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.@en

Throughout history, the human population has experienced major outbreaks of infectious diseases. In December 2019 the previously unknown SARS-CoV-2 virus emerged, which had a huge impact globally. Residents of long- term care facilities (LTCFs) showed to be highly susceptible to infection due to their frailty. Respiratory infectious diseases, such as COVID-19, can spread among others via the airborne transmission route. This is caused by sharing the same indoor environment. To reduce the risk of infection via the airborne route, it is important to consider ventilation and other building services system measures, including personalized ventilation (PV). PV has the potential of being a suitable solution for LTCFs, as it could still allow interaction between residents and visitors in the common rooms, which is regarded very important from a mental health perspective. To identify the potential of PV in the context of infection risk, a laboratory experiment was conducted to investigate its effectiveness on the infection risk reduction. The research was performed in a controlled climate chamber. In the experiment a person was mimicked and positioned close to a PV system that provided filtered recirculated air. A particle source maintained a constant particle concentration in the room. The performance of the PV system was measured through the particle concentration near the breathing zone as compared to the room concentration. Several design parameters were investigated. Translating the outcomes to a fictive (equivalent) ventilation rate, the Wells-Riley equation was applied to determine the infection risk. The outcomes indicated that, in this laboratory setting, the PV system can reduce the risk of an infection up to 50%. The performance is affected by the distance of the supply head to the breathing zone, the angle of the supply head, airflows in the room and the location of the particle source. To further optimize the system and allow its application in LTCFs, several aspects still need further attention, such as mobility/placing the person, the breathing pattern of the user and factors influencing the comfort and use.

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Occupants are often unaware of window-opening strategies that can enhance their well-being and reduce energy consumption. Window feedback systems that indicate when to manually operate a window have become a strategy for enhancing the indoor climate, occupant’s satisfaction and energy efficiency. These systems are recognized for providing the comfort benefits of manual window controls while providing the efficiency benefits of completely automated windows (Bordass et al., 2007; Day et al., 2020). However, there is a lack of evidence to what extent window feedback systems are able to guide occupants towards an effective window operation for both energy and comfort. This research proposes a new window feedback system based on indoor air quality, thermal quality and energy performance. Results from a preliminary testing and deployment are also presented to investigate the effectiveness of the light window feedback system. The outcome of the research shows that ambient light window feedback systems can improve the indoor environment and occupant’s satisfaction in open-plan workplaces. Objective measurements reveal an improved indoor temperature, relative humidity and CO2 concentration. Furthermore, it shows a reduced ineffective window opening time by 55%. Subjective measurements reveal that a majority of the respondents understand the system, do act according to the provided feedback and were satisfied with the implementation. The outcome of this research provides also design requirements for the further development of the light window feedback system and its algorithm.@en

Circularity for Educators’, and a second platform for interaction and direct exchange that we call ‘Educators for Circularity’, are part and parcel of the Circular Impulse Initiative (CII), a project intending to enhance the integration of circularity in BK education. Whereas the first provides with content on either circularity or pedagogy, the latter offers the opportunity for all of us to meet and share our experiences and learn from one another. More than 40 professors and researchers have contributed so far with videos and additional resources that are open and accessible to all. @en

The Dutch government (specifically the ‘Rijksrederij’, the governmental shipping company) owns a fleet of just under 100 ships that are equipped to service the internal waterways and parts of the North Sea. Think in this context of e.g. Coast Guard ships, ships that help to fight oil accidents or ships that maintain buoys. Just after the COVID-19 pandemic had started the ‘Rijksrederij’ decided that it was necessary to investigate to what extent the fleet might pose a risk for cross contamination of this new disease on board. This was approached with a specific focus on ventilation and the airborne route. The objective was to find out whether the most important spaces on board of the ships were adequately ventilated and to evaluate how ships can be made or kept ‘COVID-resistant’ as far as the airborne route is concerned. A sample of 16 ships of different types, most of them mechanically ventilated, were surveyed. This included a general inspection, an inspection of relevant HVAC system characteristics and measurements of e.g. air supply flows. Also, ships were equipped with monitors that measured CO2 concentration (e.g. in galleys and wheelhouses) that were left on board for at least one week. As reference for the supply flow measurement outcomes we used ISO 7547 guideline values and the Germanischer Lloyd ventilation requirements. On board of 6 of the 16 ships that were investigated we found serious problems with the fresh air supply and/or measured CO2 concentrations. On the positive side, the majority of the ships had ventilation capacities in line with the two reference standards, and almost all did not use central recirculation. We also found that many of the ships had adequate options, at room level, for individual control of both fresh air supply and temperature. The results of the study will be used to further improve ‘COVID safety’ on board of the whole fleet and to ameliorate future, new ships and their HVAC systems.@en

Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and aerosol-removal rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend that is consistent with airborne infection and enable recommendations to minimize transmission risk. Transmission in typical prepandemic indoor spaces is highly sensitive to mitigation efforts. Previous outbreaks of measles, influenza, and tuberculosis were also assessed. Measles outbreaks occur at much lower risk parameter values than COVID-19, while tuberculosis outbreaks are observed at higher risk parameter values. Because both diseases are accepted as airborne, the fact that COVID-19 is less contagious than measles does not rule out airborne transmission. It is important that future outbreak reports include information on masking, ventilation and aerosol-removal rates, number of occupants, and duration of exposure, to investigate airborne transmission.@en

A new design method is proposed to calculate outdoor air ventilation rates to control respiratory infection risk in indoor spaces. We propose to use this method in future ventilation standards to complement existing ventilation criteria based on the perceived air quality and pollutant removal. The proposed method makes it possible to calculate the required ventilation rate at a given probability of infection and quanta emission rate. Present work used quanta emission rates for SARS-CoV-2 and consequently the method can be applied for other respiratory viruses with available quanta data. The method was applied to case studies representing typical rooms in public buildings. To reduce the probability of infection, the total airflow rate per infectious person revealed to be the most important parameter to reduce the infection risk. Category I ventilation rate prescribed in the EN 16798-1 standard satisfied many but not all type of spaces examined. The required ventilation rates started from about 80 L/s per room. Large variations between the results for the selected case studies made it impossible to provide a simple rule for estimating the required ventilation rates. Consequently, we conclude that to design rooms with a low infection risk the newly developed ventilation design method must be used.

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During the 2020 COVID-19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID-19 and two died. Transmission by the aerosol route is likely; it appears unlikely that either fomite or ballistic droplet transmission could explain a substantial fraction of the cases. It is vital to identify features of cases such as this to better understand the factors that promote superspreading events. Based on a conditional assumption that transmission during this outbreak was dominated by inhalation of respiratory aerosol generated by one index case, we use the available evidence to infer the emission rate of aerosol infectious quanta. We explore how the risk of infection would vary with several influential factors: ventilation rate, duration of event, and deposition onto surfaces. The results indicate a best-estimate emission rate of 970 ± 390 quanta/h. Infection risk would be reduced by a factor of two by increasing the aerosol loss rate to 5 h⁻¹ and shortening the event duration from 2.5 to 1 h.

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Technological progress in conditioning practice combined with prevailing thermal comfort criteria, created stable, tightly controlled indoor temperature bands. Research shows indoor temperatures to be increasing in the heating period, leading to higher building energy use than planned. Field studies provide proof that occupants not in control of their indoor climate are more dissatisfied and report problems in wellbeing. Widening temperature bands could be an effective measure leading to energy conservation, increasing satisfaction and, as shown recently, helping to mitigate health problems related to our way of life. The adaptive approach to thermal comfort postulates that people's thermal comfort perception adapts to the indoor and outdoor climatic conditions they normally experience. However, according to standards, the adaptive model is applicable only to passively conditioned (free-running) buildings, even though the adaptive principles may well apply also to actively conditioned buildings. Our review found studies demonstrating positive health effects and energy conservation potential in permanently or seasonally conditioned buildings. On this basis, the potential of the adaptive approach and translations into concrete design or operation solutions for actively conditioned buildings are discussed in this paper. We conclude that the adaptive concept offers a potential for indoor climate control in actively conditioned buildings in the temperate and cold climates.

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Exposure to increased concentrations of particulate matter (PM2.5) is related to a higher risk of respiratory and vascular diseases. Indoors, cooking appears to be a major source of PM2.5. In dwellings it has been demonstrated that cooking can lead to concentrations well above the health limits. However, only little is known about the concentrations typically observed in professional kitchens where cooking is the major activity. Therefore, an inventory field study has been set up to measure PM2.5 exposure in the breathing zone of chefs in professional restaurants. In total seven restaurants took part in the study. In all kitchens, PM2.5 exposure in the breathing zone of the chef and at two locations in the kitchen was measured. During the measurements activities of the chef were listed and characteristics of the kitchens were mapped (e.g. open/closed kitchen, type of ventilation, type of food that is prepared). The initial results show that in all restaurants, chefs are exposed to concentrations above the WHO-limit, i.e. average daily exposure of 25 µg/m3. Cooking style, hood and background concentration in the kitchen are factors contributing to the concentration in the kitchen. However, the peak exposure of the chef appears to be highly dependent on behavior and location in relation to the stove and exhaust hoods.@en

During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and direct contact with infected people or contaminated surfaces. While uncertainties remain regarding the relative contributions of the different transmission pathways, we argue that existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors. Appropriate building engineering controls include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation and avoiding overcrowding. Often, such measures can be easily implemented and without much cost, but if only they are recognised as significant in contributing to infection control goals. We believe that the use of engineering controls in public buildings, including hospitals, shops, offices, schools, kindergartens, libraries, restaurants, cruise ships, elevators, conference rooms or public transport, in parallel with effective application of other controls (including isolation and quarantine, social distancing and hand hygiene), would be an additional important measure globally to reduce the likelihood of transmission and thereby protect healthcare workers, patients and the general public.@en

Literature sets personal control over indoor environmental conditions in relation to the gap between predicted and actual energy use, the gap between predicted and observed user satisfaction, and health aspects. A focus on building energy performance often leads to the proposal of more automated and less occupant control of the indoor environment. However, a high degree of personal control is desirable because research shows that a low degree (or no) personal control highly correlates with indoor environmental dissatisfaction and sick building syndrome symptoms. These two tendencies seem contradictory and optimisation almost impossible. Based on current efficiency classes describing the effect of room automation systems on building energy use during operation, fundamental thoughts related to thermophysiology and control, recent laboratory experiments, important lessons learnt from post-occupancy studies, and documented conceptual frameworks on the level of control perceived, we discuss the ambivalence of personal control and how much personal control is adequate. Often-proposed solutions ranging from fully automated controls, over manual controls to dummy controls are discussed according to their effect on a) building energy use during operation and b) occupants perceived control. The discussion points to the importance of adequate personal control. In order to meet the goals for nearly zero energy buildings and for a human-centric design, there is the need to establish design procedures for adequate personal control as part of the design process.

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In 2004 the first adaptive thermal comfort guideline was introduced in the Netherlands. Recently a new, upgraded version of this ISSO 74 (ATG) guideline has been developed. The new requirements are hybrid in nature as the 2014 version of the guideline combines elements of traditional non-adaptive comfort standards with elements of adaptive standards. This paper describes the new guideline and explains the rationale behind it. Also changes in comparison with the original 2004 version and issues related to performance verification are discussed. The information presented in this paper can be used by others (other countries) as inspiration material for other new adaptive comfort guidelines and standards.@en

The OFFICAIR project aimed to describe comfort and indoor air quality (IAQ) in new and retrofitted office buildings in Europe. In France, 21 office buildings participated in this project. In a subsample of five buildings, IAQ measurements and performance tests were carried out to study the relations between IAQ and work performance. Twenty-one compounds were measured (volatile organic compounds, aldehydes, nitrogen dioxide, and ozone) as well as environmental parameters: Carbon dioxide, temperature, and relative humidity, over five days in two different seasons. The occupants in the investigated rooms were invited to participate in two on-line task performance tests: A reaction time test, i.e., the standardized Deary-Liewald test, and a memory test. There were participants in summer and 98 in winter. They also provided self-assessments of the influence of the indoor environment on their productivity. The multilevel linear regression models showed that individual characteristics were the main factors determining performance at work. Indoor air concentrations of xylenes and ozone might influence reaction time during summer. Both in summer and winter, the occupants' satisfaction regarding noise and their perceived ability to control their indoor temperature increased their self-assessed productivity. This work is the first to study the influence of IAQ on performance in real work environments and on the basis of IAQmeasurements. This study was limited to five buildings, but it would be useful to repeat it on a larger scale.@en

A field study was conducted between November 2011 and March 2012 in nine modern office buildings in the Netherlands. One of the objectives was to objectify (under given weather conditions) how much control can be exercised by office workers over their indoor climate with operable windows. To evaluate the effectiveness of the operable windows, dynamic experiments were conducted. The experiments started with the opening of windows by the research team. Next, response times and step responses were assessed in terms of air temperature changes and CO2 concentration alterations. An average maximum outdoor temperature of 8 °C and an average wind speed of 4 m/s were measured during the study. For the cases studied, as far as temperature effects are concerned: the study revealed that the step response on average was -2.2 K; the average halftime value was 8 minutes; and the temperature on average changed with -0.18 K per minute after windows were opened. As far as effects on CO2 concentrations are concerned: step response on average was -390 ppm; the average halftime value was 7 minutes; and the CO2 concentration on average changed with - 37 ppm per minute after windows were opened. With some limitations, the outcomes can be used to quantify how effective operable windows can be -during the heating season- to office building users that periodically want to fine-tune their indoor climate.@en

Field studies suggest that the availability of adjustable thermostats, operable windows and other controls has a positive impact on comfort, the incidence of building related symptoms and productivity. This laboratory study was designed to further investigate how having or not having control over the thermal environment affects human responses to the indoor environment.The study was conducted in summer in a field laboratory that was kept at 28°C. A total of 23 subjects were exposed twice for about 2.5h. During the first session (A) subjects were able to fine-tune their local thermal environment at any given time with a personal desk fan with continuous, stepless adjustable control. During the second session (B) subjects still had the desk fans, but this time the fans were controlled from an adjacent room by the researchers who adjusted the individual air speed profiles so they were identical to those recorded during the first session. Thus, each subject was exposed to two customized conditions with identical exposure, only different from a psychological point of view.During the two sessions identical questionnaires and performance tests were used to evaluate subjects' comfort, SBS symptom incidence and performance. As expected, perceived control over the environment was significantly higher during session A, but there were no differences in perceived comfort and SBS symptom intensity. Both self-assessed and objectively measured performance was significantly better during session B. About two-thirds of the subjects indicated to prefer the situation as during the first session when they themselves controlled the air movement.

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In 2004, the first adaptive thermal comfort guideline was introduced in the Netherlands. Recently, a new, upgraded version of this ISSO 74 (ATG) guideline has been developed. The new requirements are hybrid in nature as the 2014 version of the guideline combines elements of traditional non-adaptive comfort standards with elements of adaptive standards. This paper describes the new guideline and explains the rationale behind it. Also changes in comparison with the original 2004 version and (some) issues related to performance verification are discussed. The information presented in this paper can be used by others (other countries) as inspiration material for new adaptive comfort guidelines and standards.

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A field study was conducted in nine modern office buildings in the Netherlands. The study focused on perceived control over indoor climate and its impact on satisfaction of building occupants, the incidence of building related (SBS) symptoms and self-assessed performance. The study involved a questionnaire amongst 236 office workers. Statistical analyses were conducted to investigate correlations between combined perceived control over temperature and ventilation on the one hand and satisfaction-, SBS- and productivity-indices on the other. Individual perceived control over indoor climate scores were perfectly normally distributed (using a 7 point scale coded from 1 = no control at all to 7 = full control) with as mean value 3.1 (SD 1.4). Respondents that perceived to have a high amount of control over their indoor climate were considerably more satisfied with their indoor environment. High control respondents also had significant less building related symptoms (BSI(5) 0.94 vs. 0.61). And productivity scores were significantly higher (6.3 %point) in comparison with the low control respondents.@en