning or achievement. We analyzed longitudinal data collected over two school years from 150 classrooms in 28 schools within three California school districts. We estimated daily classroom VRs from real-time indoor carbon dioxide measured by web-connected sensors. School districts provided individual-level scores on standard tests in Math and English, and classroom-level demographic data. Analyses assessing learning effects used two VR metrics: average VRs for 30 days prior to tests, and proportion of prior daily VRs above specified thresholds during the year. We estimated relationships between scores and VR metrics in multivariate models with generalized estimating equations. All school districts had median school-year VRs below the California VR standard. Most models showed some positive associations of VRs with test scores; however, estimates varied in magnitude and few 95% confidence intervals excluded the null. Combined-district models estimated statistically significant increases of 0.6 points (P = 0.01) on English tests for each 10% increase in prior 30-day VRs. Estimated increases in Math were of similar magnitude but not statistically significant. Findings suggest potential small positive associations between classroom VRs and learning.

The effect of increased classroom ventilation rate indicated by reduced CO2 concentration on the performance of schoolwork by children

The article reports on an experiment which investigated the effect of increased classroom ventilation rate on the performance of children aged 10-12 years. The experiment was executed at two different schools (two classrooms at each school) as a double-blind 2 × 2 crossover intervention where four different performance tests were used as surrogates for short-term concentration and logical thinking. Only complete pairs of test responses were included in the within-subject comparisons of performance, and data were not corrected for learning and fatigue effects. Analysis of the total sample suggested the number of correct answers was improved significantly in four of four performance test, addition (6.3%), number comparison (4.8%), grammatical reasoning (3.2%), and reading and comprehension (7.4%), when the outdoor air supply rate was increased from an average of 1.7 (1.4-2.0) to 6.6 l/s per person. The increased outdoor air supply rate did not have any significant effect on the number of errors in any of the performance tests. Results from questionnaires regarding pupil perception of the indoor environment, reported Sick Building Syndrome symptoms, and motivation suggested that the study classroom air was perceived more still and pupil were experiencing less pain in the eyes in the recirculation condition compared to the fresh air condition.

The effect of slightly warm temperature on work performance and comfort in open-plan offices - a laboratory study

The aim of the study was to determine the effect of a temperature of 29°C on performance in tasks involving different cognitive demands and to assess the effect on perceived performance, subjective workload, thermal comfort, perceived working conditions, cognitive fatigue, and somatic symptoms in a laboratory with realistic office environment. A comparison was made with a temperature of 23°C. Performance was measured on the basis of six different tasks that reflect different stages of cognitive performance. Thirty-three students participated in the experiment. The exposure time was 3.5 h in both thermal conditions. Performance was negatively affected by slightly warm temperature in the N-back working memory task. Temperature had no effect on performance in other tasks focusing on psychomotor, working memory, attention, or long-term memory capabilities. Temperature had no effect on perceived performance. However, slightly warm temperature caused concentration difficulties. Throat symptoms were found to increase over time at 29°C, but no temporal change was seen at 23°C. No effect of temperature on other symptoms was found. As expected, the differences in thermal comfort were significant. Women perceived a temperature of 23°C colder than men.

Perceptions in the U.S. building industry of the benefits and costs of improving indoor air quality

How building stakeholders (e.g. owners, tenants, operators, and designers) understand impacts of Indoor Air Quality (IAQ) and associated energy costs is unknown. We surveyed 112 stakeholders across the United States to ascertain their perceptions of their current IAQ and estimates of benefits and costs of, as well as willingness to pay for, IAQ improvements. Respondents' perceived IAQ scores correlated with the use of high-efficiency filters but not with any other IAQ-improving technologies. We elicited their estimates of the impacts of a ventilation-filtration upgrade (VFU), that is, doubling the ventilation rate from 20 to 40 cfm/person (9.5 to 19 l/s/person) and upgrading from a minimum efficiency reporting value 6 to 11 filter, and compared responses to estimates derived from IAQ literature and energy modeling. Minorities of respondents thought the VFU would positively impact productivity (45%), absenteeism (23%), or health (39%). Respondents' annual VFU cost estimates (mean = $257, s.d. = $496, median = $75 per person) were much higher than ours (always <$32 per person), and the only yearly cost a plurality of respondents said they would pay for the VFU was $15 per person. Respondents holding green building credentials were not more likely to affirm the IAQ benefits of the VFU and were less likely to be willing to pay for it.

Effects of ventilation rate per person and per floor area on perceived air quality, sick building syndrome symptoms, and decision-making

Ventilation rates (VRs) in buildings must adequately control indoor levels of pollutants; however, VRs are constrained by the energy costs. Experiments in a simulated office assessed the effects of VR per occupant on perceived air quality (PAQ), Sick Building Syndrome (SBS) symptoms, and decision-making performance. A parallel set of experiments assessed the effects of VR per unit floor area on the same outcomes. Sixteen blinded healthy young adult subjects participated in each study. Each exposure lasted four hours and each subject experienced two conditions in a within-subject study design. The order of presentation of test conditions, day of testing, and gender were balanced. Temperature, relative humidity, VRs, and concentrations of pollutants were monitored. Online surveys assessed PAQ and SBS symptoms and a validated computer-based tool measured decision-making performance. Neither changing the VR per person nor changing the VR per floor area, had consistent statistically significant effects on PAQ or SBS symptoms. However, reductions in either occupant-based VR or floor-area-based VR had a significant and independent negative impact on most decision-making measures. These results indicate that the changes in VR employed in the study influence performance of healthy young adults even when PAQ and SBS symptoms are unaffected.

PRACTICAL IMPLICATIONS

The study results indicate the importance of avoiding low VRs per person and low VRs per floor area to minimize decrements in cognitive performance.

Breaking the circle of blame for sustainable buildings – evidence from Nordic countries

Purpose

– The study aims to examine how the vicious circle of blame for sustainable buildings can be turned into virtuous loops of adaptation when considering sustainable buildings and what are the drivers for tenants and investors regarding sustainable buildings and gaining insights of investors’ and tenants’ corporate responsibility (CR) actions.

Design/methodology/approach

– The paper consists of a literature review and two surveys. The literature review concentrates on exploring investors’ and tenants’ CR and sustainability drivers. Empirical evidence was gathered via two specific surveys. The first survey targeted investors, and the second survey targeted tenants to determine the focus areas of sustainability.

Findings

– The findings of this study indicate that the vicious circle of blame can be turned into one of cooperation with respect to sustainable buildings if the mutual drivers for improving sustainability are linked with investor–tenant collaboration. Based on the survey, the tenants claim that productivity, corporate culture and image are the primary drivers for sustainable buildings, whereas the investors claim that corporate culture and image, tenant demand and marketability are the primary drivers. Both parties mentioned the same sustainability drivers: corporate culture and image and lower operating costs. However, it was found that investors are not communicating their CR actions to public or promoting image and productivity benefits of green buildings to potential tenants.

Research limitations/implications

– The limitation of this study is the sampling of Nordic countries, as there are indications of different situation in other markets such as the USA.

Originality/value

– Improving sustainability in the real estate industry is linked to investor–tenant collaboration. In addition to common drivers, both investors and tenants have their own list of benefits and drivers for sustainable buildings. These drivers are linked to each other. Making progress with respect to sustainability in the built environment depends on people in the industry being aware of the importance of and possibilities offered by sustainable buildings, as well as being able and willing to act on this knowledge. Only through partnership can the full potential of the built environment be realised and help deliver an economically, environmentally and socially sustainable future.

Energy and cost associated with ventilating office buildings in a tropical climate

Providing sufficient amounts of outdoor air to occupants is a critical building function for supporting occupant health, well-being and productivity. In tropical climates, high ventilation rates require substantial amounts of energy to cool and dehumidify supply air. This study evaluates the energy consumption and associated cost for thermally conditioning outdoor air provided for building ventilation in tropical climates, considering Singapore as an example locale. We investigated the influence on energy consumption and cost of the following factors: outdoor air temperature and humidity, ventilation rate (L/s per person), indoor air temperature and humidity, air conditioning system coefficient of performance (COP), and cost of electricity. Results show that dehumidification of outdoor air accounts for more than 80% of the energy needed for building ventilation in Singapore's tropical climate. Improved system performance and/or a small increase in the indoor temperature set point would permit relatively large ventilation rates (such as 25 L/s per person) at modest or no cost increment. Overall, even in a thermally demanding tropical climate, the energy cost associated with increasing ventilation rate up to 25 L/s per person is less than 1% of the wages of an office worker in an advanced economy like Singapore's. This result implies that the benefits of increasing outdoor air ventilation rate up to 25 L/s per person--which is suggested to provide for productivity increases, lower sick building syndrome symptom prevalence, and reduced sick leave--can be much larger than the incremental cost of ventilation.

Challenges in Developing Ventilation and Indoor Air Quality Standards: The Story of ASHRAE Standard 62

Building ventilation has long been recognized for its role in occupant health, comfort and productivity, with some of the first recommendations on building ventilation rates published in the 19^th century. These recommendations were subsequently transformed into more rigorous standards and guidance in the 20^th century, with the first version of ASHRAE Standard 62 published in 1973. Since that time, ventilation standards have been issued in several countries around the world and have dealt with an increasingly complex and challenging range of issues as research on indoor air quality and the state of knowledge of building performance have progressed. This paper reviews and discusses some of the issues that have been addressed in the development of ventilation standards in recent years using the development of ASHRAE Standard 62 as context, including: the scientific bases for ventilation requirements, perceived indoor air quality, contaminant sources from occupants and the building, outdoor air quality, airborne contaminant limits, indoor carbon dioxide concentrations, environmental tobacco smoke, and performance-based design. Issues that are expected to be dealt with as Standard 62 and other standards are developed into the future are also reviewed.

CO2 generation rate in Chinese people

Carbon dioxide (CO2 ) metabolically produced by humans has been widely used as a tracer gas for determining ventilation rates in occupied rooms. Among other necessities, the method requires good estimates of human CO2 generation rates. An empirically derived equation is widely used to calculate the CO2 generation rate. However, there are indications that this equation is not valid for young Chinese people. In this study, we measured the CO2 generation rate of 44 young Chinese people at two typical activity levels, quiet sitting and relaxed standing. We found that the commonly used empirical equation overpredicted CO2 generation rates, but could be corrected with a factor of 0.75 for Chinese females and of 0.85 for Chinese males. The variance for measured CO2 sitting was much smaller than for standing, and hence, we concluded that sitting yields more precise CO2 generation estimates. The relative contributions of sex, height, weight, and metabolic rate were analyzed. We concluded that the error in estimating metabolic rate is responsible for most of the difference in measured generation of CO2 from the empirical equation's predictions.

PRACTICAL IMPLICATIONS

The tracer gas method using CO2 generated by people is widely used to calculate ventilation rate. However, the empirically derived equation that is normally used to estimate CO2 generation rate is not suitable for young Chinese people at rest. To estimate the CO2 generation rate in Chinese people under low-activity conditions, the empirical equation should be multiplied by correction factors of 0.75 and 0.85 for females and males, respectively.

Office workers' sick building syndrome and indoor carbon dioxide concentrations

This study attempted to determine whether any association exists between sick building syndrome (SBS) and indoor carbon dioxide (CO(2)) concentrations. We evaluated SBS among 111 office workers in August and November 2003. The environmental conditions in the office, including CO(2) concentrations, temperature, relative humidity, and fine particulate matter (PM(2.5)), were continuously monitored. The most prevalent symptoms of the five SBS groups were eye irritation and nonspecific and upper respiratory symptoms. The generalized estimating equation (GEE) models show that workers exposed to indoor CO(2) levels greater than 800 ppm were likely to report more eye irritation or upper respiratory symptoms.

Benefits and costs of improved IEQ in U.S. offices

This study estimates some of the benefits and costs of implementing scenarios that improve indoor environmental quality (IEQ) in the stock of U.S. office buildings. The scenarios include increasing ventilation rates when they are below 10 or 15 l/s per person, adding outdoor air economizers and controls when absent, eliminating winter indoor temperatures >23°C, and reducing dampness and mold problems. The estimated benefits of the scenarios analyzed are substantial in magnitude, including increased work performance, reduced Sick Building Syndrome symptoms, reduced absence, and improved thermal comfort for millions of office workers. The combined potential annual economic benefit of a set of nonoverlapping scenarios is approximately $20 billion. While the quantitative estimates have a high uncertainty, the opportunity for substantial benefits is clear. Some IEQ improvement measures will save energy while improving health or productivity, and implementing these measures should be the highest priority.

PRACTICAL IMPLICATIONS

Owners, designers, and operators of office buildings have an opportunity to improve IEQ, health, work performance, and comfort of building occupants and to obtain economic benefits by improving IEQ. These benefits can be achieved with simultaneous energy savings or with only small increases in energy costs.

The effects of outdoor air supply rate on work performance during 8-h work period

The purpose of this study is to evaluate the effect of ventilation rate on work performance and perceived air quality through short-term laboratory experiments. The experiment was designed to simulate office work, and a laboratory space was modified using new finish materials to become a typical office space. High levels of volatile organic compounds (VOCs) were found in the exposure chamber, most probably originating from the new finishing materials that were present. Twenty-four subjects were divided into six groups that were randomly exposed to the three ventilation rates, 5, 10, and 20 l/s per person. The subjects performed work tasks three separate times for each ventilation rate over an 8-h exposure period. The work performance of the subjects logarithmically improved with increased ventilation rates, which was similar to the previous research findings. Statistical significance was found for addition task, text-typing task, and memorization task. Increased work performance in this experiment was slightly lower than the results of previous short-term laboratory experiments, yet remained higher than results of previous long-term field experiments. However, it was difficult to directly compare the results of this experiment with those of previous experiments, because of the higher concentration of VOC present in the office rooms and the learning effect associated with the repeated tasks.

PRACTICAL IMPLICATIONS

The results of this experiment show that ventilation had positive impacts on perceived air quality and work performance for the subjects tested. Work performance logarithmically increased by approximately 2.5-5% as ventilation rates were increased from 5 to 20 l/s per person. The positive effect of ventilation rate on work performance was shown to be limited at the low ventilation rate. The positive effects on work performance were at lower ventilation rates. The learning effect in repeated work performance tasks could increase the uncertainty of the work performance analysis in 8-h exposure period.

Association between substandard classroom ventilation rates and students' academic achievement

This study focuses on the relationship between classroom ventilation rates and academic achievement. One hundred elementary schools of two school districts in the southwest United States were included in the study. Ventilation rates were estimated from fifth-grade classrooms (one per school) using CO(2) concentrations measured during occupied school days. In addition, standardized test scores and background data related to students in the classrooms studied were obtained from the districts. Of 100 classrooms, 87 had ventilation rates below recommended guidelines based on ASHRAE Standard 62 as of 2004. There is a linear association between classroom ventilation rates and students' academic achievement within the range of 0.9-7.1 l/s per person. For every unit (1 l/s per person) increase in the ventilation rate within that range, the proportion of students passing standardized test (i.e., scoring satisfactory or above) is expected to increase by 2.9% (95%CI 0.9-4.8%) for math and 2.7% (0.5-4.9%) for reading. The linear relationship observed may level off or change direction with higher ventilation rates, but given the limited number of observations, we were unable to test this hypothesis. A larger sample size is needed for estimating the effect of classroom ventilation rates higher than 7.1 l/s per person on academic achievement.

PRACTICAL IMPLICATIONS

The results of this study suggest that increasing the ventilation rates toward recommended guideline ventilation rates in classrooms should translate into improved academic achievement of students. More studies are needed to fully understand the relationships between ventilation rate, other indoor environmental quality parameters, and their effects on students' health and achievement. Achieving the recommended guidelines and pursuing better understanding of the underlying relationships would ultimately support both sustainable and productive school environments for students and personnel.

Airborne bacteria concentrations and related factors at university laboratories, hospital diagnostic laboratories and a biowaste site

Aims

To evaluate concentrations of airborne bacteria in university laboratories, hospital diagnostic laboratories, and a biowaste site in Seoul, Korea. To measure total airborne bacteria (TAB), the authors assessed sampling site, type of ventilation system, weather and detection of Gram-negative bacteria (GNB), indoors and outdoors.

Method

An Andersen one-stage sampler (Quick Take 30; SKC Inc) was used to sample air at a flow rate of 28.3 l/min for 5 min on nutrient medium in Petri dishes located on the impactor. A total of 236 samples (TAB, 109 indoor and nine outdoor; GNB, 109 indoor and nine outdoor) were collected three times in each spot from the 11 facilities to compare airborne bacteria concentrations.

Results

TAB concentrations ranged from undetectable to 3451 CFU/m3 (mean 384 CFU/m3), and GNB concentrations from undetectable to 394 CFU/m3 (mean 17 CFU/m3). TAB concentrations were high in window-ventilated facilities and facilities in which GNB were detected; concentrations were also high when it was rainy (all p values <0.05). TAB concentrations correlated significantly with GNB (r=0.548, p<0.01), number of bacteria species (r=0.351, p<0.01) and temperature (r=0.297, p<0.01). The presence of heating, ventilating, and air conditioning (HVAC), the number of TAB species and the detection of GNB affect TAB concentrations in laboratories.

Conclusions

It is recommended that special attention be given to regular control of indoor environments to improve the air quality of university and hospital laboratories.