To understand the exact transmission routes of SARS-CoV-2 and to explore effects of time, space and indoor environment on the dynamics of droplets and aerosols, rigorous testing and observation must be conducted. In the current work, the spatial and temporal dispersions of aerosol droplets from a simulated cough were comprehensively examined over a long duration (70 min). An artificial cough generator was constructed to generate reliably repeatable respiratory ejecta. The measurements were performed at different locations in front (along the axial direction and off-axis) and behind the source in a sealed experimental enclosure. Aerosols of 0.3-10 µm (around 20% of the maximum nuclei count) were shown to persist for a very long time in a still environment, and this has a substantial implication for airborne disease transmission. The experiments demonstrated that a ventilation system could reduce the total aerosol volume and the droplet lifetime significantly. To explain the experimental observations in more detail and to understand the droplet in-air behaviour at various ambient temperatures and relative humidity, numerical simulations were performed using the Eulerian-Lagrangian approach. The simulations show that many of the small droplets remain suspended in the air over time instead of falling to the ground.

Because of COVID-19, the indoor environmental quality (IEQ) in sports facilities has been a concern to environmental health practitioners. To develop an overall understanding of the available guidelines and standards and studies performed on IEQ in sports facilities, an extensive literature study was conducted, with the aim of identifying: (1) indicators that are being used to assess IEQ in different sports facilities; (2) indicators that are potentially interesting to be used to assess indoor air, in particular; (3) gaps in knowledge to determine whether sports facilities are safe, healthy and comfortable for people to stay and perform their activities. The outcome indicates that most current standards and previous investigations on IEQ in sports facilities mainly focused on dose-related indicators (such as ventilation rate), while building-related indicators (such as ventilation regime) and occupant-related indicators (such as IEQ preferences) were rarely considered. Little attention is given to the fact that ventilation systems may play an important role in the air quality of the location, and few investigations have been performed on the transmission of SARS-CoV-2. This study recommends more research into both occupant and building-related indicators as well as cross-modal effects between various IEQ factors for developing future standards on sports facilities.

The airtightness of buildings has a significant impact on buildings' energy efficiency, maintenance and occupant comfort. The main goal of this study is to provide an evaluation of the air leakage characteristics of dwellings in different regions in Canada. This study evaluated the key influencing factors on airtightness performance based on a large set of measured data (73,450 dwellings located in Canada with 11 measurement parameters for each). Machine learning models based on multivariate regression (MVR) and Random Forest Ensemble (RFE) were developed to predict the air leakage value. The RFE model, which shows better results than MVR, was used to evaluate the effect of the ageing of buildings. Results showed that the maximum increase in air leakage occurs during the first year after construction - approximately 25%, and then 3.7% in the second year, after which the increase rate becomes insignificant and relatively constant - approximately 0.3% per year. The findings from this study can provide significant information for building designs, building performance simulations and strengthening standards and guidelines policies on indoor environmental quality.

Heating, Ventilation, and Air-Conditioning (HVAC) system that is almost indispensable service system of modern buildings is recognized as the most important engineering control measure against pandemics. However, the effectiveness of HVAC systems has been questioned on their ability to control airborne transmission. After the outbreak of COVID-19, China has controlled the spread within a relatively short period. Considering the large population, high population density, busy transportation and the overall underdeveloped economy, China's control measures may have some implications to other countries, especially those with limited resources. This paper intends to provide a systematic summary of Chinese ventilation guidelines issued to cope with COVID-19 transmission. The following three aspects are the main focus of these guidelines: (1) general operation and management schemes of various types of HVAC systems, (2) operation and management schemes of HVAC system in typical types of buildings, and (3) design schemes of HVAC system of makeshift hospitals. In addition, some important differences in HVAC guidelines between China and other countries/institutions are identified and compared, and the possible reasons are discussed. Further discussions are made on the following topics, including the required fresh air supply, the extended operation time, the use of auxiliary equipment, the limited capacity of existing systems, and the use of personalized systems.

Nowadays, urban and community resilience have become the core issues of urban theoretical research and construction practices. While there are many studies on climate change, natural hazards and environmental pollution, relatively less attention has been paid to public and human health. However, the current COVID-19 pandemic, which is a major global public health crisis, is posing severe challenges to the resilience of cities and communities in the context of high-mobility, high-density and high-intensity, as well as expands the connotation of community resilience to public health. To compensate for the lack of current research, this study examined the characteristics of community medical facilities in response to pandemics at urban, community and individual multi-spatial scales based on a thorough review of current research and relevant practice. It also emphasized the significant role played by community medical facilities in improving resilient community constructions in the face of large-scale public health emergencies. These characteristics were fully utilized to explore ways to build and govern the 'resilience' of communities in the future, help people to survive better as well as develop in complex and changeable external environments.

This study examines the perceived neighbourhood characteristics and environmental barriers in association with two different types of walking - recreational and destination - in the context of a rural town in Mississippi. A cross-sectional survey was used to assess residents' walking behaviours, perceived neighbourhood characteristics, and perceived environmental barriers to walking in three types of neighbourhoods: traditional, early conventional suburban and late conventional suburban. Descriptive statistics, one-way analysis of variance (ANOVA) and regression analyses identified environmental factors correlated with walking. A total of 362 surveys were completed and returned by random adult members of the households contacted, for a 38.5% response rate. Perceived aesthetics are significantly associated with more frequent recreational and destination walking in this rural town. Higher perceived accessibility are associated with more frequent destination walking, and greater perceived social environment barriers to walking are associated with sedentary behaviour in the rural population studied. Of all factors related to a neighbourhood's built environment, the most important factor in promoting walking in rural towns is aesthetics. The relationships among accessibility, social environment and walking underscore the importance of community planning in incorporating mixed land uses, providing a connected pedestrian infrastructure and facilitating targeted social interventions to encourage more walking.

Cold homes and fuel poverty have been identified as factors in health and social inequalities that could be alleviated through energy efficiency interventions. Research on fuel poverty and the health impacts of affordable warmth initiatives have to date primarily been conducted using quantitative and statistical methods, limiting the way how fuel poverty is understood. This study took a longitudinal focus group approach that allowed exploration of lived experiences of fuel poverty before and after an energy efficiency intervention. Focus group discussions were held with residents from three low-income communities before (n = 28) and after (n = 22) they received energy efficiency measures funded through a government-led scheme. The results show that improving the energy efficiency of homes at risk of fuel poverty has a profound impact on wellbeing and quality of life, financial stress, thermal comfort, social interactions and indoor space use. However, the process of receiving the intervention was experienced by some as stressful. There is a need for better community engagement and communication to improve the benefits delivered by fuel poverty programmes, as well as further qualitative exploration to better understand the wider impacts of fuel poverty and policy-led intervention schemes.

Energy poverty - which has also been recognised via terms such as 'fuel poverty' and 'energy vulnerability' - occurs when a household experiences inadequate levels of energy services in the home. Measuring energy poverty is challenging, as it is a culturally sensitive and private condition, which is temporally and spatially dynamic. This is compounded by the limited availability of appropriate data and indicators, and lack of consensus on how energy poverty should be conceptualised and measured. Statistical indicators of energy poverty are an important and necessary part of the research and policy landscape. They carry great political weight, and are often used to guide the targeting of energy poverty measures - due to their perceived objectivity - with important consequences for both the indoor and built environment of housing. Focussing on the European Union specifically, this paper critically assesses the available statistical options for monitoring energy poverty, whilst also presenting options for improving existing data. This is examined through the lens of vulnerability thinking, by considering the ways in which policies and institutions, the built fabric and everyday practices shape energy use, alongside the manner in which energy poor households experience and address the issue on a day-to-day basis.

Considerable overlap exists between post-occupancy research evaluating building design quality and the concept of 'social value', popularised by its recent application to issues of the public realm. To outline this potential research agenda, the paper reviews design quality research on buildings in relation to users and their social context where the term 'social context' refers to building user group dynamics, a combination of organisational cultures, management strategies, and social norms and practices. The review is conducted across five key building types, namely housing, workplaces, healthcare, education, and the retail/service sector. Research commonalities and gaps are identified in order to build a more comprehensive picture of the design quality literature and its handling of users in their social context. The key findings concerning each building type are presented visually. It is concluded that the design quality field comprises a patchwork of relatively isolated studies of various building types, with significant potential for theoretical and empirical development through interdisciplinary collaboration. Users tend to be conceived as anonymous and autonomous individuals with little analysis of user identity or interaction. Further, the contextual impact of user group dynamics on the relationship between building design and building user is rarely addressed in the literature. Producing a more nuanced understanding of users in situ is proposed as an important area for future design quality research.

Social housing organisations are increasingly installing renewable energy technologies, particularly for the provision of heating and hot water. To meet carbon reduction targets, uptake and installation must allow occupants to use the technology effectively. This paper describes research which investigated the service of installing heat pumps into UK social housing properties, from both landlords' and tenants' experiences. Adopting a user centred design approach, the research was in three phases: an exploration study to investigate landlords' and tenants' experiences of heat pump installation and use; refinement and development of the requirements for improved service delivery, primarily technology introduction and control; and the development and initial evaluation of an information leaflet as a key touchpoint in the service delivery. Recommendations for improved service delivery, to enable heat pumps to be accepted and used more effectively, are presented, as well as reflection on the process of applying user centred design in this context. In a relatively immature area of industry, installations to date have been heavily focused on technical aspects. This paper provides an insight into the human aspects of the service delivery of heat pumps in social housing, providing designers and social housing landlords with insight about how to improve the service.

It has been argued that the amount of time spent by humans in thermoneutral environments has increased in recent decades. This paper examines evidence of historic changes in winter domestic temperatures in industrialised countries. Future trajectories for indoor thermal comfort are also explored. Whilst methodological differences across studies make it difficult to compare data and accurately estimate the absolute size of historic changes in indoor domestic temperatures, data analysis does suggest an upward trend, particularly in bedrooms. The variations in indoor winter residential temperatures might have been further exacerbated in some countries by a temporary drop in demand temperatures due to the 1970s energy crisis, as well as by recent changes in the building stock. In the United Kingdom, for example, spot measurement data indicate that an increase of up to 1.3°C per decade in mean dwelling winter indoor temperatures may have occurred from 1978 to 1996. The findings of this review paper are also discussed in the context of their significance for human health and well-being. In particular, historic indoor domestic temperature trends are discussed in conjunction with evidence on the links between low ambient temperatures, body energy expenditure and weight gain.

Advanced naturally ventilated systems based on integration of basic natural ventilation strategies such as cross-ventilation and stack effect have been considered to be a key element of sustainable design. In this respect, there is a pressing need to explore the potential of such systems to achieve the recommended occupant comfort targets throughout their lifetime without relying on mechanical means. This study focuses on use of a windcatcher system in typical classrooms which are usually characterized by high and intermittent internal heat gains. The aims of this paper are 3-fold. First, to describe a series of field measurements that investigated the ventilation rates, indoor air quality, and thermal comfort in a newly constructed school located at an urban site in London. Secondly, to investigate the effect of changing climate and occupancy patterns on thermal comfort in selected classrooms, while taking into account adaptive potential of this specific ventilation strategy. Thirdly, to assess performance of the ventilation system using the newly introduced performance-based ventilation standards for school buildings. The results suggest that satisfactory occupant comfort levels could be achieved until the 2050s by a combination of advanced ventilation control settings and informed occupant behavior.

Minimum outdoor air ventilation rates specified in standards such as ASHRAE Standard 62.2 are generally based on envelope airtightness, building floor area, geographical location, and number of occupants. ASHRAE Standard 62.2 allows for a constant infiltration credit, which reduces the required mechanical ventilation. However, infiltration rates vary based on the weather and system operation. Thus, mechanical systems could potentially operate less if the real-time (RT) infiltration rate were known and used to adjust the mechanical ventilation rate. CONTAM models of two test houses on the campus of the National Institute of Standards and Technology were verified with measurements and used to simulate hourly infiltration rates in three cities. The infiltration rates were passed to a theoretical controller that changed the hourly mechanical ventilation rate to meet the ventilation requirement. Simulated energy use and relative annual occupant exposure for this RT control strategy was compared with ventilating at a constant rate. Implementation of the RT control strategy resulted in annual average energy savings of $66USD across both houses and three cities without increasing the annual occupant exposure compared with ventilating continuously at a constant rate. The authors discuss the advantages and limitations of the proposed real-time ventilation control strategy.