James Bruggers

Louisville Courier Journal

Louisville's heat island has been growing at one of the fastest rates in the country.

Temperatures within Louisville vary dramatically from one part of a city to another.

Recommendations range from incentives to new regulatory programs.

Heat is a matter of life and death for some.

Heat likely contributed to the deaths of about 86 area residents in the scorcher summer of 2012 - and taking steps to cool Louisville's hot spots could save lives, money and improve living conditions for hundreds of thousands, a long-anticipated report concludes.

The study out of Georgia Tech commissioned by city officials assesses the extent to which this region is warming due to urban development and tree loss, it estimates the public health implications and it offers recommendations. The report's author, city and regional planning professor Brian Stone Jr., said the urban heat management study is the first of its kind for any major American city, and it points a path toward a cooler, more liveable community.

"We find that overall, through actions that are achievable through public policy, more than 20 percent of the annual heat-related deaths in Louisville could be avoided," he said in an interview. "We see reductions in summer averages of 1-degree Fahrenheit or more, which is significant when averaged over several months."

Some hot spots could be cooled by as much as 5 degrees, day and night, if city homes and businesses adopt strategies for cooler roofs, cooler streets and planting as many as 450,000 trees.

At issue is something called the urban heat island - the difference between city temperatures and surrounding rural areas. Four years ago Stone's research found that Louisville's heat island was growing at one of the fastest rates in the country, if not the fastest.

Stone's report also shows how temperatures within Louisville vary dramatically from one part of a city to another, depending on land-uses and landscaping, with health and economic consequences. Maps show the differences in a scale as small as about six city blocks. But broadly speaking, downtown, west and southwest Louisville are hottest parts of the city, followed by south and central Louisville, then eastern Louisville.

Neighborhood differences

The report identifies roads and pavement, dark roofs, lack of trees, and waste heat from factories to motor vehicles as culprits.

Using computer modeling techniques, the study found the average difference across Louisville during the warm season was about 5 degrees, at the upper end of a typical range across numerous American cities. During the hot summer of 2012, the study found the difference between the hottest and coolest areas of Louisville sometimes exceeded 12 degrees.

All that extra heat has consequences, including matters of life and death.

Relying on a statistical analysis of excess mortality and temperature, the study estimated that 86 residents died of heat-related illnesses during the 2012 warm season of May through September. They blamed roughly two-thirds of those - 53 - on the city's urban heat island that year.

Their study pegged the highest zones of mortality clustered inside the Watterson Expressway but with some significant zones between the Watterson and Interstate 265, and west of the Louisville International Airport.

Stone said Louisville could expect more heat-related deaths than that in some years, and fewer in others. Overall, he said, people often don't fully appreciate how heat can exacerbate someone's underlying health condition, such as heart or respiratory illness, sometimes contributing to their demise.

Louisville officials have scheduled a 10:30 a.m. news conference at Metro Hall with Mayor Greg Fischer to discuss the study and talk about what comes next.

Tree ordinance called for

Fischer spokesman Chris Poynter said the city will open a 60-day public comment period while it discusses its policy options internally and deciding what the city can do, and how it can encourage residents and businesses to join the effort.

"The value is in having the data, and understanding what can be implemented on a neighborhood scale," said Maria Koetter, Louisville's sustainability director. City officials plan to post the report online, and residents will be able to look up their neighborhoods' vulnerability and what opportunities they have to fight the heat.

The report makes a variety of recommendations, including echoing a recommendation from the disbanded Louisville tree advisory committee: adopt a comprehensive tree ordinance.

Interactive | Louisville's tree canopy and heat map

A proposed tree-protection ordinance for trees on public land and rights-of-ways has been with the mayor's staff for 10 months now. City officials also have been deadlocked for four years over whether to tighten, loosen or maintain tree protection requirements for developers on private property.

"Louisville needs to increase its tree canopy rather significantly," Stone said. "It's hard to do that if you are not preserving what you have."

Poynter said the mayor intends to propose a tree ordinance to metro council later this year.

No cost estimates

Other recommendations in the report include considering new policies requiring roofs that reflect heat, such as those that are white or lighter colored, lighter-colored or more reflective road and parking lot surfaces, vegetated roofs, and policies that get more people to adopt energy efficiency measures to limit waste heat from factories, businesses, cars and trucks.

The Georgia Tech study did not estimate costs of carrying out its recommendations.

Koetter said city officials are developing a tree management plan with specific tree planting goals later this year. That report follows a tree canopy study from last year that estimated a $1.7 billion tree-planting price tag over 40 years to reach a canopy coverage goal of 45 percent over Louisville’s 398 square miles, more like tree coverage in Atlanta and Charlotte.

That study pegged the current canopy coverage at 37 percent and found if nothing is done, it could fall to 21 percent by 2052.

Reach reporter James Bruggers at (502) 582-4645 and at jbruggers@courier-journal.com.

Why tackle heat?

Heat kills and not just by heat stroke. People with heart, lung and other ailments can suffer severely during heat waves.

Heat increases maintenance and repair costs for roads and railroad tracks.

Heat costs homes and businesses money for air conditioning.

Heat hinders aircraft liftoff performance.

Excessive heat can cause blackouts and put a strain on drinking water resources.

What can we do?

Switch to cool roofing materials, especially in industrial and commercial zones. Cool roofs are often white and are highly reflective of solar radiation, and they can save energy and money.

Explore cool paving options. Porous parking lots that absorb water are cooler that black asphalt. Look for new types of road surfaces that are more reflective as possible alternatives to asphalt.

Plant trees and maintain trees, especially in residential areas where exposure to heat is greatest.

Step up efforts to encourage homes and businesses to be more energy efficient.

Combine strategies for the biggest reduction of heat.

Consider a combination of regulatory and economic incentive programs to move the community to a cooler future.

Source: Louisville Heat Management Study