The Urban Heat Island Effect Should Force Us to Build Smarter Now Before It's Too Late
Kats & Glassbrook |a Smart Surfaces feature
With more paved area, less greenery and more dark surfaces, cities experience what is called an urban heat island effect - substantially higher summer temperatures and worse air pollution than the surrounding suburban and rural areas. The damage and cost of increased temperature and air pollution are particularly acute for low-income urban areas. In 2005, Environmental Health Perspectives noted that ….
[V]arious aspects of the built environment can have profound, directly measurable effects on both physical and mental health outcomes, particularly adding to the burden of illness among ethnic minority populations and low-income communities.
Low income communities generally share some common attributes …
Air and temperature conditions in low income areas are generally worsened by 1) less tree coverage, 2) fewer reflective and porous surfaces, and 3) more unwanted heat absorption than more affluent city neighborhoods. This results in …
higher summer temperatures,
worse air quality,
increased health problems, and
higher energy bills
… than in more affluent areas. Urban low-income residents also suffer disproportionally from the urban heat island effect and have a higher likelihood of residing in inefficient homes. Health also suffers, and brings cascading costs relating to lost school and work days and reduced income.
The effects of excess heat from climate change on productivity is emerging as an area of public interest. A New York Times editorial entitled “Temperatures Rise, and We’re Cooked” summarized findings that …
[S]tudents who take New York State Residents exam on a 90-degree day have a 12 percent greater chance of failing than when the temperature is 72 degrees. [In auto factories] a week of six days above 90 degrees reduces production by 8 percent.
Low-income schools, neighborhoods, workplaces and homes are more likely to experience this kind of excess heat discomfort and productivity loss.
Many U.S. cities, towns and suburban areas struggle with water quality and stormwater management issues and costs. Consider the Chesapeake Bay, a 200-mile estuary that receives water from 150 major rivers and streams from six states plus Washington, D.C. It is an enormously important watershed in terms of ecological diversity, quality of life, health, tourism and the economy. And like most watersheds, the health of the Chesapeake depends on how urban and built areas upstream manage the rain that falls on them, whether city surfaces are porous and whether smart surface treatments are applied or ignored. The Chesapeake Bay Foundation notes that …
[P]ollution from urban and suburban runoff is the only major source of pollution that is continuing to grow in the Chesapeake Bay watershed… every four years an area of land the size of Washington, D.C., is paved or hardened in the Chesapeake Bay region.
Lack of understanding of the costs and benefits of smart surface technology and policy options has severely limited city policies. This continued analysis is intended to fill this critical gap by quantifying these costs and benefits in detail, including quantifying more than a dozen significant benefits for the first time. By providing an in-depth look at cities such as El Paso, Philadelphia and Washington, D.C., we demonstrate that deployment of smart surface solutions would deliver large city-wide net benefits, including reducing health and energy costs, increasing employment, and enhancing resilience and livability—while reducing contribution to global warming.
Because integrated cost-benefit analysis of these solutions has not previously been done, we can rely on the guidance of national and city partners, epidemiologists, technology, stormwater, energy experts and others, to assemble and analyze U.S. and international data and studies to build a detailed, integrated cost-benefit analysis and financial.
Because it does not exist in the literature, we develop a flow chart for each impact pathway to provide a clear visual representation of causal links between each smart surface technology (such as a cool roof or green roof) and quantified impact (such as increased ozone or reduced CO2 ). In order to simplify quantification of impacts, we include only impacts that are material. For example, Figure 1 below offers an impact pathway diagram, in this case for the impact of increasing rooftop vegetation on ozone concentration ….
Costs (such as operations and maintenance costs), and benefits (such as ozone reduction or job creation) are mapped and calculated for each smart surface technology. These costs and benefits are then aggregated based on modeled ward-wide or city-wide application of these technology solutions for three cities analyzed: El Paso, Philadelphia and Washington, D.C. While we were able to quantify many benefits, other benefits lack sufficient data or rigorous studies to allow quantification, so findings here substantially underestimate total benefits and net present value of adopting these smart surface solutions.
Low-income areas are characterized by higher poverty rates, worse health and higher unemployment. Deployment of smart surface solutions at scale in low-income areas can largely redress this systematic physical urban inequity. Energy costs make up a higher percentage of expenses for low-income residents.
Recent research from the Joint Center for Housing Studies of Harvard University, for example, shows that for the lowest-income renters, tenant-paid household energy costs represent approximately 15 percent of income, while energy costs make up about 1 percent of total income for the highest-income renters. Especially with city training and job linking, jobs created from smart surface solution installations and maintenance could reduce unemployment in low-income areas. Although health benefits from adoption of the solutions analyzed in this report are greater for low-income than for wealthy city residents, these benefits accrue city-wide. For example, excess summer heat in low income areas also heats up the city more generally, while excess heat in low income areas and worse air quality increase emergency room visits by low-income residents, some of whom lack insurance - imposing large costs on city hospitals.
As smart surface deployment scales up, the urban cooling benefits would also grow proportionally, further reducing regional energy bills and smog, and improving health and livability in ways that bring compounding benefits, especially for low-income populations. For example, lower urban heat effects in adjacent regions upwind of Washington, D.C., such as Tysons Corner or Arlington would reduce summer excess heat and smog in those areas and also in Washington, D.C. This phenomenon, which we call “downwind summer cooling”, would bring very large comfort and health benefits both within cities and across larger regions, potentially doubling cooling compared with policies only within city limits. This report does not calculate these downwind summer cooling benefits from accelerating region-wide adoption of these technologies. Additional financial benefits to the cities would likely be large — but are not calculated in this report. However, it is worth noting that low-income neighborhoods are commonly downwind in cities and therefore suffer from excess heating and air pollution. These benefits and the policy implication and opportunities should be more broadly and better understood.
GREG KATS is CEO of the Smart Surfaces Coalition. KEITH GLASSBROOK is Director of Future of Heat Strategy Activation at the National Grid.