The Urban Heat Island Mitigation Impact Screening Tool (MIST)

A web-based software tool has been developed to assist urban planners and air quality management officials in assessing the potential of urban heat island mitigation strategies to affect the urban climate, air quality, and energy consumption within their cities. The user of the tool can select from over 170 US cities for which to conduct the analysis, and can specify city-wide changes in surface reflectivity and/or vegetative cover. The Mitigation Impact Screening Tool (MIST) then extrapolates results from a suite of simulations for 20 cities to estimate air temperature changes associated with the specified changes in surface characteristics for the selected city. Alternatively the user can simply define a nominal air temperature reduction that they hope to achieve with an unspecified mitigation scenario. These air temperature changes are then input to energy and ozone models to estimate the impact that the mitigation action may have on the selected city. The results presented by MIST include a high degree of uncertainty and are intended only as a first-order estimate that urban planners can use to assess the viability of heat island mitigation strategies for their cities. As appropriate, MIST analyses should be supplemented by more detailed modeling

The Effect of Microencapsulated Phase-Change Material on the Compressive Strength of Structural Concrete

Latent heat energy storage through phase-change materials (PCMs) is one possible strategy to control interior temperatures in buildings, improve thermal comfort, and passively reduce building energy use associated with heating and cooling. While PCMs integrated into building structure elements have been studied since the 1970s, challenges of integrating PCMs into building materials while maintaining their heat storage benefits have limited their application in practice. The recent introduction of microencapsulated phase-change materials provides the energy storage capability of PCMs in micron-scale, chemically-inert capsules that can be easily integrated into composite materials such as gypsum wallboard and concrete. The size and physical properties of microencapsulated PCMs suggest that they will behave similarly to filler materials in concrete. Such filler materials are generally less than 125 μm in diameter and can increase concrete strength when added to a mix. This study uses the compressive strength of hardened concrete mixes with varying amounts of PCM to evaluate the effect of PCM addition on concrete structural integrity

Indoor air quality and thermal comfort for elderly residents in Houston TX—a case study

The elderly population is more vulnerable to poor indoor environmental quality. They also spend a larger portion of their time indoors than the general public, further exacerbating the associated health risks. As part of a larger study which aims to understand the health risks for the elderly population resulting from extreme heat events in Houston, TX, this study gathered empirical data on thermal comfort and air quality in existing assisted living facilities and in individual homes of the elderly. We made continuous measurements of indoor dry-bulb temperature, relative humidity, carbon dioxide (CO2) levels and occupancy status in 25 buildings during summer months in 2016 and 2017. Then, using the measured data, we calculated the percentage of hours in which the thermal discomfort index or CO2 levels were above healthy thresholds for each site. Our results show that the indoor discomfort index and/or CO2 level exceeded the safe thresholds for at least 5% of the time in two-thirds of the buildings tested. Considering that research suggests more extreme summer weather in this region in the future, the results of this study highlight the need to consider changes in building management and occupant behavior as well as targeted improvements in the building stock to minimise adverse health impacts. In addition, the results also highlight a potential trade-off between thermal comfort and air quality in these building; air-tightening of the buildings will result in better thermal comfort at the expense of higher CO2 levels, especially in buildings with a higher number of occupants

Development of a National Anthropogenic Heating Database with an Extrapolation for International Cities

Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying anthropogenic heating data, an important component of the urban energy budget for cities across the world. Incorporation of anthropogenic heating data as inputs to existing climate modeling systems has direct societal implications ranging from improved prediction of energy demand to health assessment, but such data are lacking for most cities. To address this deficiency we have applied a standardized procedure to develop a national database of seasonally and diurnally varying anthropogenic heating profiles for 61 of the largest cities in the United Stated (U.S.). Recognizing the importance of spatial scale, the anthropogenic heating database developed includes the city scale and the accompanying greater metropolitan area. Our analysis reveals that a single profile function can adequately represent anthropogenic heating during summer but two profile functions are required in winter, one for warm climate cities and another for cold climate cities. On average, although anthropogenic heating is 40% larger in winter than summer, the electricity sector contribution peaks during summer and is smallest in winter. Because such data are similarly required for international cities where urban climate assessments are also ongoing, we have made a simple adjustment accounting for different international energy consumption rates relative to the U.S. to generate seasonally and diurnally varying anthropogenic heating profiles for a range of global cities. The methodological approach presented here is flexible and straightforwardly applicable to cities not modeled because of presently unavailable data. Because of the anticipated increase in global urban populations for many decades to come, characterizing this fundamental aspect of the urban environment – anthropogenic heating – is an essential element toward continued progress in urban climate assessment

Comparative assessment of night ventilation performance in a nearly zero-energy office building during heat waves in Brussels

peer reviewedWith increasing urbanization, overheating intensifies, resulting in a greater risk of indoor overheating in commercial buildings, which already have high internal gains. The impact of urban climate on the cooling energy needs of buildings has been extensively researched. However, the building performance during extreme heat events needs further investigation to reduce the energy demand from the grid during critical events and to ensure an acceptable indoor thermal environment. Here, a comparative assessment approach for natural and mechanical night ventilation performance to reduce indoor overheating and energy needs of a nearly zero-energy office building in Brussels, Belgium, was evaluated for the heat wave and non-heat wave periods in urban and rural microclimates, using calibrated thermal-energy simulations. The analysis indicated that active cooling with natural night ventilation was more effective during heat waves than other cooling strategies. In addition, natural night ventilation was also effective in maintaining safer levels of heat index values in the reference office compared to other strategies. Natural night ventilation reduced overheating by 0.39 °C in the urban microclimate and 0.50 °C in the rural microclimate relative to the Baseline. Considering the cooling energy use, natural night ventilation had no significant impact. In contrast, mechanical night ventilation increased energy use by 0.54 kWh/m2 in urban microclimate and 0.40 kWh/m2 in rural microclimate due to prolonged ventilation fan operation in the reference office building. The presented findings in the paper lead to the formulation of design guidelines, recommendations for future practices and identifying needs for further research.Project SurChauff

National Urban Database and Access Portal Tool, NUDAPT

Based on the need for advanced treatments of high resolution urban morphological features (e.g., buildings, trees) in meteorological, dispersion, air quality and human exposure modeling systems for future urban applications, a new project was launched called the National Urban Database and Access Portal Tool (NUDAPT). NUDAPT is sponsored by the U.S. Environmental Protection Agency (USEPA) and involves collaborations and contributions from many groups including federal and state agencies and from private and academic institutions here and in other countries. It is designed to produce and provide gridded fields of urban canopy parameters for various new and advanced descriptions of model physics to improve urban simulations given the availability of new high-resolution data of buildings, vegetation, and land use. Additional information include gridded anthropogenic heating and population data is incorporated to further improve urban simulations and to encourage and facilitate decision support and application linkages to human exposure models. An important core-design feature is the utilization of web portal technology to enable NUDAPT to be a Community based system. This web-based portal technology will facilitate customizing of data handling and retrievals (http://www.nudapt.org). This article provides an overview of NUDAPT and several example applications

Improving Livability in Doha: The Role of Neighborhood Microclimates, Land Use, and Materials in Rapidly Urbanizing Regions

Recent evidence suggests that some densely populated areas of the world will be uninhabitable in the coming century due to extreme climate events (e.g. heat waves, atmospheric pollution, and drought) and due to shifts in microclimate and breathable air, which are directly related to livability. With estimates that over 75% of the global population will be living in cities by mid-century, scholars, practitioners, and government officials are asking what cities can do to address the pressing social and environmental challenges that emerge from climate change. They are also seeking to learn how this knowledge may inform policy decisions regarding physical, social, and economic planning to ensure an inviting quality of life and livability in these future places. We believe that we have an unprecedented opportunity to use our knowledge, technology, and social capacities to reduce the likelihood of producing a catastrophic future. This study compares the livability of two seemingly unlikely locations - Doha, Qatar, a capital city on the Arabian Gulf, and Portland, Oregon, an important American city in the Pacific Northwest. These cities are growing at different rates, have diverse cultural histories and varied development patterns, yet are attempting to improve urban livability for citizens in each place and its surrounding region. Through an in-depth examination of the physical changes that have occurred in both places and their corresponding urban climate conditions, especially thermal comfort, we describe the similarities and differences that help to define the challenges facing the management of each. We look specifically at two important empirically-derived measurements of livability: air quality and urban heat island effect. By focusing on these environmental stressors in each place, we are able to evaluate the extent to which different growth and policy drivers have impacted the ability for people to enjoy a desirable quality of life in both cities - different, but appropriate to each. We include as part of our approach a conceptual framework, which describes the coupling of environmental and human conditions for which changes in development patterns have direct implications on the livability of each location. As a result of our analysis, we offer insights about actions that show promise of managing future livability in each city and focus primarily on the ability to manipulate selected aspects of urban form - those characteristics of massing, surface materials, and tree cover that can change the air pollution and urban heat stress experience in each place. We focus specifically on landscape and site scale modifications that show promise of improving air quality and/or reducing urban heat as a stressor. Since cities around the world are looking to nature to provide benefits to city inhabitants, we emphasize the salutary role of green infrastructure. While much is still to be discovered regarding the capacity for cities and their managers to adapt to the emerging challenges of climate change, population growth, and conventional development patterns, yet without sustained and promising actions, the cities that are home to the majority of people today may likely become either obsolete in the coming centuries or present less than desirable living conditions for their future residents. We recognize that while all cities are unique reflections of their unique biophysical, microclimatic, social, cultural, and natural contexts, they also share many similar circumstances and conditions - the identification of which may help policy makers address climate change more effectively. Our conclusions also support the fact that seemingly diverse cities do, in fact, contain similarities in terms of the local, environmental, and urban design conditions that determine air quality and contribute to urban heat island effect.qscienc

The Integrated WRF/Urban Modeling System: Development, Evaluation, and Applications to Urban Environmental Problems

To bridge the gaps between traditional mesoscale modeling and microscale modeling, the National Center for Atmospheric Research (NCAR), in collaboration with other agencies and research groups, has developed an integrated urban modeling system coupled to the Weather Research and Forecasting (WRF) model as a community tool to address urban environmental issues. The core of this WRF/urban modeling system consists of: 1) three methods with different degrees of freedom to parameterize urban surface processes, ranging from a simple bulk parameterization to a sophisticated multi-layer urban canopy model with an indoor outdoor exchange sub-model that directly interacts with the atmospheric boundary layer, 2) coupling to fine-scale Computational Fluid Dynamic (CFD) Reynolds-averaged Navier–Stokes (RANS) and Large-Eddy Simulation (LES) models for Transport and Dispersion (T&D) applications, 3) procedures to incorporate high-resolution urban land-use, building morphology, and anthropogenic heating data using the National Urban Database and Access Portal Tool (NUDAPT), and 4) an urbanized high-resolution land-data assimilation system (u-HRLDAS). This paper provides an overview of this modeling system; addresses the daunting challenges of initializing the coupled WRF/urban model and of specifying the potentially vast number of parameters required to execute the WRF/urban model; explores the model sensitivity to these urban parameters; and evaluates the ability of WRF/urban to capture urban heat islands, complex boundary layer structures aloft, and urban plume T&D for several major metropolitan regions. Recent applications of this modeling system illustrate its promising utility, as a regional climate-modeling tool, to investigate impacts of future urbanization on regional meteorological conditions and on air quality under future climate change scenarios

Meeting reports: Research on Coupled Human and Natural Systems (CHANS): Approach, Challenges, and Strategies

Understanding the complexity of human–nature interactions is central to the quest for both human well-being and global sustainability. To build an understanding of these interactions, scientists, planners, resource managers, policymakers, and communities increasingly are collaborating across wide-ranging disciplines and knowledge domains. Scientists and others are generating new integrated knowledge on top of their requisite specialized knowledge to understand complex systems in order to solve pressing environmental and social problems (e.g., Carpenter et al. 2009). One approach to this sort of integration, bringing together detailed knowledge of various disciplines (e.g., social, economic, biological, and geophysical), has become known as the study of Coupled Human and Natural Systems, or CHANS (Liu et al. 2007a, b). In 2007 a formal standing program in Dynamics of Coupled Natural and Human Systems was created by the U.S. National Science Foundation. Recently, the program supported the launch of an International Network of Research on Coupled Human and Natural Systems (CHANS-Net.org). A major kick-off event of the network was a symposium on Complexity in Human–Nature Interactions across Landscapes, which brought together leading CHANS scientists at the 2009 meeting of the U.S. Regional Association of the International Association for Landscape Ecology in Snowbird, Utah. The symposium highlighted original and innovative research emphasizing reciprocal interactions between human and natural systems at multiple spatial, temporal, and organizational scales. The presentations can be found at ‹http://chans- net.org/Symposium_2009.aspx›. The symposium was accompanied by a workshop on Challenges and Opportunities in CHANS Research. This article provides an overview of the CHANS approach, outlines the primary challenges facing the CHANS research community, and discusses potential strategies to meet these challenges, based upon the presentations and discussions among participants at the Snowbird meeting

A Case-Crossover Analysis of Indoor Heat Exposure on Mortality and Hospitalizations among the Elderly in Houston, Texas

Background: Despite the substantial role indoor exposure has played in heat wave&ndash;related mortality, few epidemiological studies have examined the health effects of exposure to indoor heat. As a result, knowledge gaps regarding indoor heat&ndash;health thresholds, vulnerability, and adaptive capacity persist. Objective: We evaluated the role of indoor heat exposure on mortality and morbidity among the elderly (&ge;65&thinsp;years of age) in Houston, Texas. Methods: Mortality and emergency hospital admission data were obtained through the Texas Department of State Health Services. Summer indoor heat exposure was modeled at the U.S. Census block group (CBG) level using building energy models, outdoor weather data, and building characteristic data. Indoor heat&ndash;health associations were examined using time-stratified case-crossover models, controlling for temporal trends and meteorology, and matching on CBG of residence, year, month, and weekday of the adverse health event. Separate models were fitted for three indoor exposure metrics, for individual lag days 0&ndash;6, and for 3-d moving averages (lag 0&ndash;2). Effect measure modification was explored via stratification on individual- and area-level vulnerability factors. Results: We estimated positive associations between short-term changes in indoor heat exposure and cause-specific mortality and morbidity [e.g., circulatory deaths, odds ratio per&thinsp;5&deg;C&thinsp;increase=1.16 (95% CI: 1.03, 1.30)]. Associations were generally positive for earlier lag periods and weaker across later lag periods. Stratified analyses suggest stronger associations between indoor heat and emergency hospital admissions among African Americans compared with Whites. Discussion: Findings suggest excess mortality among certain elderly populations in Houston who are likely exposed to high indoor heat. We developed a novel methodology to estimate indoor heat exposure that can be adapted to other U.S. locations. In locations with high air conditioning prevalence, simplified modeling approaches may adequately account for indoor heat exposure in vulnerable neighborhoods. Accounting for indoor heat exposure may improve the estimation of the total impact of heat on health. https://doi.org/10.1289/EHP6340</p