1EPA United States

Environmental Protection

Agency

EPA 430-F-03-001

Smart Growth and 

Urban Heat Islands

evelopment patterns of the 

last 50 years have had both 

positive and negative impacts

on communities across the country. 

One concern has been steadily 

increasing urban temperatures due to

the effects of “urban heat islands.” A 

heat island is an umbrella of air, often 

over a city or built-up area, that is 

warmer than the air surrounding it. 

The urban heat island profile shown

here demonstrates that heat islands 

are typically most intense over dense 

urban areas. The profile also shows

how parks and other vegetated 

sections within a downtown area may 

help to reduce heat islands. 

In general, summertime heat islands

raise air conditioning demand, air

pollution levels (particularly smog),

and greenhouse gas emissions. They

also increase the incidence of heatrelated illness and mortality. In fact, in

an average year, approximately 1,100 

Americans die from extreme heat --

the leading weather-related killer in the 

United States. 2

Heat islands augment this public

health threat by directly increasing

temperature and indirectly raising 

ground-level ozone concentrations. 

Those at significant risk from extreme

heat and ozone exposure include the 

elderly, children, and individuals with 

pre-existing respiratory disease. 

Residents who live in homes with

dark-colored roofs and no air

conditioning may also be more

vulnerable than the general 

population.

S m a r t G r o w t h F a c t s h e e t S e r i e s

Because urban design plays a large 

role in heat island formation, smart 

growth development strategies provide

an opportunity to reduce heat islands. 

Smart growth is development that 

enhances both a community’s economy 

and environment through strategies to

help citizens make informed decisions

about how and where they want to 

grow. 

In addition to mitigating the heat island 

effect, smart growth provides a

framework for increasing regional 

environmental protection, enhancing 

community character, and 

strengthening local economies. Here 

are four smart growth solutions that can

achieve these goals:

z Reducing off-street parking and 

using porous paving materials:

Surface parking lots replace natural

vegetation with pavements that 

transfer heat to the surroundings. 

Providing on-street parking and 

planning compact, pedestrianoriented development promotes

transportation choices and can

minimize the size and number of

parking lots. 

z Planting, preserving, and 

maintaining trees and vegetation:

Trees and vegetation contribute to

the beauty, distinctiveness, and 

material value of communities by 

incorporating the natural 

environment into the built 

environment. In addition, they cool

surrounding areas by increasing

evapotranspiration – a natural 

process that draws heat from the air

to convert water in the leaf structure 

to water vapor. Planted adjacent to 

homes and buildings, trees provide 

shade, cool the interior, and reduce 

air conditioning energy demand. 

Trees and vegetation planted along 

medians and sidewalks can

decrease evaporative emissions 

from cars and filter pollution from

the air. Rooftop gardens, or green

Everyone wins. Residents get better homes, lower energy bills, and 

cooler neighborhoods with plenty of green space. Narrower streets and a

shorter pipeline means lower installation costs, so the developer gets a 

subdivision that’s cheaper to build. And the City ends up with less streets 

to maintain and a standard for future development that maintain the

community’s existing high quality of life.

J.D. Hightower, City Planner for Escalon, CA 

Currents – An Energy Newsletter for Local Governments January/February 1999

Source: EPA 1992 1

D
S m a r t G r o w t h F a c t s h e e t S e r i e s

“EPA's mission is to protect public health and the environment. EPA works with state and local decision makers to evaluate, promote, and implement 

integrated, common-sense strategies that capitalize on public health and air quality improvements, while encouraging economic growth. Studies have

demonstrated that mitigating heat islands provide clear environmental and financial benefits including improved local and global air quality, reduced heatrelated illness and death, and increased energy savings.”

Case Study

Chicago is a leader in urban forestry and heat island mitigation. The city 

has adopted an open space impact fee ordinance that requires new 

residential development to contribute a proportionate amount of open

space or recreational facilities, or to pay fees that ensure community 

residents of continued access to greenspace. Chicago also replaced a

10,080 ft2 conventionally paved alley with a light-colored permeable

gravel pave system, which has eliminated chronic flooding without

requiring the installation of a sewer system. In addition, between 1991 to

1998 Chicago planted over 500,000 trees and achieved a citywide tree

count of 4.1 million. Chicago's Bureau of Forestry now plants a minimum 

of 5,000 new trees per year and plans to install -- in addition to 120 miles 

of existing median planters -- 280 miles of new median planters by 

2005. In June 2001, Chicago amended its energy code to include 

requirements for reflective or green roofs. See:

http://www.cityofchicago.org/Environment/

To learn more about Smart Growth and the Smart Growth 

Network, please go to http://www.smartgrowth.org.

roofs, can also mitigate urban heat 

islands while increasing the energy 

efficiency and attractiveness of 

commercial and residential 

buildings.

1 “Cooling Our Communities – A Guidebook On Tree Planting and Light-Colored Surfacing”

U.S. Environmental Protection Agency 22P-2001, January 1992.

2 Kalkstein, LS, 1993. Health and Climate Change: Direct Impacts in Cities. The Lancet 

342:1397-99.

3 Stone, B., and M.O. Rodgers. 2001. “Urban Form and Thermal Efficiency: How the Design 

of Cities Influences the Urban Heat Island Effect.” Journal of the American Planning 

Association 67 (2) 186-198. 

Resources

For more information on heat islands, see www.epa.gov/heatisland, 

www.hotcities.org, and http://eetd.lbl.gov/HeatIsland. 

For more information on smart growth, see www.smartgrowth.org and 

www.epa.gov/smartgrowth. Additional information on the relationship 

between the environment and the built environment can be found in 

“Our Built and Natural Environments: A Technical Review of the 

Interactions between Land Use, Transportation, and Environmental

Quality.” EPA 231-R-01-002.

z Promoting infill and higherdensity development:

Development within existing 

communities can preserve open 

space and help offset heat islands 

and their consequences. A 2001 

report found that for every acre of 

brownfield redevelopment, 4.5 

acres of open space is preserved. 

Additional research found that 

compact development contributes 

less heat energy to the 

surrounding air than low-density 

dispersed growth patterns.3

z Increasing public education and 

outreach: Heat island mitigation 

strategies should reflect local 

variation in the built environment, 

as well as local preferences and 

attitudes. Policies should be 

tailored to meet these needs, 

based on stakeholder input, and 

effectively communicated to the 

public. Committees formed to 

address urban heat mitigation 

should include representatives 

from citizen groups, local 

government, non-governmental 

organizations, universities, and 

others concerned about how the 

community grows. A lead 

organization should be appointed 

to disseminate information to the 

community, solicit feedback, and 

incorporate issues and concerns

Office of Air and Radiation (MC 

6205J)

Office of the Administrator (MC 

1808)

EPA 430-F-03-001

into action plans. Working together, communities can address urban 

heat islands while enhancing the quality and character of their 

neighborhoods. 

2 Printed on 100% recycled/recyclable paper with a minimum 50% post-consumer fiber using vegetable-based ink.