Research has shown that even though the indoor environmental conditions seem to comply with current standards and guidelines and those conditions seem ‘comfortable’ enough, staying indoors is not good for our health. Reasons for this discrepancy might be the fact that these guidelines (such as ventilation rate, lighting level, and temperature ranges) are mainly based on single-dose response relationships (effect modelling using dose-related indicators) for the physical stressors (e.g. odour, light, sound, and temperature) determined for an average adult person. They are aimed at preventing short-term discomfort rather than long-term negative health effects, ignoring situation-related aspects and different preferences and needs of occupants. A more comprehensive model, accounting for integrated effects of all stressors, and different preferences and needs of occupants in different scenarios and situations, based on situation modelling making use of building and occupant-related indicators, is introduced and partly validated in a series of field studies in different scenarios. Based on the outcome of these field studies and insights from other studies, the methods, indicators and in particular the human model are discussed. Research directions to go beyond the mainly comfort-based dose-related indicators in our IEQ (indoor environmental quality)-guidelines are proposed.

During perception with our senses, interactions of different environmental stressors at brain level might occur. Previous studies have shown cross-modal effects between sound and odour. To test these effects of different sounds and levels of sounds on the perception of sound, temperature, odour, and light, as well as a number of physiological indicators, sixteen students were exposed to four different sounds (two indoor: mechanical ventilation & people talking; two outdoor: quiet rural area & city centre area) and two different sound pressure levels per sound, while sitting in a semi-lab environment. Bodily responses were sampled with wearable devices. Heart rate and breathing rate were monitored using a smart watch; EEG measurements were performed to assess their attention and mental relaxation levels; Acceptability and experience were assessed through a questionnaire to assess their comfort perception. Additionally, each student took a hearing test. The outcome showed when the traffic sound level increased, the students perceived the air as more smelly and less acceptable. The other sounds did not show any cross-modal effect. Moreover, heart rate and breathing rate significantly differed during the different tests, confirming that these two indicators can help to explain the physiological effect of noise as a stressor.

De via de lucht overgedragen infectieuze respiratoire deeltjes (IRDs), ook wel aerosolen genoemd, zijn de primaire route van overdracht voor respiratoire infectieuze ziektes zoals COVID-19 [1]. Klaslokalen hebben een verhoogd risico op besmetting vanwege de lange en hoge bezetting [2]. Deze overdracht kan dichtbij plaatsvinden, maar ook verder weg. Tijdens een door ZonMw gefinancierd veldonderzoek naar de verspreiding van het SARS-CoV-2 virus en de binnenmilieucondities in klaslokalen [3], bleek zowel de ventilatie als de temperatuur onvoldoende te zijn. Scholen hebben behoefte aan beheersbare maar ook betaalbare oplossingen. Mobiele luchtreinigers (MLRs) zijn een mogelijke (betaalbare) oplossing om overdracht van IRDs op lange afstand te verminderen. In opdracht van het Ministerie van Onderwijs Cultuur en Wetenschap werd daarom een vervolgonderzoek gestart met de vraag: zouden mobiele luchtreinigers in een toekomstige pandemie de situatie kunnen verbeteren?

University students spend a considerable time at study places. The acoustical quality of these study places is one of the indoor environmental qualities (IEQ) that can have an impact on student’s health, comfort, and performance. The indoor soundscape approach has been introduced to better understand occupants’ sound perception and experience of sounds in relation to the environment. This study aims to explore the indoor soundscapes of home study places of these students by conducting semi-structured interviews with 23 university students with different profiles. For qualitative analysis, open coding was used. Sub-categories, based on the codes, and categories were created and assigned to the soundscape themes that are defined in ISO 12913-1. An affinity diagram consisting of the themes, categories, and sub-categories was initially developed. Then, it was validated through two workshops with participants. The results showed that the interpretation of the sound environment, responses, and outcomes differed among the students. In a previous study, 451 students were clustered in 5 clusters with similar acoustical preferences (profiles). Therefore, it is recommended to consider making the indoor soundscape approach applicable for different profiles of occupants.

Understanding students' preferences of their study place, in particular acoustical and psychosocial preferences, is important to students' health and comfort. This study aimed to identify clusters of students with similar acoustical and psychosocial preferences, and to identify reasons for certain preferences of students in each cluster. A mixed-methods approach was applied, consisting of a questionnaire, which was completed by 451 bachelor students, and a field study conducted with 23 students from the same sample. The questionnaire data included among others acoustical and psychosocial preferences scores, while the field study data comprised interview transcripts, building checklists, and sound pressure level measurements. The questionnaire data were analysed using TwoStep cluster analysis to identify clusters of students based on their acoustical and psychosocial preferences. This produced five clusters of students that significantly differed in 14 variables, including preferences and perception of indoor environmental quality (e.g., noise from outside). Then, the field study data were analysed and categorised based on the five clusters of the students. The outcome explained the aspects associated with the acoustical preferences of students in each cluster. Building-related indicators such as the location of the building were found as an aspect that could affect the student's acoustical preferences. This study provides insight into the profiles of students based on their acoustical and psychosocial preferences, which are important for their health and comfort at their study places.

Previous studies have shown that sound influences students both physiologically and perceptually. However, most of these studies focussed on the effects of sounds at group-level, ignoring individual differences. Therefore, we investigated which indicators can be used to identify differences in bodily responses and perceptual assessments of each individual when exposed to four different sounds. First, based on an audiometric test, the hearing acuity of 15 students (from five different profiles based on their acoustical preferences and needs) was measured. Then, two sound exposure experiments were conducted in the SenseLab: direct sound exposure using earbuds in a laboratory setting, and indirect sound exposure with speakers in a real room setting. During each experiment, the attention level (AL), mental relaxation level (MRL), heart rate (HR), and respiration rate (RR) were measured with wearable devices, and students made perceptual assessments of each condition. The percentage of change normalised the four bodily response measurements among students. Based on correlation analysis and t-tests, bodily responses, and perceptual assessments across experiments were compared, at group-level and individual-level. Six students, who suffered from mild hearing loss in low-frequency sounds, showed bodily responses such as increased HR during exposure to low-frequency sound conditions. Perceptual assessments of different sound types during both lab experiments substantiated the acoustical preferences of the students from the five profiles. Bodily responses showed no strong nor significant correlations with perceptual assessments during the direct sound exposure experiments. Differences in bodily responses and perceptual assessments between the two experiments and between group-level and individual-level were observed in AL. It is concluded that hearing acuity and type of sound (sound frequencies) are key indicators for identifying differences in bodily responses (such as HR and RR) and perceptual assessment. For future research, it is crucial to consider incorporating audiometric tests, bodily responses such as HR and RR, and perceptual assessments in this type of investigations.

Changing outdoor conditions, i.e. higher outdoor air temperature, higher occurrence of heatwaves and outdoor air pollution, increase the risk of overheating and accumulation of air pollution in homes. Previous studies showed that high indoor air temperatures and air pollution affect occupants’ health, resulting in cardio-vascular and respiratory diseases, eyes and skin symptoms, and mortality. Measures to increase energy efficiency of renovated and newly built homes can further increase health risks during extreme weather events and can increase the outdoor temperature. Moreover, the rise of the outdoor air temperature in Europe is higher than the global average.

Therefore, understanding of the extent of current overheating and indoor air pollution and of the contributing factors is necessary to identify the required adaptability of dwellings in Europe to changing outdoor conditions. The objective of this study is to systematically review consequences of changing outdoor conditions, building characteristics, and technology on the indoor environment and occupants’ health in homes in European countries during summer.

This review focuses on empirical studies, as these enable to capture real world interactions of occupants and buildings in relation to outdoor conditions. Varying outdoor conditions, building-, and occupant-related aspects in different European climate zones are discussed. Main findings are that overheating already occurs in normal summers in temperate and northern European countries, while variation in overheating is related to occupants’ adaptative behaviour and building-related aspects. Based on the review, it is suggested to investigate adaptability of dwellings to changing occupants’ needs, new energy efficient technologies, and changing outdoor conditions.

As mandatory masking and social distancing measures decrease post-COVID-19, the risk of airborne pathogen transmission in crowded indoor spaces remains a significant public health concern. The pandemic highlighted the critical role of indoor air quality and ventilation in mitigating the spread of infectious diseases, underscoring the urgent need to improve our understanding and prediction of indoor airflow to minimise airborne transmission. In this review, studies on airborne transmission in indoor settings were systematically reviewed to identify research gaps and recommend changes in approach. The analysis is categorised into indoor airflow, dynamics of infectious respiratory particles (IRPs), and investigation methodologies. Findings reveal that almost 40% of the reviewed literature does not specify the type of indoor setting, with only 3% focusing on restaurant environments. Additionally, indoor air conditions are typically assumed to be constant, and respiratory activities are often limited to coughing and breathing. The review identifies the challenge of replicating the complex behaviour of IRPs in experiments and the computational expense of predicting turbulent indoor flows. Recommendations for future research include: i) focusing on social settings like restaurants, ii) considering varying air temperatures and humidity, iii) examining speech-related respiratory flows, and iv) employing visual and accurate tools to investigate particle-laden airflow. These insights aim to enhance public health guidelines and building designs to reduce the risk of airborne diseases.

People living in urban and industrialized societies, which are expanding globally, spend more than 90% of their time in the indoor environment, breathing indoor air (IA). Despite decades of research and advocacy, most countries do not have legislated indoor air quality (IAQ) performance standards for public spaces that address concentration levels of IA pollutants (1). Few building codes address operation, maintenance, and retrofitting, and most do not focus on airborne disease transmission. But the COVID-19 pandemic has made all levels of society, from community members to decision-makers, realize the importance of IAQ for human health, wellbeing, productivity, and learning. We propose that IAQ standards be mandatory for public spaces. Although enforcement of IAQ performance standards in homes is not possible, homes must be designed and equipped so that they could meet the standards.

In the realm of environmental, social, and governance (ESG) reporting, the spotlight typically focuses on factors like carbon emissions, social responsibility, and corporate governance. [...]

Airconditioning heeft een negatief imago: het zou ons minder tolerant maken voor temperatuurveranderingen; produceert achtergrondlawaai; zorgt voor tocht; kan de lucht verontreinigen; is moeilijk te bedienen; heeft onderhoud nodig; en gebruikt veel energie. Het is echter in principe economisch mogelijk om installaties te maken en in stand te houden die zowel energetisch verantwoord zijn als een gezond en comfortabel klimaat realiseren. De aanbevelingen en informatie in deze gids zijn bruikbaar voor architecten, installateurs, adviseurs, en voor personen die verantwoordelijk zijn voor het onderhoud van een klimaatinstallatie in een niet-industriële omgeving: bijvoorbeeld je eigen woonomgeving, op school of in een kantoorsituatie!

Mobile air cleaners (MACs) have been proposed as a supplementary solution to combat the spread of respiratory aerosols in school classrooms. To determine which, where and how to use MACs, seven small- and medium-sized MACs were selected and assessed for different settings and configurations by 1) a decay test for determining the clean air delivery rate (CADR), and 2) a perception test with a panel of subjects, together with physical measurements, of noise and air movement. The findings show that to achieve the desired CADR (appr. 1000 m3/h for 30 students per classroom), the key factors are the induced airflow pattern and the location of the MACs. MACs with an upward air supply toward the occupied zone showed much higher CADR (max. 775–1332 m3/h) than those with a horizontal air supply (max. 219–333 m3/h). Moreover, using multiple devices simultaneously was crucial when the room size was increased, and combining mechanical ventilation could improve aerosol removal. Achieving a sufficient CADR would always lead to a noise level above the limit of 35 dB(A), yet sometimes the rating of the panel was more than 50% acceptable. The air velocities mostly fulfilled the requirement (<0.2 m/s), which aligned with the positive panel assessment. Hence, the evaluation by a panel of subjects can help to optimize the use of MACs in a classroom.

Indoor air quality (IAQ) is an important aspect of maintaining human health and well-being, particularly since people spend most of their time indoors. Carpets, with their large surface area and dense fibre piles, have the potential to significantly impact IAQ by emitting and absorbing volatile organic compounds (VOC) from building materials and human activities. The cleaning effect of wool carpets regarding the sorption of odours from two sources of pollution: hardboard and sweaty underwear (as a proxy for bio-effluents), was investigated with an untrained panel of subjects assessing the odour intensity and the acceptability. Tests were performed in three different test environments, including a sniffing table, CLIMPAQs, and full-scale test chambers. The outcome showed that wool carpets can potentially clean the air of odours in small-scale environments, where the wool carpet covers the floor and walls of the test environment, and the odour sources are in contact with the wool carpet. However, the results were less conclusive in on scale scenarios where wool carpets only covered the floor. Overall, wool carpets have the potential to ad(b)sorb odorous emissions, but only when these emissions are near the wool carpet, and thus can have the opportunity to be ad(b)sorbed.

To investigate the feasibility of using mobile air cleaners (MACs) in school classrooms for reducing respiratory aerosols, a test on aerosol removal of seven different types of MACs was conducted in a university classroom, for the optimal condition determined by a prior experimental study. Most of the MACs achieved a good level of clean air delivery rate (CADR) (900-1000 m3/h), and the CADR increased with the number of devices used. Based on the results, three MACs were further selected for conducting an ongoing field study in 45 classrooms at five Dutch primary schools. Each classroom was assigned one type of MAC with two devices, and was monitored for a period of six weeks with three weeks the devices turned on and three weeks off. The assessments of feasibility are based on measurements of indoor air quality, information on absenteeism of the pupils, and interviews with the occupants. The results are yet to be collected to draw further conclusions. However, problems were already encountered during the installation process of the devices which hindered the realization of the pre-determined strategies.

The corona pandemic underlined a lack of Indoor Air Quality (IAQ) and ventilation. Consequently, to limit the spread of the virus, researchers explored several indicators that, through different approaches, assess IAQ and ventilation performance in indoor spaces. This paper gives an overview of those indicators and assessment methods used to evaluate IAQ and ventilation regimes focusing specifically on airborne pathogens. This review considers studies from before and during the COVID-19 pandemic. The indicators found fit into three categories: dose, building, and occupant-related indicators. Studies exploring assessment methods found in this review are grouped according to their themes: aerosol dispersion, ventilation, infection risk, design parameters, and human behaviour. The review showed a need for a holistic definition for IAQ indicators that includes all indicators and a holistic approach of studying IAQ including all five themes.

During the COVID-19 pandemic, the importance of ventilation was widely stressed and new protocols of ventilation were implemented in school buildings worldwide. In the Netherlands, schools were recommended to keep the windows and doors open, and after a national lockdown more stringent measures such as reduction of occupancy were introduced. In this study, the actual effects of such measures on ventilation and thermal conditions were investigated in 31 classrooms of 11 Dutch secondary schools, by monitoring the indoor and outdoorCO2 concentration and air temperature, both before and after the lockdown. Ventilation rates were calculated using the steady-state method. Pre-lockdown, with an average occupancy of 17 students, in 42% of the classrooms the CO2 concentration exceeded the upper limit of the Dutch national guidelines (800 ppm above outdoors),while 13% had a ventilation rate per person (VRp) lower than the minimum requirement (6 l/s/p). Post lockdown, the indoor CO2 concentration decreased significantly while for ventilation rates significant increase was only found in VRp, mainly caused by the decrease in occupancy (average 10 students). The total ventilation rate per classrooms, mainly induced by opening windows and doors, did not change significantly. Meanwhile, according to the Dutch national guidelines, thermal conditions in the classrooms were not satisfying, both pre and post-lockdown. While opening windows and doors cannot achieve the required indoor environmental quality at all times, reducing occupancy might not be feasible for immediate implementation. Hence, more controllable and flexible ways for improving indoor air quality and thermal comfort in classrooms are needed.

Students are exposed to various environmental stimuli at their home study places. However, different students have different preferences in terms of indoor environmental quality (IEQ) aspects and psychosocial aspects of these places. A previous study on students' preferences of their study places resulted in nine profiles based on their IEQ and psychosocial preferences of their study places. It was found that there are profiles that were not highly concerned with sounds at their study places, while other profiles are concerned about sounds. Accordingly, this present study aims at clustering students based on their acoustical-related preferences of their study places. A questionnaire survey was completed by 451 first-year bachelor students at the Faculty of Architecture and the Built Environment at TU Delft. TwoStep cluster analysis was performed, and five unique profiles were identified. These are: 1) sound extremely concerned introvert, 2) sound unconcerned introvert, 3) sound partially concerned introvert, 4) sound concerned extrovert, and 5) sound unconcerned extrovert. The outcomes of this study showed that TwoStep cluster analysis facilitate researchers to better understand the different profiles of students based on their acousticalrelated preferences in study places.

The COVID-19 pandemic highlighted the importance of indoor air quality (IAQ) and ventilation, which researchers have been warning about for years. During the pandemic, researchers studied several indicators using different approaches to assess IAQ and diverse ventilation systems in indoor spaces. To provide an overview of these indicators and approaches in the case of airborne transmission through aerosols, we conducted a literature review, which covered studies both from before and during the COVID-19 pandemic. We searched online databases for six concepts: aerosol dispersion, ventilation, air quality, schools or offices, indicators, and assessment approaches. The indicators found in the literature can be divided into three categories: dose-, building-, and occupant-related indicators. These indicators can be measured in real physical spaces, in a controlled laboratory, or modeled and analyzed using numerical approaches. Rather than organizing this paper according to these approaches, the assessment methods used are grouped according to the following themes they cover: aerosol dispersion, ventilation, infection risk, design parameters, and human behavior. The first finding of the review is that dose-related indicators are the predominant indicators used in the selected studies, whereas building- and occupant-related indicators are only used in specific studies. Moreover, for a better understanding of airborne transmission, there is a need for a more holistic definition of IAQ indicators. The second finding is that although different design assessment tools and setups are presented in the literature, an optimization tool for a room’s design parameters seems to be missing. Finally, to efficiently limit aerosol dispersion in indoor spaces, better coordination between different fields is needed.

Recent studies have shown that both personal and building-related factors may affect the health and comfort of occupants in their homes. It is also known that people differ in their needs and can therefore respond differently to these stressors. Therefore, based on the large database from the survey conducted yearly from 2016 to 2020 among the first-year students of the faculty of Architecture and the Built environment at the Delft University of Technology, this study aimed to explore the associations between self-reported rhinitis/stuffy nose/migraine/headache, and the indoor environment of the students' homes, taking into account potential confounders and profiles. Two-steps cluster analysis resulted in three profiles of students based on their IEQ-related perceptions: Cluster 1 with the highest reported percentage of symptoms and the lowest reported percentage of diseases; Cluster 2 with moderate reported symptoms and diseases; and Cluster 3 with the lowest percentage of reported symptoms and the highest percentage of reported diseases. Logistic regression modelling showed that risk factors contributing to having rhinitis, stuffy nose, migraine and/or headache, differ per cluster, and showed little overlap with the all-respondents group. Moreover, when there is an overlap, the associated risk factor might increase the risk for one cluster, while for another it decreases the risk, indicating differences in response between the different clusters; and therefore, the importance of clustering instead of considering all respondents as one.

This is an account that should be heard of an important struggle: the struggle of a large group of experts who came together at the beginning of the COVID-19 pandemic to warn the world about the risk of airborne transmission and the consequences of ignoring it. We alerted the World Health Organization about the potential significance of the airborne transmission of SARS-CoV-2 and the urgent need to control it, but our concerns were dismissed. Here we describe how this happened and the consequences. We hope that by reporting this story we can raise awareness of the importance of interdisciplinary collaboration and the need to be open to new evidence, and to prevent it from happening again. Acknowledgement of an issue, and the emergence of new evidence related to it, is the first necessary step towards finding effective mitigation solutions.