Both types of green roofs can be used on residences, industrial facilities,

offices, and other commercial property. Green roofs are widespread in

Europe and Asia, and are becoming more common in the United States. 

Cool Pavement

Pavements with low

solar reflectance absorb

large amounts of heat and

can be up to 70 ̊ F (40 ̊ C)

hotter in the sun than

cooler alternatives. 

Portland cement

concrete and asphalt

concrete – commonly

called “concrete” and

“asphalt,” respectively –

are the most common

paving materials for sidewalks and streets. Most new concrete has a

solar reflectance, or albedo, of 35-40 percent; the solar reflectance of

fresh asphalt is typically 5-10 percent. 

Over time, the albedo of these pavements change. Concrete darkens

from the build-up of tire residue, dirt, and oil, and asphalt lightens as the

asphalt binder wears away to expose the underlying rock aggregate.

To maximize the albedo of both types of pavement, lighter-colored

aggregate can be used in the pavement mix. Alternatively, asphalt

pavements can be covered with high-albedo sealcoats, small rocks 

set in binder, or a thin layer of concrete. For concrete applications,

using lighter-colored sand and cement can increase reflectivity.

Permeable, or porous, pavements allow water to percolate and evaporate,

cooling the pavement surface and surrounding air. Permeable pavements

can be constructed from a number of materials including concrete,

asphalt, and plastic lattice structures filled with soil, gravel, and grass. 

Although there is no official standard or labeling program to designate

cool paving materials, communities interested in reducing the heat

island effect may consider surface reflectivity and permeability – along

with other costs and benefits – when selecting a paving product.

What is EPA Doing to Reduce 

Heat Islands? 

Through its Heat Island Reduction Initiative (HIRI), EPA works with

community groups, public officials, industry representatives, researchers,

and other stakeholders to identify opportunities to implement heat

island reduction strategies and evaluate their impacts on energy

demand, local meteorology, air quality, health, and other factors. 

For More Information

EPA’s Heat Island Reduction Initiative 

www.epa.gov/heatisland

EPA Global Warming Information 

www.epa.gov/globalwarming

ENERGY STAR Qualified Cool Roof Products

www.energystar.gov/products

The Lawrence Berkeley National Laboratory's 

Heat Island Group 

http://heatisland.lbl.gov

International Council for Local Environmental Initiatives’ 

Hot Cities Information

www.hotcities.org

NASA’s Global Hydrology and Climate Center (GHCC)

www.ghcc.msfc.nasa.gov

Cool Roof Rating Council

www.coolroofs.org

USDA Urban and Community Forestry Program 

www.fs.fed.us/ucf

Green Roofs for Healthy Cities

www.greenroofs.ca/grhcc

U.S. Green Building Council

www.usgbc.org

Center for Green Roof Research

http://hortweb.cas.psu.edu/research/greenroofcenter 

High-albedo pervious pavement supports light

traffic while mitigating the heat island effect

and allowing stormwater to pass through.

The Difference between Heat Islands and 

Global Warming 

Heat islands describe local-scale temperature 

differences between urban and rural areas. In contrast, global

warming refers to the gradual rise of worldwide average

surface temperatures. 

The village of Fair Oaks in Sacramento, California installed a permeable portland cement concrete 

parking lot at a local park. It avoids the cost of a stormwater drainage system and helps reduce the heat

island effect. 

Cool Pavement in Action
The Energy Coordinating Agency (ECA) in Philadelphia initiated the Cool Homes Program to help elderly residents

escape extreme summertime heat. ECA installs cool roofs and uses other measures to reduce indoor temperatures to

promote comfort and minimize health risks. As of April 2003, the Cool Homes Program had installed over 450 roofs.

Cool Roofs in Action 

For millions of Americans living in and around cities, elevated summertime temperatures are of growing concern.

Commonly referred to as urban heat islands, this phenomenon can impact communities by increasing peak energy demand, 

air conditioning costs, air pollution levels, and heat-related illness and mortality.

Fortunately, there are common-sense measures that communities can take to reduce the negative effects of heat islands. 

What Is a Heat Island?

Heat islands are characterized by urban air and surface temperatures

that are higher than nearby rural areas. Many U.S. cities and suburbs

have air temperatures up to 10 ̊ F (5.6 ̊ C) warmer than surrounding

natural land cover. 

The heat island sketch below shows a city's heat island profile. It

demonstrates how temperatures typically rise from the urban-rural

border, and that the warmest temperatures are in dense downtown areas. 

What Causes Heat Islands?

Heat islands form as cities replace natural land cover with pavement,

buildings, and other infrastructure. These changes contribute to

higher urban temperatures in the following ways:

• Displacing trees and vegetation minimizes the natural cooling

effects of shading and evaporation of water from soil and leaves

(evapotranspiration).

• Tall buildings and narrow streets can heat air that is trapped

between them and reduce wind flow. 

• Waste heat from vehicles, factories, and air conditioners may 

add warmth to the air, further increasing temperatures.

Heat islands are also influenced by a city’s geography and prevailing

weather conditions. For example, strong winds and rain can flush out

hot, stagnant air from city centers, while sunny, windless conditions

can exacerbate heat islands.

When Do Heat Islands Form? 

Heat islands can occur year-round during the day or night. Urbanrural temperature differences are often largest during calm, clear

evenings. This is because rural areas cool off faster at night than

cities, which retain much of the heat stored in roads, buildings, and

other structures. 

How Do Heat Islands Affect Us? 

Increased urban temperatures can affect public health, the environment,

and the amount of energy that consumers use for summertime cooling. 

Public Health: Heat islands can amplify extreme hot weather events,

which can cause heat stroke and may lead to physiological disruption,

organ damage, and even death – especially in vulnerable populations

such as the elderly. 

The Environment: Summertime

heat islands increase energy

demand for air conditioning, raising

power plant emissions of harmful

pollutants. Higher temperatures

also accelerate the chemical

reaction that produces groundlevel ozone, or smog. This threatens

public health, the environment,

and, for some communities, may

have implications for federal air

quality goals.

Energy Use: Because homes and

buildings absorb the sun’s energy,

heat islands can increase the

demand for summertime cooling,

raising energy expenditures. For

every 1° F (0.6° C) increase in

summertime temperature, peak utility loads in medium and large cities

increase by an estimated 1.5 – 2.0 percent. 

Cities in cold climates may actually benefit from the wintertime warming

effect of heat islands. Warmer temperatures can reduce heating

energy needs and may help melt ice and snow on roads. 

In the summertime, however, the same city may experience the

negative effects of heat islands.

 ̊F  ̊C

92

91

90

89

88

87

86

85

33

32

31

30

Rural

Temperature

Urban Heat Island Profile

Commercial

Downtown

Suburban 

Residential Suburban 

Residential

Urban 

Residential

Park

Heat islands are often largest over dense development but may be broken

up by vegetated sections within an urban area.

Heat from City Surface

Volatile 

Organic

Compounds

Nitrogen

Oxides Sunlight Ozone (03) T + +

Ozone forms when precursor compounds 

react in the presence of sunlight and 

high temperatures.
Both types of green roofs can be used on residences, industrial facilities, 

Europe and Asia, and are becoming more common in the United States. 

Cool Pavement 

Pavements with low 

solar reflectance absorb 

large amounts of heat and 

can be up to 70 ̊ F (40 ̊ C) 

hotter in the sun than 

cooler alternatives. 

Portland cement 

concrete – commonly 

called “concrete” and 

“asphalt,” respectively – 

are the most common 

paving materials for sidewalks and streets. Most new concrete has a 

solar reflectance, or albedo, of 35-40 percent; the solar reflectance of 

fresh asphalt is typically 5-10 percent. 

Over time, the albedo of these pavements change. Concrete darkens 

from the build-up of tire residue, dirt, and oil, and asphalt lightens as the 

asphalt binder wears away to expose the underlying rock aggregate. 

pavements can be covered with high-albedo sealcoats, small rocks 

Permeable, or porous, pavements allow water to percolate and evaporate, 

asphalt, and plastic lattice structures filled with soil, gravel, and grass. 

Although there is no official standard or labeling program to designate 

cool paving materials, communities interested in reducing the heat 

island effect may consider surface reflectivity and permeability – along 

with other costs and benefits – when selecting a paving product. 

Heat Islands? 

community groups, public officials, industry representatives, researchers, 

and other stakeholders to identify opportunities to implement heat 

island reduction strategies and evaluate their impacts on energy 

For More Information 

The Lawrence Berkeley National Laboratory's 

Heat Island Group 

http://heatisland.lbl.gov 

International Council for Local Environmental Initiatives’ 

Hot Cities Information 

Cool Roof Rating Council 

USDA Urban and Community Forestry Program 

Green Roofs for Healthy Cities 

U.S. Green Building Council 

Center for Green Roof Research 

http://hortweb.cas.psu.edu/research/greenroofcenter 

High-albedo pervious pavement supports light 

traffic while mitigating the heat island effect 

and allowing stormwater to pass through. 

The Difference between Heat Islands and 

Heat islands describe local-scale temperature 

differences between urban and rural areas. In contrast, global 

warming refers to the gradual rise of worldwide average 

surface temperatures. 

The village of Fair Oaks in Sacramento, California installed a permeable portland cement concrete 

parking lot at a local park. It avoids the cost of a stormwater drainage system and helps reduce the heat 

island effect. 

Cool Pavement in Action 

offices, and other commercial property. Green roofs are widespread in 

concrete and asphalt 

To maximize the albedo of both types of pavement, lighter-colored 

aggregate can be used in the pavement mix. Alternatively, asphalt 

set in binder, or a thin layer of concrete. For concrete applications, 

using lighter-colored sand and cement can increase reflectivity. 

cooling the pavement surface and surrounding air. Permeable pavements 

can be constructed from a number of materials including concrete, 

What is EPA Doing to Reduce 

Through its Heat Island Reduction Initiative (HIRI), EPA works with 

demand, local meteorology, air quality, health, and other factors. 

EPA’s Heat Island Reduction Initiative 

www.epa.gov/heatisland 

EPA Global Warming Information 

www.epa.gov/globalwarming 

ENERGY STAR Qualified Cool Roof Products 

www.energystar.gov/products 

www.hotcities.org 

NASA’s Global Hydrology and Climate Center (GHCC) 

www.ghcc.msfc.nasa.gov 

www.coolroofs.org 

www.fs.fed.us/ucf 

www.greenroofs.ca/grhcc 

www.usgbc.org 

Global Warming 
The Energy Coordinating Agency (ECA) in Philadelphia initiated the Cool Homes Program to help elderly residents

escape extreme summertime heat. ECA installs cool roofs and uses other measures to reduce indoor temperatures to

promote comfort and minimize health risks. As of April 2003, the Cool Homes Program had installed over 450 roofs.

Cool Roofs in Action 

For millions of Americans living in and around cities, elevated summertime temperatures are of growing concern.

Commonly referred to as urban heat islands, this phenomenon can impact communities by increasing peak energy demand, 

air conditioning costs, air pollution levels, and heat-related illness and mortality.

Fortunately, there are common-sense measures that communities can take to reduce the negative effects of heat islands. 

What Is a Heat Island?

Heat islands are characterized by urban air and surface temperatures

that are higher than nearby rural areas. Many U.S. cities and suburbs

have air temperatures up to 10 ̊ F (5.6 ̊ C) warmer than surrounding

natural land cover. 

The heat island sketch below shows a city's heat island profile. It

demonstrates how temperatures typically rise from the urban-rural

border, and that the warmest temperatures are in dense downtown areas. 

What Causes Heat Islands?

Heat islands form as cities replace natural land cover with pavement,

buildings, and other infrastructure. These changes contribute to

higher urban temperatures in the following ways:

• Displacing trees and vegetation minimizes the natural cooling

effects of shading and evaporation of water from soil and leaves

(evapotranspiration).

• Tall buildings and narrow streets can heat air that is trapped

between them and reduce wind flow. 

• Waste heat from vehicles, factories, and air conditioners may 

add warmth to the air, further increasing temperatures.

Heat islands are also influenced by a city’s geography and prevailing

weather conditions. For example, strong winds and rain can flush out

hot, stagnant air from city centers, while sunny, windless conditions

can exacerbate heat islands.

When Do Heat Islands Form? 

Heat islands can occur year-round during the day or night. Urbanrural temperature differences are often largest during calm, clear

evenings. This is because rural areas cool off faster at night than

cities, which retain much of the heat stored in roads, buildings, and

other structures. 

How Do Heat Islands Affect Us? 

Increased urban temperatures can affect public health, the environment,

and the amount of energy that consumers use for summertime cooling. 

Public Health: Heat islands can amplify extreme hot weather events,

which can cause heat stroke and may lead to physiological disruption,

organ damage, and even death – especially in vulnerable populations

such as the elderly. 

The Environment: Summertime

heat islands increase energy

demand for air conditioning, raising

power plant emissions of harmful

pollutants. Higher temperatures

also accelerate the chemical

reaction that produces groundlevel ozone, or smog. This threatens

public health, the environment,

and, for some communities, may

have implications for federal air

quality goals.

Energy Use: Because homes and

buildings absorb the sun’s energy,

heat islands can increase the

demand for summertime cooling,

raising energy expenditures. For

every 1° F (0.6° C) increase in

summertime temperature, peak utility loads in medium and large cities

increase by an estimated 1.5 – 2.0 percent. 

Cities in cold climates may actually benefit from the wintertime warming

effect of heat islands. Warmer temperatures can reduce heating

energy needs and may help melt ice and snow on roads. 

In the summertime, however, the same city may experience the

negative effects of heat islands.

 ̊F  ̊C

92

91

90

89

88

87

86

85

33

32

31

30

Rural

Temperature

Urban Heat Island Profile

Commercial

Downtown

Suburban 

Residential Suburban 

Residential

Urban 

Residential

Park

Heat islands are often largest over dense development but may be broken

up by vegetated sections within an urban area.

Heat from City Surface

Volatile 

Organic

Compounds

Nitrogen

Oxides Sunlight Ozone (03) T + +

Ozone forms when precursor compounds 

react in the presence of sunlight and 

high temperatures.
The Energy Coordinating Agency (ECA) in Philadelphia initiated the Cool Homes Program to help elderly residents

escape extreme summertime heat. ECA installs cool roofs and uses other measures to reduce indoor temperatures to

promote comfort and minimize health risks. As of April 2003, the Cool Homes Program had installed over 450 roofs.

Cool Roofs in Action 

For millions of Americans living in and around cities, elevated summertime temperatures are of growing concern.

Commonly referred to as urban heat islands, this phenomenon can impact communities by increasing peak energy demand, 

air conditioning costs, air pollution levels, and heat-related illness and mortality.

Fortunately, there are common-sense measures that communities can take to reduce the negative effects of heat islands. 

What Is a Heat Island?

Heat islands are characterized by urban air and surface temperatures

that are higher than nearby rural areas. Many U.S. cities and suburbs

have air temperatures up to 10 ̊ F (5.6 ̊ C) warmer than surrounding

natural land cover. 

The heat island sketch below shows a city's heat island profile. It

demonstrates how temperatures typically rise from the urban-rural

border, and that the warmest temperatures are in dense downtown areas. 

What Causes Heat Islands?

Heat islands form as cities replace natural land cover with pavement,

buildings, and other infrastructure. These changes contribute to

higher urban temperatures in the following ways:

• Displacing trees and vegetation minimizes the natural cooling

effects of shading and evaporation of water from soil and leaves

(evapotranspiration).

• Tall buildings and narrow streets can heat air that is trapped

between them and reduce wind flow. 

• Waste heat from vehicles, factories, and air conditioners may 

add warmth to the air, further increasing temperatures.

Heat islands are also influenced by a city’s geography and prevailing

weather conditions. For example, strong winds and rain can flush out

hot, stagnant air from city centers, while sunny, windless conditions

can exacerbate heat islands.

When Do Heat Islands Form? 

Heat islands can occur year-round during the day or night. Urbanrural temperature differences are often largest during calm, clear

evenings. This is because rural areas cool off faster at night than

cities, which retain much of the heat stored in roads, buildings, and

other structures. 

How Do Heat Islands Affect Us? 

Increased urban temperatures can affect public health, the environment,

and the amount of energy that consumers use for summertime cooling. 

Public Health: Heat islands can amplify extreme hot weather events,

which can cause heat stroke and may lead to physiological disruption,

organ damage, and even death – especially in vulnerable populations

such as the elderly. 

The Environment: Summertime

heat islands increase energy

demand for air conditioning, raising

power plant emissions of harmful

pollutants. Higher temperatures

also accelerate the chemical

reaction that produces groundlevel ozone, or smog. This threatens

public health, the environment,

and, for some communities, may

have implications for federal air

quality goals.

Energy Use: Because homes and

buildings absorb the sun’s energy,

heat islands can increase the

demand for summertime cooling,

raising energy expenditures. For

every 1° F (0.6° C) increase in

summertime temperature, peak utility loads in medium and large cities

increase by an estimated 1.5 – 2.0 percent. 

Cities in cold climates may actually benefit from the wintertime warming

effect of heat islands. Warmer temperatures can reduce heating

energy needs and may help melt ice and snow on roads. 

In the summertime, however, the same city may experience the

negative effects of heat islands.

 ̊F  ̊C

92

91

90

89

88

87

86

85

33

32

31

30

Rural

Temperature

Urban Heat Island Profile

Commercial

Downtown

Suburban 

Residential Suburban 

Residential

Urban 

Residential

Park

Heat islands are often largest over dense development but may be broken

up by vegetated sections within an urban area.

Heat from City Surface

Volatile 

Organic

Compounds

Nitrogen

Oxides Sunlight Ozone (03) T + +

Ozone forms when precursor compounds 

react in the presence of sunlight and 

high temperatures.
Both types of green roofs can be used on residences, industrial facilities,

offices, and other commercial property. Green roofs are widespread in

Europe and Asia, and are becoming more common in the United States. 

Cool Pavement

Pavements with low

solar reflectance absorb

large amounts of heat and

can be up to 70 ̊ F (40 ̊ C)

hotter in the sun than

cooler alternatives. 

Portland cement

concrete and asphalt

concrete – commonly

called “concrete” and

“asphalt,” respectively –

are the most common

paving materials for sidewalks and streets. Most new concrete has a

solar reflectance, or albedo, of 35-40 percent; the solar reflectance of

fresh asphalt is typically 5-10 percent. 

Over time, the albedo of these pavements change. Concrete darkens

from the build-up of tire residue, dirt, and oil, and asphalt lightens as the

asphalt binder wears away to expose the underlying rock aggregate.

To maximize the albedo of both types of pavement, lighter-colored

aggregate can be used in the pavement mix. Alternatively, asphalt

pavements can be covered with high-albedo sealcoats, small rocks 

set in binder, or a thin layer of concrete. For concrete applications,

using lighter-colored sand and cement can increase reflectivity.

Permeable, or porous, pavements allow water to percolate and evaporate,

cooling the pavement surface and surrounding air. Permeable pavements

can be constructed from a number of materials including concrete,

asphalt, and plastic lattice structures filled with soil, gravel, and grass. 

Although there is no official standard or labeling program to designate

cool paving materials, communities interested in reducing the heat

island effect may consider surface reflectivity and permeability – along

with other costs and benefits – when selecting a paving product.

What is EPA Doing to Reduce 

Heat Islands? 

Through its Heat Island Reduction Initiative (HIRI), EPA works with

community groups, public officials, industry representatives, researchers,

and other stakeholders to identify opportunities to implement heat

island reduction strategies and evaluate their impacts on energy

demand, local meteorology, air quality, health, and other factors. 

For More Information

EPA’s Heat Island Reduction Initiative 

www.epa.gov/heatisland

EPA Global Warming Information 

www.epa.gov/globalwarming

ENERGY STAR Qualified Cool Roof Products

www.energystar.gov/products

The Lawrence Berkeley National Laboratory's 

Heat Island Group 

http://heatisland.lbl.gov

International Council for Local Environmental Initiatives’ 

Hot Cities Information

www.hotcities.org

NASA’s Global Hydrology and Climate Center (GHCC)

www.ghcc.msfc.nasa.gov

Cool Roof Rating Council

www.coolroofs.org

USDA Urban and Community Forestry Program 

www.fs.fed.us/ucf

Green Roofs for Healthy Cities

www.greenroofs.ca/grhcc

U.S. Green Building Council

www.usgbc.org

Center for Green Roof Research

http://hortweb.cas.psu.edu/research/greenroofcenter 

High-albedo pervious pavement supports light

traffic while mitigating the heat island effect

and allowing stormwater to pass through.

The Difference between Heat Islands and 

Global Warming 

Heat islands describe local-scale temperature 

differences between urban and rural areas. In contrast, global

warming refers to the gradual rise of worldwide average

surface temperatures. 

The village of Fair Oaks in Sacramento, California installed a permeable portland cement concrete 

parking lot at a local park. It avoids the cost of a stormwater drainage system and helps reduce the heat

island effect. 

Cool Pavement in Action