Delivering Urban Resilience: Costs and benefits of city-wide adoption of smart surfaces
This report quantifies the benefits and costs of smart surface technologies and finds that the risks from extreme heat and weather can be offset by these technologies. It draws on Washington D.C., Philadelphia, and El Paso as case studies and considers five smart surface technologies: cool roofs, green roofs, solar PV, reflective pavements, and urban trees. The authors find that adopting these technologies can generate millions (or even billions) of dollars in net financial benefits at the city level and can generate half a trillion dollars in net financial benefits nationwide. It also finds that benefits are greatest in low-income areas.
The report first provides background information about the urban heat island (UHI) effect, climate change projections, and smart surface technologies. Cities usually have higher temperatures and worse air quality than surrounding areas, primarily due to the replacement of natural surfaces with urban surfaces. As the climate changes, Washington D.C., Philadelphia, and El Paso are all expected to experience warmer weather, which would exacerbate UHI effects. In addition, the report provides a general description of the five smart surface technologies reviewed and the benefits each technology would bring, such as lower greenhouse gas emissions and fine particle pollution, job creation, relieving pressure on stormwater infrastructure, and avoiding summer tourism loss.
The report spotlights three low-income areas - Ward 5 in Washington D.C., North Philadelphia, and a low-income region in El Paso - and shows that these low-income areas can secure millions of dollars in net present value (NPV) over 40 years as smart surface technology deployment scales up. These low-income areas have more impervious surfaces and 30% lower tree coverage relative to the cities as a whole, which contributes to worse air quality, more health problems, and higher energy bills. Adopting smart surface solutions can address this systematic inequality and offer significant benefits. The payback time for these solutions does vary. Cool roofs offered fast payback in all cases, while other solutions varied by city.
Additionally, if city programs are well structured, two-thirds of jobs that accrue from supporting smart surface solutions can benefit low-income residents.
The report further illustrates the working principles and an in-depth cost and benefit analysis of each smart surface technology. For example, cool roofs can reflect more sunlight and absorb less solar radiation than conventional roofs. Two major costs associated with cool roofs include the installation of the roof and their ongoing maintenance. While the authors find that the installation does, in fact, cost more than conventional roofs, their analysis finds that maintenance requirements are equivalent. Major benefits include ambient cooling, greenhouse gas emission reductions, air quality and health improvements, and increased roof life.
Another smart surface technology reviewed is the use of urban trees. Important factors for an effective tree-planting program are sufficient soil volume and tree selection. Major costs include purchasing, planting, and maintaining trees. For example, the estimated planting cost for Washington D.C. and Philadelphia is $360 per tree. For El Paso it is $150 per tree. The estimated maintenance cost for Washington D.C. and Philadelphia is $13 per tree per year. For El Paso it is $7 per tree per year. However, urban trees also provide substantial benefits, including energy savings, ambient cooling, greenhouse gas emissions reductions, air quality improvements, and reduced stormwater runoff.
The report concludes with summary tables including detailed estimation of the costs and benefits of each smart surface technology in the three cities and three low-income areas. For example, the report estimates that the NPV of the cumulative economic impact would be $47.4 million if green roofs were adopted in Ward 5 in Washington D.C. The NPV would be $281 million if they were adopted citywide.
Publication Date: 2018
Authors or Affiliated Users:
- Greg Kats
- Keith Glassbrook
- Policy analysis/recommendations