New study says Louisville Ky is hot and getting hotter faster than other US cities


Study outlines strategies to combat urban heat island and improve city’s health

Decades-long effort include city government, citizens, businesses working together


Note: The city has created a special website where citizens can search for data about their neighborhood. The site also contains the heat island study, videos about strategies to reduce the heat island, and ways for citizens to comment on the findings.


LOUISVILLE (April 25, 2016) — Louisville’s urban core is warming more than outlying areas at a faster rate than in other American cities, threatening the health of all citizens — especially the young and elderly. But there are actions the city can take to reduce the impact, according to a new study released today by Mayor Greg Fischer and the city’s Office of Sustainability.

The urban heat island — defined as a city or metropolitan area that’s significantly warmer than its surrounding rural areas — contributes to heat-related illnesses and death and leads to higher air-conditioning bills for everyone, according to the study by Dr. Brian Stone, of the Georgia Institute of Technology.

Louisville Skyline

“The urban heat island has serious implications for our citizens. It impacts our health, our economy – from your wallet, to our talent attraction efforts, to costs for our businesses – and our overall quality of life,” Fischer said. “The hotter air exacerbates the effect of air pollution and causes problems for people with asthma and other breathing conditions.”

The study determined that 86 citizens in Louisville die every year due to heat-related ailments.

“We know that too often the ZIP code where you are born can correlate with negative health outcomes. That’s unacceptable,’ Fischer said. “In addition, the added heat causes citizens and businesses to run their air-conditioners longer and higher, which drives up energy costs for citizens and businesses, while also increasing pollution, leading to more global warming.  It’s a vicious cycle.”

The city can reduce the heat island through simple but effective strategies that can be implemented by city government, citizens and businesses, the study found. Those strategies fall into two categories — cooling and greening — and include:

  • Installing cool roofs, especially on commercial buildings that have flat roofs. Cool roofs are white or light-colored, as opposed to the traditional black roof. Cool roofs reflect sun, rather than absorb it — and that reduces energy costs. Louisville International Airport, for example, has been installing cool roofs.
  • Installing green roofs that use plants and grasses, rather than rubber or tar. A green roof, such as the one atop the American Life Building at Fifth and Main streets or atop the Metro Development Center at 444 S. Fifth Street, has the added benefit of improving air quality, soaking up rainwater and keeping it out of the sewer system.
  • Coating city streets, currently paved in heat-absorbing blacktop, with a light-colored topping to make them reflect heat. The city will be searching for products to achieve this and conduct tests in the coming months.
  • Planting trees to provide shade, especially in neighborhoods that lack a solid tree canopy. Trees are effective at blocking 70 percent to 90 percent of solar radiation in summer, and 20 percent to 90 percent in winter.
  • Planting grasses on barren lands that have no vegetation or are only dirt.

The study, which Dr. Stone said is the most comprehensive urban heat review undertaken by a large American city, shows that a combination of cooling and greening strategies yield the greatest benefit — but that installing cool roofs is the quickest, most immediate way to combat the heat island.

“For the first time, we have excellent data, down to the neighborhood level, of how to cool our city,” Fischer said. “This is important not only to make Louisville a more sustainable city – it’s important for economic development and attracting a talented workforce. People want to live — and companies want to locate and grow — in a city that is green, healthy and future focused.”

Dr. Stone and his research team mapped the entire city — about 400 square miles — and examined the heat island impact by neighborhood. He also laid out strategies, again by neighborhood, to reduce the heat island.

For example, Old Louisville could reduce the urban heat island effect there by planting 7,348 trees and installing 517 white roofs.

The city has created a special website where citizens can search for data about their neighborhood. The site also contains the heat island study, videos about strategies to reduce the heat island, and ways for citizens to comment on the findings.

Maria Koetter, the city’s Director of Sustainability, said the public will have 60 days to comment on the study through a variety of methods, including the website and via social media (Facebook: Sustain Louisville). Dr. Stone will also deliver a lecture about his findings at 6 p.m.May 16 at Egan Leadership Center at Spalding University, 901 S 4th St. The event is free and open to the public.

After the 60-day period, the city and others are expected to announce policy changes in city government to begin the long-term process of reducing the city’s heat island.

The heat island study was funded with private dollars from the Owsley Brown Foundation and the Augusta Brown Holland Foundation, and is part of Sustain Louisville, the city’s sustainability plan. The study supplements another major study, the Tree Canopy Assessment, which was released last year and found the city is losing about 54,000 trees annually.

The heat island study is part of the city’s broader strategy to make the city more sustainable. Other recent announcements and policy efforts by the city:

  • The unveiling of the Move Louisville 20-year transportation plan for the city, with a goal of reducing vehicle miles traveled and providing citizens with multiple options for moving around the city;
  • The signing of the climate Compact of Mayors, with the city and businesses pledging to reduce greenhouse gas emissions;
  • The creation of Trees Louisville, the non-profit dedicated to raising money to plant trees and increase the city’s depleted canopy;
  • The announcement that the city will not mow vacant lots, parks and right of way on Air Quality Alert Days.