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Reducing Urban Heat Islands:
Compendium of Strategies
Heat Island Reduction Activities
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Acknowledgements
Reducing Urban Heat Islands: Compendiu m of Strategies describes the
causes and impacts of summertime urban heat islands and promotes
strategies for lowering temperatures in U.S. communities. This compendium
was developed by the Climate Protection Partnership Division in the U.S.
Environmental Protection Agency's Office of Atmospheric Programs. Eva
Wong managed its overall development. Kathleen Hogan, Julie Rosenberg,
and Andrea Denny provided editorial support. Numerous EPA staff in
offices throughout the Agency contributed content and provided reviews.
Subject area experts from other organizations around the United States and
Canada also committed their time to provide technical feedback.
Under contracts 68-W-02-029 and EP-C-06-003, Perrin Quarles Associates,
Inc. provided technical and administrative support for the entire
compendium, and Eastern Research Group, Inc. provided graphics and
production services.
PositvEnergy provided support in preparing the Trees and Vegetation, Cool
Roofs, and UHI Activities chapters under contract PO #2W-036 l-SATX.
Experts who helped shape this chapter include:
David Cole, Nikolaas Dietsch, Gary Gero, David Hitchcock, Megan Lewis,
Julie Magee, Misha Sarkovich, Jim Yarbrough, and Barry Zalph.
Suggested Citation: U.S. Environmental Protection Agency. 2008. "Heat
Island Reduction Activities." In: Reducing Urban Heat Islands:
Compendium of Strategies. Draft, https://www.epa.gov/heat-islands/heat-
island-compendium.
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Contents
Heat Island Reduction Activities 1
1. Voluntary Efforts 2
1.1 Demonstration Projects 2
1.2 Incentives 4
1.3 Urban Forestry Programs 5
1.4 Weatherization 7
1.5 Outreach and Education Programs 8
1.6 Awards 8
2. Policy Efforts 9
2.1 Procurement 9
2.2 Resolutions 10
2.3 Tree and Landscape Ordinances 10
2.4 Comprehensive Plans and Design Guidelines 13
2.5 Zoning Codes 14
2.6 Green Building Programs and Standards 14
2.7 Building Codes 16
2.8 Air Quality Requirements 18
Endnotes 20
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Heat Island Reduction Activities
Across the United States, a diverse group of stakeholders, from government agen-
cies to corporations, have advanced urban heat island reduction strategies—urban
forestry, green and cool roofs, and cool pavements—to lower summertime tempera-
tures and achieve many energy and environmental benefits. Typically heat island mitiga-
tion is part of an energy, air quality, water, or sustainability effort,1 and activities range
from voluntary initiatives, such as cool pavement demonstration projects, to policy actions,
such as requiring cool roofs via building codes. Some communities have elected to imple-
ment both voluntary and policy initiatives. These efforts can complement each other, and
sometimes an initiative that begins as a voluntary activity becomes required over time.
This chapter draws from the experience of many different groups and covers a range of
initiatives to highlight a variety of urban heat island reduction activities around the coun-
try. Examples for the following types of activities are included:
• Demonstration projects
• Incentive programs
• Urban forestry programs
• Weatherization
• Outreach and education
• Awards
• Procurement
• Resolutions
• Tree and landscape ordinances
• Comprehensive plans and design guidelines
• Zoning codes
• Green building standards
• Building codes
• Air quality standards.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
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Heat Island Mitigation
Strategies
For more information on heat island
reduction strategies, see the corre-
sponding chapters of this compendium:
"Trees and Vegetation," "Green Roofs,"
"Cool Roofs," and "Cool Pavements."
1. Voluntary Efforts
Most community strategies to reduce heat
islands have relied on voluntary efforts,
which can generally be grouped into the
following categories:
• Demonstration projects
• Incentive programs
• Urban forestry programs
• Weatherization
• Outreach and education
• Awards.
Many groups choose to conduct just
one kind of activity; others combine ap-
proaches. For example, some utilities have
focused on cool roof rebates to encourage
consumers to install reflective roofing prod-
ucts. Some local environment departments
have sponsored demonstration projects,
conducted outreach and education efforts
to publicize results, and have provided
grants to support use of mitigation tech-
nologies by residents and industry.
1.1 Demonstration Projects
Local governments, universities, and other
organizations have used projects to demon-
strate a specific heat island mitigation strat-
egy and quantify its benefits in a controlled
environment. Documenting the project
and its results can provide the data and
publicity needed to develop larger initia-
tives, promote new technologies and help
get them to market, and sometimes even
encourage local economic development.
(See the "Stimulating Local Economies and
Businesses" textbox.)
Communities have found heat island dem-
onstration projects to be most effective
when they:
• Target high-visibility projects. Focus-
ing efforts on a prominent building or
site helps attract attention to heat island
mitigation efforts.
• Measure benefits. Highlighting antici-
pated benefits and collecting data on
actual impacts provides useful informa-
tion for planning future activities. These
benefits also illustrate to others the
reasons and means to act.
• Convey lessons learned. Documenting
how demonstration projects are con-
ducted makes them easier to replicate
and improve.
Lead By Example
"Lead by example" programs involve
implementing strategies within lo-
cal and state government facilities,
operations, and fleets, where appro-
priate. These programs offer energy,
environmental, and financial benefits
while creating an important opportu-
nity for governments to demonstrate
the economic feasibility of the strate-
gies they are promoting. This lead-
ership can raise public awareness
of the benefits of urban heat island
reduction strategies, which can lead
to increased public and private sector
support for advancing them.
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REDUCING URBAN HEAT ISLANDS - DRAFT
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A variety of organizations can be the chief
agents of change and the first to test alter-
native technologies, often in highly visible,
public facilities. Demonstration projects
have taken place in parks, schools, and mu-
nicipal buildings like city hall. These proj-
ects often also monitor costs and benefits,
such as energy savings. Examples include:
• Chicago installed a green roof on its
city hall that includes 20,000 plants,
shrubs, grasses, vines, and trees. The
city expects to save directly more than
9,270 kilowatt-hours (kWh) per year of
electricity and nearly 740 million British
thermal units (Btu) per year of natural
gas for heating. This energy savings
translates into about $3,600 annually,
and savings will increase with higher
energy prices. In addition to assess-
ing energy impacts, the green roof has
been designed to test different types of
rooftop garden systems, success rates
of native and non-native vegetation,
and reductions in stormwater runoff.
This city hall green roof has helped to
raise the visibility of green roofs and to
increase public understanding of them.
Chicago's Department of Environment
staff has frequently given presentations
about the roof, which has won numer-
ous awards. For further information, go
to and
look under the Department of Environ-
ment's City Hall green roof project.
• A demonstration project for Tucson
documented how a cool roof re-
duced temperatures inside and on
the roof of the building and saved
more than 400 million Btu annually
in energy. A white elastomeric coating
was installed over a 28,000-square foot
(2,600 m2), unshaded metal roof on
one of the city's administration build-
ings. Following the installation, energy
savings were calculated at 50 to 65
Figure 1: Chicago City Hall Green Roof
Chicago's commitment to green roofs includes
demonstration projects, such as on its City Hall,
education, incentives, and policy actions.
Stimulating Local
Economies and Businesses
The non-profit group Sustainable
South Bronx has developed several
goals for the green roof/cool roof
demonstration project on top of its
office building in Hunts Point. These
goals include gathering research on
local benefits, establishing a resource
for the community, educating New
Yorkers on the value of green roofs,
and advocating sustainable building
practices. The demonstration project
has become a springboard for de-
veloping a local green and cool roof
installation company to provide em-
ployment opportunities in the South
Bronx area. The group's business is
called SmartRoofs and includes a job-
training program for local residents.
See for more information.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
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percent of the building's cooling ener-
gy—an avoided energy cost of nearly
$4,000 annually See for more information.
1.2 Incentives
Incentives have proven to be an effective
way to spur individual heat island reduc-
tion actions. Incentives from governments,
utilities, and other organizations can in-
clude below-market loans, tax breaks,
product rebates, grants, and giveaways. For
example:
• Since 2006, Baltimore County's Grow-
ing Home Campaign has provided
$10 coupons to homeowners toward
the purchase of most trees at local
nurseries. Each coupon represents $5 of
public funds and $5 of retail funds. In
order to validate their coupons, hom-
eowners provide information including
tree type and location planted, which
allows the county to integrate the data
with future tree canopy studies. The
county began the program as an in-
novative way to increase tree canopy
cover as part of its larger "Green Re-
naissance" forest conservation and sus-
tainability plan. In the first two months
of the program, 1,700 trees were plant-
ed. See and
for further information.
• Since 1990, the Sacramento Mu-
nicipal Utility District (SMUD) has
partnered with the Sacramento Tree
Foundation to provide more than
350,000 free shade trees to residents
in the Sacramento area. This program
encourages residents to strategically
plant vegetation around their homes
to reduce energy consumption. Homes
with an eastern, western, or south-
ern exposure that heats up during the
summer are eligible for this program.
SMUD provides trees between four
and seven feet tall (1.2-2.2 m), as well
as stakes, ties, fertilizer, tree delivery,
and expert advice on tree selection
and planting techniques free of charge.
Homeowners must agree to plant and
care for the trees. See for more
information. SMUD also offers rebates
to residential customers who use cool
roofing technologies. The utility offers a
20-cent-per-square-foot (0.09 m2) rebate
to customers who own single-family,
multi-family, or mobile homes with flat
roofs and who install ENERGY STAR®
cool roof products.
• After the success of its green roof dem-
onstration project, Chicago established
green and cool roof grant programs.
The green roof program cites the ability
of green roofs to "create energy savings
for building," "lower surrounding urban
heat temperatures," and "reduce storm
water runoff, improve water quality, and
create conditions for longer-lasting roof
systems." Similarly, the city recognizes
cool roofs "not only help reduce cooling
costs, but can also have a positive envi-
ronmental impact by reducing the urban
heat island effect." In 2005, its first year,
the program supported 20 green roof
installation projects; in 2006, it helped
fund 40. In the fall of 2007, the city an-
nounced that it was expanding the pro-
gram to include cool roofs and expected
to provide about 55 $6,000 grants.
Recipients can use grants for residential,
commercial, or industrial buildings. See
, under
the Department of Environment portion
of the website, for more information.
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REDUCING URBAN HEAT ISLANDS - DRAFT
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• The Pennsylvania Department of
Environmental Protection's Energy
Harvest Program has been providing
grants for specific energy saving proj-
ects since 2003. In 2007, it dispensed
more than $500,000 to green roof
projects across the state. The Energy
Harvest Program overall aims to deploy
innovative technologies and encourages
"proposals that are market-driven, create
jobs, and produce economic develop-
ment within the Commonwealth." See
Energy Harvest Program information
available at: .
• In addition to green roofs, building
owners can also install vertical gar-
dens—sometimes referred to as green
or living walls—on exterior walls to
shade buildings and provide evapo-
transpiration.2 The Houston Down-
town Management District (HDMD)
Vertical Gardens Matching Grant
initiative first gave grants in 2007
to encourage plantings that cover
walls. The grants also support excep-
tional landscaping that adds significant
evapotranspiration and shade for blank
walls, parking garages, and sidewalks.
The program goals include improving
overall aesthetics, pedestrian comfort,
air quality, and reducing the heat island
effect. Grants cannot exceed half of the
total project cost or $20,000, and contri-
butions can be in kind. Tenants, prop-
erty owners, and registered non-profits
can all apply. See .
• Since 2002, Austin Energy has given
10-cent-per-square-foot rebates for
cool roof installations. Customers
must use cool roof products that have
a minimum reflectivity of 75 percent,
and the project must pass a cost-benefit
analysis. The utility has been promoting
cool roof products as a cost-effective
and low-risk approach to reducing
cooling loads and peak demand. As of
2005, Austin Energy had awarded more
than $164,000 as rebates, represent-
ing more than 1.5 million square feet
(140,000 m2) of roof area and saving
an estimated 1.25 million kWh of en-
ergy. See for more information.
Energy Incentives
The Database of State Incentives for
Renewables and Efficiency (DSIRE)
provides current information on
state, local, utility, and select federal
incentives that promote renewable
energy and energy efficiency. Some
of the incentives listed, particularly
those that involve energy efficiency
and green building practices, include
heat island reduction strategies. See
.
1.3 Urban Forestry Programs
Urban forestry or tree planting programs
exist in most large cities and counties in
the United States. These programs gener-
ally have broad goals that emphasize the
multiple benefits trees can provide, includ-
ing helping to cool cities. Most of these
programs unite diverse stakeholders, and
their efforts range from short-term, one-
time projects to long-term community
revitalization. Moreover, many states give
grants to communities and organizations
that promote or maintain urban forests. For
example, Wisconsin will disburse $530,000
in roughly 40 grants in 2008 as part of a
program it has operated since 1993; South
Dakota has run a similar program since
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
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1991 -3,4 As of early 2008, the Washington
State legislature was working on several
bills that would support and expand local
urban forestry efforts in recognition of how
urban trees and vegetation improve air
quality reduce temperatures, enhance qual-
ity of life, and reduce and filter stormwater
runoff.5
Frequently, urban afforestation focuses on
low-income communities, where tree cover
is sparse. For example:
• The Pennsylvania Department of
Conservation and Natural Resources
oversees a project called TreeVitalize,
which brings together county and local
governments, foundations, trade asso-
ciations, and private industry to restore
tree cover in the southeastern part of
the state. TreeVitalize aims to plant
more than 20,000 trees in approximate-
ly 40 neighborhoods in Bucks, Chester,
Delaware, Montgomery, and Philadel-
phia counties. The $8 million program
targets neighborhoods in older cities,
boroughs, and townships in which tree
cover is below 25 percent. See for more information.
• Groundwork Elizabeth, a nonprofit
group in Elizabeth, New Jersey, works
to involve neighborhood residents
in community revitalization projects,
Tree Maintenance and Education
Many urban forestry programs explain that it is easy to plant trees but difficult to
maintain them, particularly until they become well established. In order to ensure
most trees survive, programs have enlisted and empowered volunteers to care for
trees until they are established. Community participation is important because most
urban trees are not under public jurisdiction.
Often tree planting programs train participants in proper tree planting techniques
and care. In Pennsylvania, TreeVitalize provides nine hours of classroom and field
training to community residents who want to become urban forestry leaders. The
classes cover tree identification, planting, pruning, mulching, tree biology/physiol-
ogy, proper species selection, community tree care, and proper pruning. Residents
also can learn how to organize community-assisted tree planting projects. Graduates
are eligible to participate in advanced training and other events.
Other programs require community members to pledge to maintain and protect the
trees that are planted. For example, Los Angeles residents interested in free trees
from the Trees for a Green LA program first participate in an online or neighborhood
workshop. Then, they complete a site plan and apply for their free trees. Residents
pledge on their applications to plant and care for the trees in a proper manner and
allow the city to inspect their work for overall program evaluation and quality assur-
ance. See .
Please see the "Trees and Vegetation" chapter of this compendium for more informa-
tion about urban forestry benefits and implementation considerations.
6
REDUCING URBAN HEAT ISLANDS - DRAFT
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including tree planting at local schools
and parks. The organization was instru-
mental in getting Elizabeth involved in
New Jersey's Cool Cities Initiative, which
aims to plant trees primarily in the large
cities of New Jersey with low tree cover-
age. See for more information.
1.4 Weatherization
Communities have used weatherization
programs as an opportunity to mitigate
heat islands, protect public health, and save
energy. Weatherization usually involves
making the homes of qualifying residents,
generally low-income families, more en-
ergy efficient at no cost to the residents.
States use weatherization funds provided
by the U.S. Department of Energy (DOE)
Weatherization Assistance Program to help
recipients cover heating bills and invest in
energy efficiency actions that lower costs.
States can also use the funds to install cool-
ing efficiency measures, such as screening
and shading devices.
The Energy Coordinating Agency (ECA)
of Philadelphia, which administers the
city's weatherization services, has applied
cool roof coatings as part of its package
of energy efficiency treatments. Through
its Cool Homes Program, more than 550
residences in the Philadelphia area have
had their roofs coated. ECA commissioned
a study that found the cool coatings and
increased insulation eliminated 90 percent
of the heat gain through the ceiling, reduc-
ing top-floor ceiling temperatures by an
average of 4.7°F (2.6°C) and chest-height
temperatures by 2.4°F (1.3°C). These re-
duced temperatures lowered air condition-
ing loads by about one-third in a typical
rowhouse.6 See for
more information.
Heat Health—An
Opportunity to Advance
Heat Island Mitigation
Strategies
Several large cities have developed
programs to minimize health impacts
from excessive heat events. These
efforts provide an opportunity to
educate communities about urban
heat islands and promote heat is-
land reduction strategies, particularly
shade tree planting and cool roof
applications, as a long-term miti-
gation or adaptation strategy. For
example, Philadelphia has long been
concerned with reducing heat-related
mortality. The city was the first in
the United States to implement a
Heat Health Watch-Warning System,
which has become a worldwide
model for heat wave forecasting.
When the Philadelphia Public Health
Department educates citizens about
excessive heat events and immedi-
ate counter-measures, such as using
telephone heat hotlines and taking
advantage of public air-conditioned
buildings, or "cooling centers," it also
provides them information about
longer-term heat island reduction
strategies.
EPA's Excessive Heat Events Guidebook
explains how local public health of-
ficials and others can assess their vul-
nerability and develop and implement
notification and response programs.
See
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1.5 Outreach and Education Programs
Almost all communities have found that
heat island reduction efforts involve some
element of outreach and education. For
example, TreeUtah has launched a com-
prehensive initiative, the MetroGreening
Program, that uses advertising, outreach,
and educational workshops to help pro-
mote proper planting and maintenance of
trees to reduce heating and cooling costs,
diminish the heat island effect, and achieve
other benefits in Utah's most densely-
populated regions. See for more information.
Further, the Utah State Energy Program,
Utah Department of Natural Resources, and
the National Energy Foundation worked
together to create the Utah Kool Kids pro-
gram to teach elementary and secondary
age students about urban heat islands,
their impacts on energy and air qual-
ity, and heat island reduction strategies.
The program gives teachers lesson plans,
overheads, test questions, experiments,
and research tools to engage students. See
for
more information.
Some outreach and education programs
focus specifically on reaching students. The
Cool Schools program in Los Angeles
teaches students to become environ-
mental stewards through hands-on and
classroom experience. Through the proj-
ect, students have helped plant hundreds
of trees around Los Angeles schools. Cool
Schools creates an opportunity to teach
lessons on biology, botany, horticulture,
and related topics. See .
1.6 Awards
Governments, community groups, and
corporations have rewarded exemplary
work as a way to highlight innovation and
promote solutions to mitigate heat islands
across the public and private sectors. Ex-
amples of award programs include:
• Home Depot Foundation's Awards
of Excellence for Community Trees.
Since 2005, this foundation has rec-
ognized public/private collaborations
for their leadership and development
of successful tree planting initiatives.
Winning projects in large and small city
categories receive $75,000 and runners-
up receive $25,000. Though the city and
nonprofit winners are both recognized,
the award money is given to the non-
profit for continued tree planting work.
• Green Roofs for Healthy Cities'
Green Roofs Awards of Excellence.
Since 2003, this nonprofit has recog-
nized a variety of green roof projects
for integrated design and implementa-
tion. The program rewards extensive
and intensive green roof projects, as
well as research teams and citizens who
have advanced the implementation of
green roofs though public policy.
• ENERGY STAR Awards. Since 1993,
EPA has hosted the ENERGY STAR
Awards to recognize outstanding par-
ticipants in the ENERGY STAR Program.
National Coatings Corporation, a manu-
facturer of cool roof materials, was rec-
ognized in 2000. The San Diego Unified
School District (SDUSD) won an award
in 2007 because more than 140 of its
200 buildings met ENERGY STAR crite-
ria. Some of those buildings included
cool roofs combined with photovoltaic
cells that could produce more than 3.5
MW of electricity.7
8
REDUCING URBAN HEAT ISLANDS - DRAFT
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Figure 2: Cool Roofs with Solar Panels
in San Diego
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z>
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• EPA's Regional Office in New Eng-
land's Environmental Merit Award
Program. For more than 30 years, EPA
Region 1 has honored teachers, citizen
activists, business leaders, scientists,
public officials, and others who have
made outstanding contributions to pub-
lic health and the natural environment.
Awards are given across environmental
disciplines and have highlighted heat
island reduction strategies, such as cool
roofs. In 2005, Sarnafil Roofing Sys-
tems, Inc., received a Merit Award for
its highly reflective roofing products.8
2. Policy Efforts
Some local and state governments have
included urban heat island mitigation
strategies in policies or regulations, which
range from purchasing guidelines to build-
ing codes. A number of these actions have
helped remove barriers or provide incen-
tives for implementing mitigation strate-
gies. Others have prescribed minimum
requirements, especially for new construc-
tion. Policy efforts can include:
• Procurement
• Resolutions
• Tree and landscape ordinances
• Comprehensive plans and design
guidelines
• Zoning codes
• Green building standards
• Building codes
• Air quality standards.
2.1 Procurement
Many local governments interested in
mitigating heat islands started by procuring
cool technologies for municipal buildings.
Since state and local governments usually
put construction work and material sup-
plies out for bid, they can revise bid speci-
fications to include cool products.
For example, Tucson, Arizona, requires
that air-conditioned city facilities use
cool roofing materials for most new con-
struction and roof replacements. The city
revised its general bid criteria to ensure
that materials used are equivalent to those
on the ENERGY STAR Roofing Products list.
When a local government requires contrac-
tors to use cool products in this manner, it
becomes easier to encourage additional use
of these products on private projects.
After successfully demonstrating the use
of permeable pavements, Chicago began
a Green Alley initiative that encourages
use of porous paving whenever an alley
needs to be re-paved. Forty-six alleys were
renovated under this initiative in 2007, and
ultimately, almost 2,000 miles of alleyways
will be made permeable. The "Chicago
Green Alley Flandbook" can be found
through the website < http://egov.cityofchi-
cago.org/> under the City Department of
Transportation programs.
The San Diego Unified School District won an
ENERGY STAR award in 2007 because almost 70
percent of its buildings, including this elementary
school with a cool roof and solar panels, met
ENERGY STAR specifications.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
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Figure 3: Permeable Pavement in
Chicago Alley
Raking grave! into a Grave!pave2 system.
Model Resolutions and
Policies
The International Council for Local
Environmental Initiatives (ICLEI),
a nonprofit organization, runs an
Urban Heat Island Initiative program
that provides assistance to local
governments. ICLEI hosts a website
that provides
policy information, such as sample
language for developing a heat island
resolution and a model policy frame-
work.
ICLEI works with local governments
to coordinate workshops throughout
the United States to help understand
heat island impacts and mitigation
strategies. These workshops can
help communities develop a heat
island mitigation project or program.
See for more information.
2.2 Resolutions
A resolution is a document stating a
group's awareness of and interest in an ef-
fort, such as a heat island mitigation proj-
ect. Generally, a city or county council, or
organizations such as air quality boards or
planning commissions, issue resolutions.
A resolution does not necessarily indicate
that a program will be supported financial-
ly, but it can be the first step in getting an
initiative started.
In May 2001, the Austin City Council ad-
opted a heat island mitigation resolution
that committed the city manager to review
recommendations for a variety of activi-
ties to diminish heat islands. In September
of that year, the city council awarded $1
million toward implementing the recom-
mendations, which ranged from developing
a cool roof strategy to increasing enforce-
ment of the city's tree-saving ordinance.
See for more information.
In October 2006, Annapolis, Maryland,
adopted a comprehensive energy ef-
ficiency resolution that included gen-
eral goals and specific long-term targets
for adopting a range of energy efficiency
measures. One recommendation was to
increase tree shading so that the city could
sequester carbon dioxide (C02), reduce the
urban heat island effect, and lower ozone
levels. In 2007, the city adopted a new tree
protection ordinance as one step towards
protecting existing shade trees, discussed
below. See for more information.
2.3 Tree and Landscape Ordinances
Many local governments have enacted
tree and landscape ordinances, which can
ensure public safety, protect trees or views,
and provide shade. Three types of ordi-
nances, in particular, are most useful from
a heat island perspective: tree protection,
street trees, and parking lot shade.
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Tree Protection
Tree protection ordinances prohibit the
removal or pruning of trees without a per-
mit. Often, these ordinances apply only to
native trees or trees with historical signifi-
cance. The effectiveness of this type of pro-
vision depends on enforcement and how
strict the requirements are for granting tree
removal permits.
Some ordinances protect not only trees
but also the ground under the crown area
of a tree to prevent root damage. An ordi-
nance in Atlanta, Georgia, for example,
requires that at least 16 square feet (1.5
m2) of soil around the tree must remain
unpaved and open to the air. Toxic chemi-
cals also must be kept away from the trees.
These ordinances are less common than
those that simply restrict removal.
Another approach, often linked to a local
government's subdivision or development
code, is protecting tree stands during new
construction. In this case, developers are
required to preserve tree stands during site
design and protect them once construction
commences. The ordinances can require
protection based on the percentage of a
site, or a minimum point value, with larger,
mature trees earning more points.
Annapolis, Maryland, explicitly recog-
nized the environmental value of trees
and acted to protect them during con-
struction. The "Tree Protection Ordinance"
requires a survey of trees on a proposed
development site and fences or other
means to mark and protect designated
trees during construction. The ordinance
also prohibits certain activities, such as
trenching or grading, within the dripline
of trees, unless specific precautions are fol-
lowed. More information on this ordinance
is available under §17.09 City Code at
.
Figure 4: Fences Protect a Tree During
Construction
Fences can protect not just a tree's trunk and
branches, but also its root system during
construction.
San Antonio, Texas, requires different
levels of tree protection based on tree
class or location. The ordinance classifies
significant trees, heritage trees, and trees
within the 100-year floodplain. For exam-
ple, heritage trees (defined, for most spe-
cies, as trees 24 inches [60 cm] or greater in
diameter at breast height [DBH]), must be
preserved. The ordinance, however, gener-
ally counts total tree diameter-inches at a
site, not individual trees, and gives flex-
ibility in preservation: up to 90 percent of
the tree-diameter-inches can be considered
preserved if the developer plants an equal
or greater number of tree-diameter-inches
elsewhere. Developers can also fulfill the
preservation requirement by contributing
to the city's tree fund. For details, see the
ordinance and its amendments at chttp://
epay.sanantonio.gov/dsddocumentcentral/
upload/2003%20Tree%20Preservation%20
Ordinance.pdf> and .
Street Trees
Street tree ordinances generally govern
how to plant and remove trees along pub-
lic rights-of-way and land that is privately
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
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owned but accessible by the public. At a
minimum, these ordinances designate the
numbers or types of trees that should be
planted. More effective street tree policies
include guidelines on tree selection, instal-
lation, and maintenance to lengthen a street
tree's life and minimize problems with pave-
ment, electrical wires, and buildings.
For example, Orlando, Florida, specifies
that trees must be planted along both
sides of a street, with one tree every 50 to
100 feet (15-30 m). The selected trees must
eventually be capable of reaching a mini-
mum height of 40 feet (12 m) and a crown
spread of 30 feet (9 m). The ordinance is
available at .
Seattle requires a street use permit be-
fore landscaping in a planting strip in
a public right-of-way. For street trees, the
strip must be at least 5 feet (1.5 m) wide,
unless specific approval from the city's
arborist is received. Five feet is generally
recommended as the minimum width for
planting most trees. A guide is available to
help property owners select and plant trees
in accordance with the city's requirements.
See for further information.
Parking Lot Shade
Some communities require parking lots be
shaded to cool pavement and cars, which
increases comfort, reduces the heat island
effect, and lowers evaporative emissions
from parked cars. For example, since 1983,
an ordinance in Sacramento's zoning
code has required that enough trees be
planted to shade 50 percent of new, or
significantly altered, parking lots after 15
years of tree growth. A 2001 study found
that the lots were only achieving about 25
percent shading because sometimes shade
was double-counted, trees did not grow to
their expected size under the conditions
Figure 5: Parking Lot Shade Guidelines
Shade diagrams, such as this one from Elk Grove,
California, help determine if planned or actual
vegetation meet the communities guidelines.
of the lot, or trees were not adequately
dispersed.^ Thus, Sacramento modified its
code in 2003 to improve coverage.10
Chicago has a landscape ordinance that
requires planting trees or shrubs on
parkways and landscaping parking lots,
loading docks, and other vehicular use
areas, both within the sites themselves and
to screen their perimeter. The ordinance
applies to most new building construc-
tion, as well as to repairs, remodeling, and
enlargements of a particular size and cost.
The Bureau of Forestry, which maintains
the standards, must inspect and approve all
parkway vegetation prior to planting. The
Chicago Department of Zoning reviews all
building and zoning permit applications to
ensure compliance with the ordinance. See
.
In 2007, the city of Baton Rouge strength-
ened its landscape ordinance, which
requires tree planting on all new develop-
ments, excluding single-family residences.
The ordinance requires two shade trees for
every 5,000 square feet (465 m2) of site, and
100%
Notes:
l.This diagram is intended to reflect the manner in which
shade is credited under various conditions.
2.Trees may recfceve 25%, 50%, 75% or 100% as shown.
3. Shade overlap ts not counted twice.
100%
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REDUCING URBAN HEAT ISLANDS - DRAFT
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one shade tree per 600 square feet (55 m2)
of street frontage. Parking lot requirements
include one shade tree per 15 parking spaces
for a lot with one to 25 spaces; one shade
tree per 12 parking spaces for a lot with 25
to 100 spaces; and one shade tree per 10
parking spaces for a lot over 100 spaces. For
example, a 10,000-square-foot (465 m2) site
with 600 square feet (55 m2) of storefront
and 150 parking spaces would require 20
shade trees (i.e., four for the square footage
of the site, one for the store frontage, and 15
for the parking lot). For more information
on Ordinance 12692, see the city's informa-
tion bulletin at .
2.4 Comprehensive Plans and Design
Guidelines
Comprehensive plans and design guide-
lines are another way that communities
have incorporated opportunities to pro-
mote heat island reduction. Comprehensive
plans, sometimes called general plans in
California and other states, are adopted by
a legislative body of a local government,
and set forth policies, goals, and objectives
to direct development and conservation
that occurs within its planning jurisdiction.
They generally have a broad scope and
long-term vision. Design guidelines provide
a connection between general planning
policies and implementing regulations,
such as zoning codes and subdivision regu-
lations. Design guidelines convey a sense
of the preferred quality for a place by be-
ing descriptive and suggestive.
The "Environmental Planning Element"
in the Gilbert, Arizona, general plan lists
mitigating heat islands as a core goal.
Specific policies under the goal include:
1) developing criteria that will identify
projects that might contribute to the heat
island effect and will require an evalua-
tion of mitigation techniques; 2) seeking
sponsors such as educational institutions,
utility companies, and government entities
to promote heat island awareness among
landowners, developers, engineers, and ar-
chitects; and 3) promoting design concepts
using engineered green space to maximize
shading of surfaces that tend to heat up,
promote education and awareness of cool
roof materials and construction techniques,
and promote alternative pavement technol-
ogies in parking areas. For more informa-
tion see .
Design guidelines can take a holistic ap-
proach to heat island mitigation or spe-
cific mitigation strategies. For example,
Toronto's Official Plan includes policies
to reduce the urban heat island and
achieve a wide range of environmen-
tal gains. As part of that plan, the city
released draft parking lot guidelines in
November 2007 that call for shade trees,
permeable and reflective pavements, and
other design features to manage stormwa-
ter, reduce energy consumption, and lower
urban temperatures.11
The town of Highland, Utah, created a mas-
ter plan for a 50-acre (200,000 m2) overlay
zone to be privately developed as a town
Figure 6: Portland Eco-Roof
The Portland Bureau of Environmental Services
(BES) has a green roof on its headquarters. The city
allows denser development for projects that use
green roofs, or eco-roofs as the city calls them.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
13
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center. The city design guidelines for the
zone recommended several heat island miti-
gation elements, including reflective roofing,
reflective parking lot surfaces, and landscap-
ing. Those guidelines were then adopted into
the zoning requirements for the town center.
In contrast, Portland, Oregon, has focused
on the use of eco-roofs in the city center
district, primarily for their aesthetic and
storm water management benefits. Design
guidelines call for integrating vegetated roofs
into central city projects. As discussed in
the next section, Portland has taken specific
steps in its zoning code to achieve this result.
2.5 Zoning Codes
Zoning codes implement the goals and
objectives of a comprehensive plan. These
regulations generally dictate function for an
area, building height and bulk, population
density, and parking requirements. Zoning
codes can also promote heat island mitiga-
tion strategies in various ways. For example,
as noted in Section 2.3, cities such as Sac-
ramento have adopted parking lot shading
requirements as part of their zoning codes.
Communities have also allowed density
bonuses for construction that adopts mitiga-
tion strategies. In 2001, Portland, Oregon,
modified its zoning code to include an
"eco-roof development bonus" for devel-
opers to install rooftop gardens or "eco-
roofs." In Title 33 of the Zoning Code there
is a floor area ratio bonus for projects that
install eco-roofs in Portland's central district.
The bonus amount depends on the extent
of the eco-roof coverage. If the eco-roof cov-
ers 60 percent or more of the roof surface,
developers can build an additional 3 square
feet (0.3 m2) for each square foot of green
roof. If the green roof covers a lower per-
cent of the surface, the bonus is reduced.
See Section 33.510 of the code at for specific information.
Chicago also has a similar provision,
with the floor area ratio density bonus
based on the amount by which a green
roof exceeds 50 percent of the roof surface.
2.6 Green Building Programs and Standards
Green building initiatives place a high pri-
ority on human and environmental health
and resource conservation over the life
cycle of a building. Many local, state, and
federal governments have adopted green
building programs, or standards, that cap-
ture heat island reduction strategies.
For example, local governments such as
Arlington, Virginia, and San Jose, Cali-
fornia,12 are basing their municipal green
building requirements on the U.S. Green
Building Council (USGBC) Leadership in
Energy and Environmental Design (LEED)
Rating System™. Green Globes, operated
by the Green Building Initiative (GBI) in
the United States, is another rating system
that communities are using. The Canadian
government requires all federal buildings to
meet the Canadian version of Green Globes,
Go Green and Go Green Plus. States like
Arkansas and Maryland recognize both
LEED and Green Globes in their green
building initiatives. Under both rating sys-
tems, buildings can earn credits towards
certification by providing shade vegetation,
installing cool or green roofs, and using
highly reflective and emissive pavements or
permeable paving products, all measures that
reduce the heat island effect.
Specific to homes, programs such as Earth-
Craft House, created by the Greater Atlanta
Home Builders Association and Southface
Energy Institute, award points for resi-
dences that preserve and plant trees, install
ENERGY STAR cool roof products, or use
permeable pavement. In addition, EarthCraft
Houses must meet ENERGY STAR certifica-
tion. Communities from Virginia to Florida
have constructed EarthCraft homes.
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REDUCING URBAN HEAT ISLANDS - DRAFT
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Seattle Green Factor
Seattle has adopted minimum landscape requirements, known as the Seattle Green
Factor, for new developments in commercial areas in the city. This program requires
that, as of late January 2007, certain new developments in neighborhood business
districts must provide for vegetative cover on the equivalent of 30 percent of the ap-
plicable property. The regulations apply to developments with more than four dwell-
ing units, more than 4,000 square feet (370 m2) of commercial uses, or more than
20 new parking spaces. Developers can use a menu of strategies, including planting
new trees, preserving trees, and installing green roofs and green walls to meet this
target. The regulations are part of the city's Commercial Code and encourage plant-
ing of layers of vegetation and larger trees in areas visible to the public. The rules
also include bonuses for harvesting rain water and choosing plants that need less
water. The city has developed a worksheet to help applicants calculate a "score" that
indicates whether various mixes of landscaping measures meet the requirements,
which will allow developers to try different combinations of features. See for more information.
Figure 7: Seattle Public Library
Seattle promotes green roofs, such as this one on a city library, through its Green Factor program.
Meanwhile, since 1996, the city's Neighborhood Matching Fund program has provided
more than 17,200 trees to more than 600 neighborhood groups for Seattle's streets
and parks, and the city has established the Emerald City Task Force, which advises the
city on incentives and policies to encourage private property owners—residential and
commercial—to improve their land by preserving existing trees and planting new ones.
See for more information.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
15
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Further, the National Association of
Home Builders is working with the In-
ternational Code Council to develop a
national green building standard for
homes that captures heat island reduction
strategies as well.
Whereas the above efforts allow building
owners to choose technologies and do not
guarantee that heat island reduction strat-
egies will be included in the mix, some
communities, such as Frisco, Texas, have
gone so far as to require cool roofs in
their commercial green building pro-
grams. In late 2006, the Frisco City Coun-
cil approved requirements for most new
commercial construction to install ENERGY
STAR labeled cool roof products.
2.7 Building Codes
Building codes are regulations adopted by
local and state governments that establish
standards for construction, modification,
and repair of buildings and other struc-
tures. An energy code is a portion of the
building code that relates to energy usage
and conservation requirements and stan-
dards (see ). Some
cities and states have begun including cool
roofing in their building codes because of
its potential to save energy, particularly
during peak loads. For example:
• In January 2003, Chicago amended
its energy code to require roof in-
stallations on or prior to December
31, 2008, to meet a minimum solar
reflectance of 25 percent. The amend-
ments apply to most air-conditioned
buildings with low-sloped roofs. After
December 31, 2008, contractors must
use roofing products that meet or ex-
ceed the minimum criteria to qualify
for an ENERGY STAR label.
• Georgia was the first state to add
cool roofs to its energy code, in
1995. Georgia allows a reduced roof
The Foundation for
Including Cool Roofs in
Energy Codes
The American Society of Heating,
Refrigerating, and Air-conditioning
Engineers (ASHRAE) has developed
energy-efficient design standards
that provide minimum requirements
for both commercial and residential
buildings. The ASHRAE standards un-
derlie most state building and energy
codes. ANSI/ASHRAE/IESNA Stan-
dard 90.1-1999, Energy Standards for
Buildings Except Low-Rise Residential
Buildings, and ANSI/ASHRAE Stan-
dard 90.2-2001, Energy-Efficient De-
sign of Low-Rise Residential Buildings,
provide guidelines for new equip-
ment, systems, and buildings. These
standards originally were developed
in response to the 1970s energy crisis
and now include credits pertaining
to cool roofing. For example, Adden-
dum f to 90.2-2001 allows high-albedo
roofs in hot and humid climates as
part of the energy efficiency ceiling
calculation for a residential building.
insulation level if a cool roof with a 75
percent minimum solar reflectance and
75 percent minimum thermal emittance
is installed.13 Note that if building own-
ers install a cool roof and simultane-
ously reduce insulation, there may be
no net energy savings.
• Florida also gives cool roofs credit
in its building energy code. Buildings
using a roof with 70 percent minimum
solar reflectance and 75 percent mini-
mum thermal emittance are eligible
to reduce the amount of insulation
needed to meet building efficiency
standards, as long as a radiant barrier
16
REDUCING URBAN HEAT ISLANDS - DRAFT
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is not also installed in the roof plenum
or attic space.
• In response to electrical power shortag-
es, California added cool roofs as an
energy efficiency option to its build-
ing energy code (Title 24) in 2001. The
code defines a cool roof as having a
minimum solar reflectance of 70 per-
cent and minimum thermal emittance of
75 percent, unless it is concrete or clay
tile, in which case it can have a mini-
mum solar reflectance of 40 percent.
This 40-percent rating incorporates new
cool-colored residential products into
the standard. In 2005, these cool roof
provisions became mandatory require-
ments for all new non-residential con-
struction and re-roofing projects that
involve more than 2,000 square feet
(180 m2) or 50 percent replacement.14
The code allows owners to meet these
requirements in a variety of ways.
- The simplest approach is to apply a
cool roof that meets the minimum
requirements.
- Another alternative is to use roof
products that do not meet the cool
roof criteria and then offset the
reduced performance levels by
implementing other measures, such
as insulation and window improve-
ments, that exceed minimum re-
quirements.
- The third, and most flexible op-
tion, is to use whatever methods are
deemed practicable as long as the
code's specific performance goal is
reached. In this scenario, the build-
ing owner creates a model of all the
characteristics that affect the energy
consumption of the building to
determine the mix of measures that
will meet the code criteria. The Cali-
fornia Energy Commission provides
computer software for this compli-
ance option.
Cool Roofs in California
California has a long history of sup-
porting cool roof research and imple-
mentation to alleviate peak energy
demand. In 2001, the state passed
legislation that activated emergency
measures, including cool roofs, to
reduce peak demand and mitigate
the energy crisis. The cool roofs pro-
gram was subsequently formalized
as the Cool Savings Program, which
provided rebates to building owners
for installing roofing materials with
high solar reflectance and thermal
emittance. The highest rebate went
to roofs on air conditioned buildings,
while buildings with rooftop ducts
and other non-residential buildings
were eligible for a slightly lower
rebate. The program was adminis-
tered by the California Energy Com-
mission but implemented by five
organizations directly responsible for
promoting the program, recruiting
customers, verifying project comple-
tion, and paying incentives of 15 to
25 cents per square foot (0.09 m2) of
eligible roofing area. The program
was so successful that California re-
vised Title 24 to make cool roofs on
certain new or renovated buildings
mandatory starting in 2005.
California began the process of updat-
ing Title 24 in late 2005, with final revised
standards due in 2008. As part of this
update, California is investigating extend-
ing cool roof requirements to houses and
buildings with steep-sloped roofs. See
and for
further information.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
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2.8 Air Quality Requirements
As summertime temperatures rise, the rate
of ground-level ozone formation, or smog,
increases. By lowering temperatures, urban
heat island mitigation strategies can help
reduce ground-level ozone concentrations.
Many cities and counties are struggling to
attain national ambient air quality stan-
dards (NAAQS), particularly for ground-
level ozone. Most of these areas have
adopted a wide range of emission con-
trol strategies on traditional air pollution
sources and are seeking innovative ways to
further reduce air pollution levels. Commu-
nities are considering urban forestry and
cool roofs, in particular, as technologies
that can help them reach attainment.
Under the Clean Air Act, State Implemen-
tation Plans (SIPs) are federally approved
and enforceable plans that identify how
each state will meet and maintain federal
air quality standards. EPA has developed
three policies that help states to include
heat island reduction strategies in their
SIPs. See the "Policies to Advance Heat
Island Mitigation in SIPs" textbox.
A few areas have been working to include
heat island reduction strategies in their SIPs,
including Atlanta, Houston, Sacramento, and
the Washington D.C. metropolitan area. In
2006, Sacramento secured a large Conges-
tion Mitigation and Air Quality (CMAQ)
Improvement Program grant to work on
including urban forestry in its SIR The
project, known as the Urban Forests for Clean
Air demonstration project, involves the Sac-
ramento Tree Foundation, the USDA For-
est Service, the Sacramento Area Council of
Governments, and the Sacramento, El Dorado,
Placer, and Feather River Air Districts. The
project includes three phases: 1) initial esti-
mates of the effects of the urban forest on air
quality; 2) development of improved mod-
els to analyze these impacts; and 3) a final
report on the findings. Under the first phase,
Heat Island Mitigation
Strategies Reduce Ground-
Level Ozone
Ground-level ozone forms more
readily when air temperatures rise.
Strategies to mitigate the urban heat
island reduce air temperatures and
therefore decrease concentrations of
ground-level ozone. These strate-
gies also reduce energy demand for
cooling, which reduces air pollution
and greenhouse gas emissions associ-
ated with energy production. When
selecting vegetation for a green roof
or to plant along a street or other
areas, communities in areas with
poor air quality may want to consider
the volatile organic compound (YOC)
emissions from certain plants, be-
cause YOCs are a pre-cursor chemi-
cal for ground-level ozone. With the
right choice of species, the benefits
of additional trees and vegetation far
outweigh the costs.
the Forest Service's Center for Urban Forest
Research estimated the impacts of trees on
air quality using existing models and statisti-
cal analyses. That analysis predicted that one
million additional trees could lower emissions
of NOx by almost a quarter ton per day and
particulate matter by over one ton per day. If
trees that emitted low levels of volatile organic
compounds (YOCs) were chosen, ground-level
ozone could also be reduced by 1.5 tons daily.
The long-term goal for the project is to devel-
op the technical support for a SIP revision that
includes large-scale, urban tree planting as a
ground-level ozone reduction control strat-
egy for the Sacramento region. See and
for more information.
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REDUCING URBAN HEAT ISLANDS - DRAFT
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Policies to Advance Heat Island Mitigation in SIPs
Currently, three EPA policies help states to include heat island reduction strategies in
their SIPs:
1. The Emerging and Voluntary Measures Policy provides flexibility for states to include
in their SIP nontraditional measures, which are measures that do not directly reduce
emissions at their source such as a scrubber on a utility smokestack. Heat island re-
duction strategies can be included under this policy.
2. The Guidance on State Implementation Plan (SIP) Credits for Emissions Reductions
from Electric-Sector Energy Efficiency or Renewable Energy Measures provides state
and local air quality officials with information on how to incorporate energy efficiency
and renewable energy measures into their SIPs. It includes a step-by-step procedure
for estimating emission reductions from these measures, a list of tools and resources
for more information, and examples of proposed SIP submissions. This policy en-
courages cool roofs particularly. See .
3. The Bundled Measures Policy allows a state to combine many projects and programs
that individually would not result in large reductions of air pollution emissions. EPA
considers the performance of the entire bundle (the sum of the emissions reductions
from all the measures in the bundle) for SIP evaluation purposes, not the effectiveness
of any single measure. In this way, the responsible agency can include innovative
strategies, such as heat island mitigation measures, that may otherwise be overlooked
because they do not on an individual basis provide significant air quality benefits.
The Washington D.C. region's SIP in-
cludes a Regional Canopy Management
Plan as a ground-level ozone reduction
strategy. The plan involves working with
local governments to establish goals for in-
creasing tree canopy coverage and decreas-
ing ground-level ozone pollution. In June
2007, Fairfax County, Virginia, set a prece-
dent by selecting an urban forestry canopy
goal of 45 percent. The county developed
this target after it determined that current
tree management efforts would lead to a
decrease in canopy size from 41 percent
to 37 percent over the next 30 years. To
combat this loss, the county has proposed
increasing the average number of trees
planted from 21,000 to 84,000, justifying
the expense of additional trees by citing
the multiple benefits they provide.
Figure 8:Tree Canopy in Washington D.C.
Construction in and around Washington, D.C., has
reduced tree cover (green in this image), but many
efforts have formed to slow or reverse this trend.
HEAT ISLAND REDUCTION ACTIVITIES - DRAFT
19
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Endnotes
1 Examples of sustainable or low-impact development (LID) initiatives are The Sustainable Sites
Initiative (), a collaboration between the American Society of Land-
scape Architects, the Lady Bird Johnson Wildflower Center, the US Botanic Garden, and other
groups; and EPA's Low Impact Development Page () and Green
Infrastructure Action Strategy ().
2 Bass, B. and B. Baskaran. 2003. Evaluating Rooftop and Vertical Gardens as an Adaptation
Strategy for Urban Areas. Report No. NRCC-46737. National Research Council Canada. Toron-
to, Canada.
3 The Wisconsin Office of the Governor. 2008. Governor Doyle Announces $500,000 in Urban
Forestry Grants. 17 January. Retrieved 18 January 2008 from .
4 South Dakota Department of Agriculture. 2008. Urban & Community Forestry Comprehensive
Challenge Sub-grant. Retrieved 18 January 2008 from .
6 Blasnik, M. 2004. Impact Evaluation of the Energy Coordinating Agency of Philadelphia's Cool
Homes Pilot Project. M. Blasnik & Associates. Boston, MA.
7 EPA. 2007. 2007 ENERGY STAR Awards. Retrieved 30 December 2007 from .
8 EPA. 2007. 2005 Environmental Merit Award Recipients. Retrieved 15 December 2007 from
.
9 McPherson, E. G. 2001. Sacramento's parking lot shading ordinance: environmental and eco-
nomic costs of compliance. Landscape and Urban Planning. 57:105-123.
10 City of Sacramento. Tree shading requirements for parking lots. §17.68.040 City Code. Re-
trieved 29 November 2007 from .
11 City of Toronto. 2007. Design Guidelines for "Greening" Surface Parking Lots. Retrieved 29
November 2007 from .
12 For further information about Arlington's and San Jose's codes, respectively, see and under Green Building.
13 U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. 2008. Georgia
Energy Code 1995. Retrieved 11 February 2008 from .
14 Levinson, R., H. Akbari, S. Konopacki, and S. Bretz. 2002. Inclusion of Cool Roofs in Nonresi-
dential Title 24 Prescriptive Requirements. Paper LBNL-50451. Lawrence Berkeley National
Laboratory, Berkeley, CA.
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