Reducing Urban Heat Islands: Cool Roofs

8/9/2019 Reducing Urban Heat Islands: Cool Roofs

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Reducing Urban Heat IslandsCompendium of Strategies

Cool Roofs


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Acknowledgements

Reducing Urban Heat Islands: Compendium o Strategiesdescribes the

causes and impacts o summertime urban heat islands and promotes

strategies or lowering temperatures in U.S. communities. This compendium

was developed by the Climate Protection Partnership Division in the U.S.

Environmental Protection Agencys Oce o Atmospheric Programs. Eva

Wong managed its overall development. Kathleen Hogan, Julie Rosenberg,

and Andrea Denny provided editorial support. Numerous EPA sta in

oces throughout the Agency contributed content and provided reviews.

Subject area experts rom other organizations around the United States and

Canada also committed their time to provide technical eedback.

Under contracts 68-W-02-029 and EP-C-06-003, Perrin Quarles Associates,

Inc. provided technical and administrative support or the entire

compendium, and Eastern Research Group, Inc. provided graphics and

production services.

PositvEnergy provided support in preparing the Trees and Vegetation, Cool

Roos, and UHI Activities chapters under contract PO #2W-0361-SATX.

Experts who helped shape this chapter include:

Gregory Chin, Andre Desjarlais, Maury Estes, David Hitchcock, Megan

Lewis, Danny Parker, Joyce Rosenthal, Lorraine Ross, Steve Ryan, Rachel

Schmeltz, Peter Turnbull, and Barry Zalph.


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Contents

Cool Roos 1

1. How It Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

1.1 Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

1.2 Solar Reectance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 Thermal Emittance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.4 Temperature Eects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2. Cool Roo Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Low-Sloped Cool Roos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

2.2 Steep-Sloped Cool Roos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

3. Benets and Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.1 Benets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2 Potential Adverse Impacts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

3.3 Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

3.4 Benet-Cost Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4. Other Factors to Consider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.1 Product Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

4.2 Product Labeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

4.3 Installation and Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

4.4 Cool Roong and Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

5. Cool Roo Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

6. Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

6.1 Cool Roo Energy Savings Calculators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

6.2 Roong Programs and Organizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Endnotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26


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Cool Roofs

Cool roong can help address the

problem o heat islands, which re

sults in part rom the combined heat

o numerous individual hot roos in a city

or suburb. Cool roong products are made

o highly refective and emissive materials

that can remain approximately 50 to 60F

(28-33C) cooler than traditional materials

during peak summer weather. Building owners and roong contractors have used these

types o cool roong products or more than

20 years. Traditional roos in the United

States, in contrast, can reach summer peak

temperatures o 150 to 185F (66-85C),2

thus creating a series o hot suraces as well

as warmer air temperatures nearby.

This chapter provides detailed inormation

that mitigation program organizers can use

to understand, plan, and implement coolroong projects and programs. The chapter

discusses:

Key cool roo properties and how theyhelp to mitigate urban heat

Types o cool roong Specic benets and costs o cool roong Measurement and certication o cool

roo products

Installation and maintenance o cool roos

Tools and resources to urther explorethis technology.

Opportunities to Expand Use of Cool

Roofs in Urban Areas

Most U.S. cities have signicant opportunities to

increase the use o cool roos. As part o the U.S.

Environmental Protection Agencys (EPAs) Urban

Heat Island Pilot Project, the Lawrence BerkeleyNational Laboratory conducted a series o analyses

to estimate baseline land use and tree cover inor

mation or the pilot program cities.1

Figure 1 shows the percent o roo cover in our o

these urban areas. The data are rom 1998 through

2002. With roos accounting or 20 to 25 percent o

land cover, there is a large opportunity to use cool

roos or heat island mitigation.

Figure 1: Roo Cover Statistics or Four U.S. Cities(Below Tree Canopy)

Salt Lake City

Sacramento

Houston

Chicago

Percent Coverage

0 5 10 15 20 25

COOL ROOFS DRAFTCOOL ROOFS DRAFT 11


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Wavelength (nanometers)

1 How It Works

Figure 2: Solar Energy versus Wavelength Reaching Earths Surace

1.000.90

ultraviolet visible infrared0.800.700.600.500.400.300.200.100.00

Norma

lizedSolarIntensity

0 200 400 600 800 100012001400160018002000220024002600

Understanding how cool roong works

requires knowing how solar energy heats

roong materials and how the proper

ties o roong materials can contribute

to warming. This section explains solarenergy, the properties o solar refectance

and thermal emittance, and the combined

temperature eect o these two properties

working together.

1.1 Solar Energy

Figure 2 shows the typical solar energy that

reaches the Earths surace on a clear sum

mer day. Solar energy is composed o ultra

violet (UV) rays, visible light, and inrared

energy, each reaching the Earth in dierent

percentages: 5 percent o solar energy is

in the UV spectrum, including the type o

rays responsible or sunburn; 43 percent o

solar energy is visible light, in colors rang

ing rom violet to red; and the remaining

52 percent o solar energy is inrared, elt

as heat.

Cool Roof Market

The number o ENERGY STAR Cool

Roo Partners has grown rom 60 at

the programs inception to nearly 200

by the end o 2007; the number o

products has grown even aster, rom

about 100 to almost 1,600. Based

on 2006 data rom more than 150

ENERGY STAR Partners, shipments

o ENERGY STAR products constitute

about 25 percent o the commercial

roong market and about 10 percent

o the residential market. The overall

market share or these productsis rising over time, especially

with initiatives such as cool roo

requirements in Caliornia.

Cool roong reers to the use

o highlyreective and emissive

materials. Green roos reer to

rootop gardens.

Solar energy intensity varies over wavelengths rom about 250 to 2500 nanometers.

White or light colored cool roo products reect visible wavelengths. Colored cool

roo products reect in the inrared energy range.

REDUCING URBAN HEAT ISLANDS DRAFT2


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Manycool roo products are bright

white. These products get their high

solar refectance primarily rom

reecting in the visible portion

o the spectrum depicted in Figure

2. Given the desire or colored roo

products or many buildings, such as

the typical single amily home, manu

acturers are continuing to develop

cool colored products that reect in

the nearinrared range, or the in

rared wavelengths rom about 700 to

2500 nanometers shown in Figure 2.

1.2 Solar ReectanceSolar refectance, or albedo, is the percent

age o solar energy refected by a surace.

Researchers have developed methods to

determine solar refectance by measuring

how well a material refects energy at each

solar energy wavelength, then calculating

the weighted average o these values (see

Section 4.1). Traditional roong materi

als have low solar refectance o 5 to 15

percent, which means they absorb 85 to

95 percent o the energy reaching them

instead o refecting the energy back out to

the atmosphere. The coolest roo materi

als have a high solar refectance o more

than 65 percent, absorbing and transerring

to the building 35 percent or less o the

energy that reaches them. These materi

als refect radiation across the entire solar

spectrum, especially in the visible and

inrared (heat) wavelengths.

1.3 Thermal Emittance

Although solar refectance is the most im

portant property in determining a materials

contribution to urban heat islands, thermal

emittance is also a part o the equation. Any

surace exposed to radiant energy will get

Figure 3: Eect o Albedo on Surace

Temperature

Albedo alone can signicantly inuence surace

temperature, with the white stripe on the brick wall about5 to 10F (3-5C) cooler than the surrounding, darker areas.

hotter until it reaches thermal equilibrium

(i.e., it gives o as much heat as it receives).

A materials thermal emittance determines

how much heat it will radiate per unit area

at a given temperature, that is, how readily

a surace gives up heat. When exposed to

sunlight, a surace with high emittance will

reach thermal equilibrium at a lower tem

perature than a surace with low emittance,because the high-emittance surace gives o

its heat more readily.

ASUNationalCenteroExcellence

COOL ROOFS DRAFT 3


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The let hal o this traditional bitumen roo in Arizona

is shown in visible wavelengths and the right in

inrared. The roos temperature reaches almost

175F (80C).

Figure 4: Temperature o Conventional 1.4 Temperature EectsRoong Solar refectance and thermal emittance

have noticeable eects on surace tempera

ture. Figure 5 illustrates these dierences us

ing three dierent roo types. Conventional

ASUNationalCenteroExcellence roo suraces have low refectance but high

thermal emittance; standard black asphalt

roos can reach 165 to 185F (74 - 85C)

at midday during the summer. Bare metal

or metallic suraced roos have high refec

tance and low thermal emittance and can

warm to 150 to 165F (66 - 77C). Research

has shown that cool roos with both high

refectance and high emittance reach peak

temperatures o only 110 to 115F (43-46C)

in the summer sun. These peak values vary

by local conditions. Nonetheless, researchreveals that conventional roos can be 55

to 85F (31-47C) hotter than the air on

any given day, while cool roos tend to stay

within 10 to 20F (6-11C) o the back

ground temperature.3

Figure 5: Example o Combined Eects o Solar Reectance and

Thermal Emittance on Roo Surace Temperature4

black roof

low solar reflectancehigh emittance

180F

solar reflectance

92%

5%

60%

25%

75%

92%

emittance

160F 120F

metal roof

high solar reflectancelow emittance

white roof

very high reflectancehigh emittance

LisaGartland

On a hot, sunny, summer day, a black roo that reects 5 percent o the suns

energy and emits more than 90 percent o the heat it absorbs can reach

180F (82C). A metal roo will reect the majority o the suns energy while

releasing about a ourth o the heat that it absorbs and can warm to 160F

(71C). A cool roo will reect and emit the majority o the suns energy and

reach a peak temperature o 120F (49C).



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These reduced surace temperatures rom

cool roos can lower air temperature.

For example, a New York City simulation

predicted near-surace air temperature

reductions or various cool roo mitigation

scenarios. The study assumed 50-percent

adoption o cool roos on available roo

space and ran models to evaluate the

resulting temperature changes. Averaged

over all times o day, the model predicted

a city-wide temperature reduction o 0.3F

(0.2C). The city-wide, 3:00 p.m. average

reduction was 0.6F (0.3C) and ranged

rom 0.7 to 1.4F (0.4 - 0.8C) in six spe

cic study areas within the city.5

2 Cool Roo TypesThere are generally two categories o roos:

low-sloped and steep-sloped. A low-sloped

roo is essentially fat, with only enough

Steep-sloped roos have inclines greater

than a 2-inch rise over a 12-inch run. These

roos are ound most oten on residences

and retail commercial buildings and are

generally visible rom the street.

2.1 Low-Sloped Cool Roos

Low-sloped and steep-sloped roos use

dierent roong materials. Traditionally,

low-sloped roos use built-up roong or a

membrane, and the primary cool roo op

tions are coatings and single-ply membranes.

Figure 7: Cool Coating Being Sprayed

onto a Rootop

Cool coating being sprayed onto a rootop.

incline to provide drainage. It is usually

dened as having no more than 2 inches (5

cm) o vertical rise over 12 inches (30 cm)

o horizontal run, or a 2:12 pitch. These

roos are ound on the majority o com

mercial, industrial, warehouse, oce, retail,

and multi-amily buildings, as well as some

single-amily homes.

Cool Roo Coatings. Coatings are sur-Figure 6: Low-Sloped Cool Roo

ace treatments that are best applied to

LisaGartland/PositivEnergy

Buildings with a large roo area relative to building

height, such as this warehouse, make ideal

candidates or cool roong, as the roo surace area

is the main source o heat gain to the building.

RonWhipple/S

WDUrethane

low-sloped roos in good condition. They

have the consistency o thick paint and

contain additives that improve their adhe

sion, durability, suppression o algae and

ungal growth, and ability to sel-wash, or

shed dirt under normal rainall. Building

owners can apply cool roo coatings to a

wide range o existing suraces, includingasphalt capsheet, gravel, metal, and various

single-ply materials.

COOL ROOFS DRAFT 5


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When purchasing cool roo elasto

meric coatings, building owners can

require that products meet the

ASTM international standard,

ASTM D 608305e1, Standard Spec

ication or Liquid Applied Acrylic

Coating Used in Roong, to ensure

the product achieves certain speci

cations. There is currently no similar

standard or cementitious coatings.

There are two main types o cool roo

coatings: cementitious and elastomeric.

Cementitious coatings contain cement

particles. Elastomeric coatings includepolymers to reduce brittleness and im

prove adhesion. Some coatings contain

both cement particles and polymers. Both

types have a solar refectance o 65 per

cent or higher when new and have a ther

mal emittance o 80 to 90 percent or more.

The important distinction is that elasto

meric coatings provide a waterproong

membrane, while cementitious coatings

are pervious and rely on the underlying

roong material or waterproong.

Common CoolSingle-Ply Materials

EPDM (ethylene propylenediene monomer), a synthetic

rubber material, with seams that

must be glued or taped together.

CSPE (chlorosulonated poly-ethylene), a polymer material,

with seams that can be heat-

welded together.

PVC (polyvinyl chloride) andTPO (thermoplastic olefns),

thermoplastic materials, with seams

that can be heat-welded together.

SinglePly Membranes. Single-ply mem

branes come in a pre-abricated sheet that

is applied in a single layer to a low-sloped

roo. The materials are generally glued or

mechanically astened in place over the en

tire roo surace, with the seams sealed by

taping, gluing, or heat-welding. A number

o manuacturers ormulate these products

with cool suraces.

Building owners generally consider cool

roo options when their roo begins to

ail. They typically use a cool roo coat-

ingi an existing roo needs only moder

ate repair, and asingleply membraneor

more extensive repairs. The cut-o point

between moderate and extensive repairs is

not easily determined. In making a choice

between these options, however, build

ing owners can gather input rom many

sources, including roong consultants and

contractors, product manuacturers, and

contacts at other acilities that have had

cool roong installed.

2.2 Steep-Sloped Cool Roos

Most cool roo programs ocus on the low-

sloped roong sector, but cool roo optionsare becoming available or the steep-sloped

sector as well. Asphalt shingles are the

Figure 8: Conventional and Cool

Colored Tiles

W.A.M

iller/ORNL

Conventionallypigmented tiles on

battens

Cool colored tilesmounted directly

on deck

Cool colored tileson battens

Cool roo products can be indistinguishable rom

their conventional counterparts. The rightmost

row o curved tiles uses conventional colored

pigments, whereas the other two rows use cool

pigments.



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most common roong materials used on

steep-sloped roos. Other products include

metal roong, tiles, and shakes.

The market or steep-sloped cool roong

materials is growing, although the solar

refectance or these products is generally

lower than or low-sloped cool roos. A

number o products are available or tiles

and painted metal roong.

The solar refectance o traditional tiles,

typically made o clay or concrete, ranges

rom 10 to 30 percent. Manuacturers have

begun producing cool colored tiles that

contain pigments that refect solar energy

in the inrared spectrum. The ENERGY

STAR Roo Products List as o April 2008

Cool Colors

The Caliornia Energy Commission

has sponsored the Cool Colors

Project, under which LBNL and Oak

Ridge National Laboratory (ORNL)

are collaborating with roong indus

try partners to research and develop

cool colored roo products that could

expand signicantly the use o cool

roong in the residential sector. See

or more

inormation.

has approved tiles or steep-sloped roos

with initial solar refectances ranging rom

25 to almost 70 percent, depending oncolor. These tiles come in traditional col

ors, such as brown, green, and terra cotta.

They are durable and long-lasting, but not

widely used. Where tiles are used, the cool

tile alternatives can be available at little or

no incremental cost over traditional tiles.6

Figure 9: Cool Metal Roong

Cool colored metal roos lend themselves

readily to the steep-sloped market, as this house

demonstrates.

CRRC/Custom-B

iltMetals

Cool colored metal roong products alsouse inrared-refecting pigments and have

high durability and long lie. About one-

hal o the products on the ENERGY STAR

Roo Products List as o April 2008 were

metal roong products or steep-sloped

roos, with initial solar refectances ranging

rom about 20 to 90 percent.

Asphalt shingles are the most commonly

used material or steep-sloped roos, with a

market share o about 50 percent, dependingon the region,7 and a low initial cost o just

over $1.00 per square oot (0.930 m2). As o

April 2008, several manuacturers oered a

line o asphalt shingles on the ENERGY STAR

Roo Products List, with initial solar refec

tances ranging rom about 25 to 65 percent.

Other shingle products on the list are metal.

Manuacturers, researchers, and other stake

holders are working together to develop

additional, cool-colored shingle products that

use inrared-refecting pigments.8

COOL ROOFS DRAFT 7
http://coolcolors.lbl.gov/http://coolcolors.lbl.gov/


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3 Benefts and Costs

The use o cool roos as a mitigation strat

egy brings many benets, including lower

energy use, reduced air pollution and

greenhouse gas emissions, and improved

human health and comort. At the sametime, there can be a cost premium or some

cool roo applications versus traditional

roong materials. This section highlights

some o the key benets and costs o cool

roo programs and individual projects.

Section 6 also introduces cool roo energy

savings calculators that community plan

ners or individual building owners can use

to help determine whether to pursue cool

roos as a mitigation option.

3.1 Benets

Reduced Energy Use.A cool roo trans

ers less heat to the building below, so the

building stays cooler and more comortable

and uses less energy or cooling. Every

building responds dierently to the eects

o a cool roo. For example, Table 1 lists

examples o the general characteristics and

cooling energy savings o dierent one-

story buildings in Caliornia, Florida, andTexas. The measured savings varied rom

10 to almost 70 percent o each build

ings total cooling energy use. In addition,

a 2004 report summarized more than 25

articles about the cooling energy used by

buildings with cool roos and identied

energy savings ranging rom 2 to over 40

percent, with average savings o about 20

percent.9

Local climate and site-specic actors, suchas insulation levels, duct placement, and

attic conguration, play an important role

in the amount o savings achieved (see

the range in Table 1). Other site-specic

variables also can strongly infuence the

amount o energy a particular building

will save. For example, a study o a San

Jose, Caliornia, drug store documented

cooling energy savings o only 2 percent.

The cooling demands in this store were

driven by the design o the building, in

cluding a radiant barrier under the roo

and a well ventilated plenum space, so that

heat transer through the roo contributed

little to the stores cooling demand.10Thus,

in gauging potential energy savings or a

particular building, the building owners

will need to consider a range o actors to

make cool roong work or them.

Another benet o cool roong is that it

saves energy when most neededduring

peak electrical demand periods that gen

erally occur on hot, summer weekday

aternoons, when oces and homes are

running cooling systems, lights, and appli

ances. By reducing cooling system needs, a

cool roo can help building owners reduce

peak electricity demand. The last column in

Table 1 lists reductions in the peak demand

or cooling energy that range rom 14 to 38

percent ater installation o a cool roo.

Lower peak demand not only saves on total

electrical use but also can reduce demand

ees that some utilities charge commercial

and industrial building owners. Unlike

residential customers, who pay or only the

amount o electricity they use, commercial

and industrial customers oten pay an ad

ditional ee based on the amount o peak

power they demand. Because cool roong

helps reduce their peak demand, it lowers

these costs.

Insulation and R-Values

The R-value o building insulation

indicates its ability to impede heat

fow. Higher R-values are correlated

with greater insulating properties.



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Researchers have conducted in-depth mod

eling to assess how building-level energy

savings can aect city-wide energy usage.

The Lawrence Berkeley National Labora

tory (LBNL) ran simulations to evaluate

the net energy impacts o applying cool

roong in 11 U.S. cities.11The original

study was based on 1993 energy prices and

buildings that use electrical cooling sys

tems and gas urnaces. Figure 10 uses 2003

state-level prices or electricity and natural

gas, based on Energy Inormation Adminis

tration data or the commercial sector.

Cool roos refect solar energy year round,

which can be a disadvantage in the win

ter as they refect away desirable winter

time heat gain. The net eect is generally

positive, though, because most U.S. cities

have high cooling and peak cooling de

mand, and electricity is expensive. Figure

10 presents the total anticipated cooling

energy savings and the net savings a

ter considering increased heating costs.

Although northern and mid-Atlantic cities

with relatively long heating seasons, such

as Chicago, Philadelphia, and Washington

D.C., still reap net savings, the net benets

or New York City remain particularly high

because o the high price o electricity in

that area. (See Section 3.2 or urther dis

cussion o the heating penalty.)

This same LBNL study extrapolated the

results to the entire United States and es

timated that widespread use o cool roos

Table 1: Reported Cooling Energy Savings rom Buildings with Cool Roos12

Annual Peak

Size Roo Roo Cooling Demand

Building Location Citation (t2) Insulation* Space Saved Savings

Residence Merritt

Island, FL

(Parker, D., S. Barkaszi,

et al. 1994)

1,800 R-25 Attic 10% 23%

Convenience

Retail

Austin, TX (Konopacki, S. and H.

Akbari 2001)

100,000 R-12 Plenum 11% 14%

Residence Cocoa

Beach, FL

(Parker, D., J. Cum

mings, et al. 1994)

1,795 R-11 Attic 25% 28%

Residence Nobleton,

FL

(Parker, D., S. Barkaszi,

et al. 1994)

900 R-3 Attic 25% 30%

School

Trailer

Volusia

County, FL

(Callahan, M., D.

Parker, et al. 2000)

1,440 R-11 None 33% 37%

School

Trailer

Sacramento,

CA

(Akbari, H., S. Bretz, et

al. 1993)

960 R-19 None 34% 17%

Our Saviors

School

Cocoa

Beach, FL

(Parker, D., J. Sherwin,

et al. 1996)

10,000 R-19 Attic 10% 35%

Residence Cocoa

Beach, FL

(Parker, D., J. Cum

mings, et al. 1994)

1,809 None Attic 43% 38%

Residence Sacramento,

CA

(Akbari, H., S. Bretz, et

al. 1993)

1,825 R-11 None 69% 32%

* Note: These insulation levels are lower than the energy efciency levels recommended by ENERGY STAR. I insulation

levels were higher, the cooling savings likely would be less.

COOL ROOFS DRAFT 9


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could reduce the national peak demand or

electricity by 6.2 to 7.2 gigawatts (GW),13

or the equivalent o eliminating the need to

build 12 to 14 large power plants that have

an energy capacity o 500 megawatts each.

Reduced Air Pollution and Greenhouse

Gas Emissions.The widespread adop

tion o heat island mitigation eorts such

as cool roos can reduce energy use dur

ing the summer months. To the extent that

reduced energy demand leads to reduced

burning o ossil uels, cool roos contrib

ute to ewer emissions o air pollutants,

such as nitrogen oxides (NOX), as well as

greenhouse gases, primarily carbon dioxide

(CO2). The CO2 reductions can be sub

stantial. For example, one study estimated

potential CO2 reductions o 6 to 7 percent

in Baton Rouge and Houston rom reduced

building energy use.14 Reductions in air

pollutant emissions such as NOXgener

ally provide benets in terms o improved

air quality, particularly ground-level ozone

Case Examples of Building Comfort Improvements

Bigbox retailer Home Base, Vacaville, Caliornia.15 Installing a cool roo atthis store helped solve the problem created by an incorrectly sized cooling sys

tem. This store used an undersized evaporative cooling system that was unable to

meet the buildings cooling loads. Indoor temperatures above 90F (32C) were

recorded, even with the building coolers working around the clock. Ater adding

a cool roo, peak indoor temperatures were reduced to 85F (29C) or lower, and

10 more shopping hours a week were deemed comortable (below 79F (26C)

and 60 percent humidity) inside the store. Although the evaporative coolers were

still not powerul enough to meet the hottest conditions, the cool roo helped

reduce temperatures inside the store.

Apartment complex, Sacramento, Caliornia.16Adding cool roos at theseresidences lowered indoor air temperatures, improving resident comort. These

non-air conditioned buildings were composed o two stories and an attic, with an

R-38 level o insulation above the second story and below the attic space. Adding

a cool roo lowered peak air temperatures in the attic by 30 to 40F (17-22C).

Generally, the higher the insulation level, the less eect a cool roo will have on

the space beneath it; however, in this case, even with high insulation levels, the

cool roo reduced second-story air temperatures by 4F (2C) and rst foor tem

peratures by 2F (1C).

Private elementary school, Cocoa Beach, Florida.17 Cool roo coatings at thisschool improved comort and saved energy. This 10,000-square oot (930 m2)

acility had an asphalt-based roo, gray modied bitumen, over plywood decking

with a measured solar refectance o 23 percent. The dropped ceiling was insu

lated to R-19 levels, and insulated chiller lines were used in the hot roo plenum

space. Once the roo was covered by an acrylic white elastomeric coating, the so

lar refectance rose to 68 percent. The classrooms became cooler and the chiller

electric use was reduced by 10 percent. School sta noticed improved comort

levels due to the new roo.



14/31

Atlant

a

Chica

go

LosAn

geles

FortW

orth

Houst

on

Miami

NewOrlea

ns

NewYork

City

Philade

lphia

Phoen

ix

Washingt

on,D

.C.

Avera

ge

Figure 10: Modeled Net Energy Cost Savings* ($/1,000 t2) in Various U.S. Cities rom Widespread Use

o Cool Roong18

$50

Cooling Savings (2003$/1000 ft2)$45 Net Savings (2003$/1000 ft2)

$40

$35

2003Dollars

$30

$25

$20

$15

$10

$5

$0

Costs are based on state-specic data applied to each city, using 2003 Energy Inormation Administration reported

prices or the commercial sector.19

(smog). The relationships between pollut

ant reductions and improved air quality are

complex, however, and require air quality

modeling to demonstrate the benets in

specic urban areas.

Improved Human Health and Comort.Ceilings directly under hot roos can be

very warm. A cool roo can reduce air tem

peratures inside buildings with and with

out air conditioning.

For residential buildings without air condi

tioning, cool roos can provide an important

public health benet during heat waves. For

example, Philadelphia operates a program

to add cool roos and insulation to residen

tial buildings that lack air conditioning toprevent heat-related illnesses and deaths. A

study measured signicant cooling benets

rom this program.20The study controlled

Figure 11: Cool Roong on Urban Row

Homes

Philadelphia reduced temperatures in row houses

by installing cool roos, which improves the

comort or occupants and may help reduce deaths

rom excessive heat events. Baltimore, with similar

building stock, took similar steps ollowing the

success in Philadelphia.

EnergyCoordinatingAgency,Ph

iladelphia

room air temperatures dropped by about

2.4F (1.3C). The study noted that on a 95For dierences in outside temperature be

(35C) day, these types o reductions rep-ore and ater the installing the cool roos

and insulation; these treatments lowered theresent large reductions in heat gain to the

room and signicantly improve perceiveddaily maximum ceiling surace temperature

human comort.by about 4.7F (2.6C), while daily maximum

COOL ROOFS DRAFT 11


15/31

3.2 Potential Adverse Impacts

Cool roos can have a wintertime heating

penalty because they refect solar heat that

would help warm the building. Although

building owners must account or this pen

alty in assessing the overall benets o coolroong strategies, in most U.S. climates this

penalty is not large enough to negate the

summertime cooling savings because:

The amount o useul energy refectedby a cool roo in the winter tends to be

less than the unwanted energy refected

in the summer. This dierence oc

curs primarily because winter days are

shorter, and the sun is lower in the sky.

The sunlight strikes the Earth at a lowerangle, spreading the energy out over a

larger area and making it less intense.

In mid-Atlantic and northern states with

higher heating requirements, there also

are more cloudy days during winter,

which reduces the amount o sun re

fected by a cool roo. Snow cover on

roos in these climates also can reduce

the dierence in solar refectivity be

tween cool and non-cool roos.

Many buildings use electricity or cooling and natural gas or heating. Electrici

ty has traditionally been more expensive

than natural gas per unit o energy, so

the net annual energy savings translate

into overall annual utility bill savings.

Note, however, that natural gas and elec

tricity prices have been volatile in some

parts o the country, particularly since

2000. As shown in Figure 10, with el

evated natural gas prices in recent years,

the net benet in terms o cost savingsmight be small in certain northern cities

with high heating demands.

Caliornia-based research indicates a

cost premium ranging rom zero

to 20 cents per square oot or cool

roo products.

3.3 Costs

A 2006 report (see Table 2) investigated the

likely initial cost ranges or various cool

roo products.21The comparisons in Table

2 are indicative o the trade-os in cost and

refectance and emittance actors between

traditional and cool roo options. For low-

sloped roos, the report noted that:

Cool roo coatings might cost between $0.75 and $1.50 per squareoot or materials and labor, which

includes routine surace preparation

like pressure-washing, but which does

not include repair o leaks, cracks, or

bubbling o the existing roo surace.

Single-ply membrane costs vary rom$1.50 to $3.00 per square oot, including

materials, installation, and reasonable

preparation work. This cost does not in

clude extensive repair work or removaland disposal o existing roo layers.

For either type o cool roo, there canbe a cost premium compared to other

roong products. In terms o dollars

per square oot, the premium ranges

rom zero to 5 or 10 cents or most

products, or rom 10 to 20 cents or a

built-up roo with a cool coating used

in place o smooth asphalt or alumi

num coating. As with any roong job, costs depend

on the local market and actors such as

the size o the job, the number o roo

penetrations or obstacles, and the ease

o access to the roo. These variables

oten outweigh signicantly the dier

ence in costs between various roong

material options.22



16/31

Table 2: Comparison o Traditional and Cool Roo Options23

Warmer Roo Options Cooler Roo Options

Roo Type Reectance Emittance

Cost

($/t2) Roo Type Reectance Emittance

Cost

($/t2)

Built-up Roo

With dark gravel

With smooth asphalt

surace

With aluminum coating

0.08-0.15

0.04-0.05

0.25-0.60

0.80-0.90

0.85-0.95

0.20-0.50

1.2-2.1 Built-up Roo

With white gravel

With gravel and

cementitious coating

Smooth surace with

white roo coating

0.30-0.50

0.50-0.70

0.75-0.85

0.80-0.90

0.80-0.90

0.80-0.90

1.2-2.15

Single-Ply Membrane

Black (PVC) 0.04-0.05 0.80-0.90

1.0-2.0 Single-Ply Membrane

White (PVC)

Color with cool

pigments

0.70-0.78

0.40-0.60

0.80-0.90

0.80-0.90

1.0-2.05

Modifed Bitumen

With mineral surace

capsheet (SBS, APP)

0.10-0.20 0.80-0.90

1.5-1.9 Modifed Bitumen

White coating over a

mineral surace (SBS,

APP)

0.60-0.75 0.80-0.90

1.5-1.95

Metal Roo

Unpainted, corrugated

Dark-painted,

corrugated

0.30-0.50

0.05-0.08

0.05-0.30

0.80-0.90

1.8-3.7 Metal Roo

White painted

Color with cool

pigments

0.60-0.70

0.40-0.70

0.80-0.90

0.80-0.90

1.8-3.75

Asphalt Shingle

Black or dark brown

with conventionalpigments

0.04-0.15 0.80-0.90

0.5-2.0 Asphalt Shingle

White (light gray)

Medium gray or brownwith cool pigments

0.25-0.27

0.25-0.27

0.80-0.90

0.80-0.90

0.6-2.1

Liquid Applied

Coating

Smooth black

0.04-0.05 0.80-0.90

0.5-0.7 Liquid Applied Coating

Smooth white

Smooth, of-white

Rough white

0.70-0.85

0.40-0.60

0.50-0.60

0.80-0.90

0.80-0.90

0.80-0.90

0.6-0.8

Concrete Tile

Dark color with

conventional pigments

0.05-0.35 0.80-0.90

1.0-6.0 Concrete Tile

White

Color with cool

pigments

0.70

0.40-0.50

0.80-0.90

0.80-0.90

1.0-6.0

Clay Tile

Dark color with

conventional pigments

0.20 0.80-0.90

3.0-5.0 Clay Tile

White

Terra cotta (unglazed

red tile)

Color with cool pigments

0.70

0.40

0.40-0.60

0.80-0.90

0.80-0.90

0.80-0.90

3.0-5.0

Wood Shake

Painted dark color with

conventional pigment

0.05-0.35 0.80-0.90

0.5-2.0 Wood Shake

Bare 0.40-0.55 0.80-0.90

0.5-2.0

COOL ROOFS DRAFT 13


17/31

3.4 Benet-Cost Considerations

Based on the benets o cool roos and the

cost premiums noted in Table 2, a commu

nity can develop a benet-cost analysis to

determine whether a cool roo project or

program will provide overall net benetsin a given area. For example, the cost study

reerenced in Table 2 also evaluated the

cost eectiveness o low-sloped cool roos

or commercial buildings in Caliornia by

quantiying ve parameters (see summary

results in Table 3):24

Annual decrease in cooling electricityconsumption

Annual increase in heating electricityand/or gas

Net present value (NPV) o netenergy savings

Cost savings rom downsizing coolingequipment

Cost premium or a cool rooThe study recognized that other parameters

can provide benets or reduce costs that

were not part o the analysis. These include:

Reduced peak electric demandor cooling

Financial value o rebates or energysaving incentives that can oset the cost

premiums or cool roong materials

Reduced material and labor costs overtime resulting rom the extended lie

o the cool roo compared to a tradi

tional roo

Given the inormation at hand, the studyound that expected total net benets, ater

considering heating penalty costs, should

range rom $0.16 to $0.66/square oot

(average $0.47/t2) based on the Caliornia

climate zones studied (see Table 3). Cali

ornia relied in part on this benet-cost

analysis to establish mandatory statewide

low-sloped cool roo requirements.

In 2006, Caliornia began evaluating wheth

er to extend the states mandatory cool roo

requirements to the steep-sloped market.

One analysis in support o this approach

anticipated positive cost eectiveness in

many but not all Caliornia climate zones.25

The state will consider that analysis, as

well as public comments on benets and

costs in deciding what nal action to take

on steep-sloped roo requirements. A nal

rule is expected in 2008.

Although the results o Table 3 are specic

to Caliornia in terms o electricity rates

and typical cooling and heating energy use,

the cost eectiveness approach can be rep

licated by other communities considering

cool roo projects or programs.

Figure 12: Cool Roo on a Condominium

Homeowners can also reap the benets o cool roos.

GaryCook



18/31

Table 3: Example Cool Roo Cost/Benet Summary or Caliornia26

Caliornia Annual Energy/1000 t2 Peak Power/1000 t2 Net Present Value (NPV)/1000 t2

Climate

Zone

Roo

R-Value kWh therm

Source

MBTU kW $equip $kWh $therm $energy $total

1 19 115 -8.3 0.3 0.13 67 157 -62 95 1622 19 295 -5.9 2.4 0.20 100 405 -43 362 462

3 19 184 -4.9 1.4 0.15 76 253 -35 218 294

4 19 246 -4.2 2.1 0.18 90 337 -31 306 396

5 19 193 -4.7 1.5 0.17 83 265 -35 230 313

6 11 388 -4.1 3.6 0.22 111 532 -29 503 614

7 11 313 -2.6 2.9 0.25 125 428 -20 408 533

8 11 413 -3.7 3.9 0.25 125 565 -28 537 662

9 11 402 -4.5 3.7 0.20 101 552 -33 519 620

10 19 340 -3.6 3.1 0.18 89 467 -26 441 530

11 19 268 -4.9 2.3 0.15 75 368 -37 331 406

12 19 286 -5.3 2.4 0.19 95 392 -39 353 448

13 19 351 -5.1 3.1 0.19 96 480 -37 443 539

14 19 352 -4.7 3.1 0.21 105 483 -33 450 555

15 19 380 -1.7 3.7 0.16 82 520 -13 507 589

16 19 233 -10.6 1.3 0.18 90 319 -78 242 332

min

max

avg

115

413

297

-10.6

-1.7

-4.9

0.3

3.9

2.6

0.13

0.25

0.19

67

125

94

157

565

408

-78

-13

-36

95

537

372

162

662

466

* This table presents dollar savings rom reduced air conditioning use (in kWh) and reduced air conditioning equipment

sizing ($equip), oset by natural gas heating penalty costs (measured in therms). The Net Present Value (NPV)/1000 t2

column uses the kWh and therm inormation to project savings or energy only and in total (energy plus equipment).

COOL ROOFS DRAFT 15


19/31

4 Other Factors to Consider

4.1 Product Measurement

To evaluate how cool a specic prod

uct is, ASTM International has validated

test methods to measure solar refectance

and thermal emittance (see Table 4). The

Cool Roo Rating Council (CRRC) also has

developed a test method or variegated

roo products such as composite shingles,

including laboratory and eld tests. Labo

ratory measurements help determine the

properties o new material samples, while

eld measurements are useul or evaluat

ing how well a roo material has withstood

the test o time, weather, and dirt.

The nal method listed in Table 4 is not an

actual test but a way to calculate the solar

refectance index or SRI. The SRI is a value

that incorporates both solar refectance and

thermal emittance in a single value to rep

resent a materials temperature in the sun.

This index compares how hot a surace

would get compared to a standard black

and a standard white surace. In physical

terms, this scenario is like laying a roo ma

terial next to a black surace and a white

surace and measuring the temperatures o

all three suraces in the sun. The SRI is a

value between zero (as hot as a black sur

ace) and 100 (as cool as a white surace)

and calculated as ollows:

(Tblack Tsurace)SRI= x 100

(Tblack Twhite)

Table 4: Test Methods to Evaluate Coolness o Roong Materials

Property Test Method Equipment Used Test Location

Solar

reectance

ASTM E 903 - Standard Test Method or Solar Absorp

tance, Reectance, and Transmittance o Materials

Using Integrating Spheres

Integrating sphere

spectrophotometer

Laboratory

Solar

reectance

ASTM C 1549 - Standard Test Method or Determina

tion o Solar Reectance Near Ambient Temperature

Using a Portable Solar Reectometer

Portable solar

reectometer

Laboratory or

eld

Solar

reectance

ASTM E 1918 - Standard Test Method or Measuring

Solar Reectance o Horizontal and Low-Sloped Sur

aces in the Field

Pyranometer Field

Solar

reectance

CRRC Test Method #1 (or variegated roo products,

[i.e. products with discrete markings o dierent col

ors]); used in conjunction with ASTM C1549

Portable solar

reectometer

Laboratory or

eld

Thermal

emittance

ASTM E 408-71 - Standard Test Method or Total

Normal Emittance o Suraces Using Inspection-Meter

Techniques

Reectometer or

emissometer

Laboratory

Thermal

emittance

ASTM C 1371 - Standard Test Method or

Determination o Emittance o Materials Near Room

Temperature Using Portable Emissometers

Emissometer Field

Solar

reectance

index

ASTM E 1980 - Standard Practice or Calculating Solar

Reectance Index o Horizontal and Low-Sloped

Opaque Suraces

None (calculation) --



20/31

The U.S. Green Building Council, as

part o its Leadership in Energy

and Environmental Design (LEED)

Rating System, has developed an

SRI Calculator to assist project spon

sors in calculating a roos SRI under

LEED-NC, Version 2.2, Sustainable

Site Credit 7.2: Heat Island Eect:

Roo. See .

4.2 Product Labeling

ENERGY STAR or Roo Products and the

Cool Roo Rating Council (CRRC) both

operate voluntary labeling programs ormanuacturers. Many building codes and

energy eciency rebate programs require

that cool roong materials meet recognized

specications and standards, and that a

vendors product be listed with either or

both o these voluntary labeling programs.

Figure 13: Olympic Oval, Salt Lake City, Utah

The Olympic Oval eatures a cool roo covering

almost 205,000 square eet (19,000 m2). ENERGY

STAR partners, who helped build the ovals roo,

have played key roles in advancing cool roong

technology.

SikaSarnafl,Inc.

ENERGY STAR or Roo Products. Manu

acturers can participate voluntarily in the

ENERGY STAR or Roo Products program.

A product qualies or ENERGY STAR i

it meets the solar refectance criteria ex

pressed in Table 5. The program uses sig

nicantly dierent criteria or low-sloped

versus steep-sloped roo products. Highly

refective products, which are currently

bright white or the most part, are available

or low-sloped roos. For aesthetic reasons,

bright white options are generally not

marketable or steep-sloped roos. Instead,

steep-sloped cool roo products generally

use moderately refective, colored options.

Version 2.0 o the program guidelines be

came eective in January 2008. The guide

lines require manuacturers to test their

products initial solar refectance and main

tenance o solar refectance ater at least

three years o service. For the initial testing,

manuacturers can rely on tests conducted

or purposes o certiying a product under

the Cool Roo Rating Councils Product Rat

ing Program, i applicable. To ensure the

long-term integrity o refective products,

ENERGY STAR also requires products tomaintain warranties comparable to those

oered or non-refective roo products. Fi

nally, the Version 2.0 guidelines also require

manuacturers to report a products initial

emissivity as part o the application process.

There is no emissivity level required, but

this inormation can provide valuable inor

mation on the potential savings and benets

The most up-to-date list oENERGY

STAR qualifed roo products,

and current, proposed, and prior

specications, can be ound on the

ENERGY STAR Web site at .

COOL ROOFS DRAFT 17
http://www.usgbc.org/http://www.energystar.gov/http://www.energystar.gov/http://www.energystar.gov/http://www.energystar.gov/http://www.usgbc.org/


21/31

Table 5: ENERGY STAR or Roo Products (Version 2.0) Qualiying Criteria

Type o Roo Product

Initial Solar Reectance Maintenance o Solar Reectance*

Standard Test Methods Standard Test Methods

Low-sloped 65% or higher ASTM E 903 or

ASTM C 1549**

50% or higher ASTM E 1918 or

ASTM C 1549

Steep-sloped 25% or higher ASTM E 903 or

ASTM C 1549**

15% or higher ASTM C 1549

* Maintenance o solar reectance is measured on a roo that has been in service or three years or more.

** Manuacturers can also use CRRC Test Method #1 or variegated roo products and can use results rom tests

conducted as part o CRRC Product Rating Program certication.

o a specic product in the region where it

will be used.

Based on data rom almost 90 percent o

the ENERGY STAR Partners, the market

share o cool roo products rom these

manuacturers has grown in recent years.

In 2004, cool roo products represented 8

percent o these manuacturers shipments

in the commercial roong sector and 6

percent in the residential. In 2006, their

shipments o commercial cool roo product

tripled to represent more than 25 percent

o their commercial roo products, and theresidential share almost doubled, reaching

10 percent.

Cool Roo Rating Council. CRRC is a non

prot organization with members rom the

business, consulting, and research elds.

The CRRC was ormed in 1998 and applied

to join the American National Standards

Institute (ANSI) ten years later. In Septem

ber 2002, CRRC launched its product rating

program with a list o solar refectance andthermal emittance values o roong materi

als. As o February 2007, this list included

only initial or new values o roong mate

rial properties, but work is underway to

add three-year weathered values to the list.

The weathered values o solar refectance

and thermal emittance will come rom

test arms located in dierent areas o the

country, where roo materials are exposed

to the elements or three years.

See the CRRC Rated Product

Directoryat .

Manuacturer participation in the CRRC

program is entirely voluntary. Participat

ing manuacturers must adhere to stringent

requirements; however, to ensure accurate

reported values, only agencies or laboratories accredited by CRRC can perorm tests,

and their test programs must use the ASTM

and CRRC standards listed in Table 4.

A material does not need to meet a solar

refectance or thermal emittance value to

appear on the CRRC Rated Product Direc

tory roong products list. Because any

product can be listed, regardless o how

cool it might be, it is up to the consumer

to check the values on the CRRC list anddecide which products meet their own

criteria or cool materials. Building own

ers and heat island mitigation groups can

use the CRRC ratings in conjunction with

the ENERGY STAR guidelines to help to

identiy cool materials on the basis o solar

refectance.

http://www.coolroofs.org/http://www.coolroofs.org/


22/31

4.3 Installation and Maintenance

A coating or single-ply membrane on a

low-sloped roo can serve as the top sur

ace o a roong assembly and can be

applied directly over a roo deck or on top

o other existing materials. Proper installation is important to the long-term success

o a cool roo project. For example, when

applied properly, many cool roo coatings

have been shown to last more than 20

years. When applied poorly, cool roo coat

ings can peel or fake o the roo within

a couple o years. To ensure good product

perormance, building owners can seek ap

propriate warranties or both the product

and the installation service.

On steepsloped roos, proession

als do not recommend using cool

coatings over existing shingles. This

technique can cause moisture prob

lems and water damage because the

coating can inhibit normal shingle

drying ater rain or dew accumula

tion, allowing water to condense and

collect under the shingles.

A key concern or cool roos is maintain

ing their high solar refectance over time.

I a buildings roo tends to collect large

amounts o dirt or particulate matter, wash

ing the roo according to the manuactur

ers recommended maintenance procedures

can help retain solar refectance. Also,

smoother suraces and higher sloped suraces tend to withstand weathering better.

With proper maintenance, coatings are able

to retain most o their solar refectance,

with decreases o only about 20 percent,

usually in the rst year ater application o

the coating.27

Figure 14: Installation o a Cool Single-

Ply Membrane

Cool roos can be applied to existing buildings or

designed into new ones.

LisaGartland/PositivEnergy

4.4 Cool Roong and Insulation

Cool roong and roo insulation are not

comparable options or saving building

energythey work very dierently. Build

ing owners must make separate decisions

to upgrade roo insulation levels or install

cool roong.

Some studies have evaluated the insula

tion levels needed to produce the same

summertime energy savings as a cool

roo.28,29,30These studies have been used

to support building codes that allow

less roo insulation i cool roong is in

stalled.31,32The conditions or choosing

levels o roo insulation or cool roong

vary based on climate, utility prices, build

ing use, building and re code consider

ations, and preerence. Thus, the ollowing

actors or choosing insulation or cool

roong are general approximations. Build

ing owners might consider adding roo or

ceiling insulation i:

There is less roo insulation thancalled or in the latest state or local

building codes

COOL ROOFS DRAFT 19


23/31

The building is in a climate with signicant cold weather or heating needs

The roo accounts or much o thebuildings envelope (i.e., the roo area

equals or exceeds one-ourth o the

buildings exterior surace area, calculated as the walls plus the roo).

Cool roong can be used on any building,

but is especially useul i:

The building is in a climate with hotand sunny weather during at least part

o the year (80F or hotter weather with

clear skies or at least three months o

the year)

Signicant cooling energy is used(three or more months o cooling use) The duct system is in the attic or ple

num space

There are problems maintaining indoorcomort in the summer (i air condi

tioning equipment cannot maintain

the desired temperature, or without air

conditioning, i indoor temperatures

exceed 80F)

The roo accounts or much o thebuildings envelope (i.e., the roo areaequals or exceeds one-ourth o the

buildings exterior surace area, calcu

lated as the walls plus the roo)

The roo materials tend to crack andage prematurely rom sun damage (i

damage begins beore the warranty

period or the roo lie ends).

Generally, adding roo insulation means

adding insulation under the roo or abovethe ceiling, which can be disruptive to

building occupants. Another option on

the market is to spray insulating oam or

ax rigid insulation onto the top o the

roo surace. Each o these products adds

approximately an R-6 level o long-term

thermal resistance or each inch (2.5 cm)

o thickness added. These technologies by

themselves are not cool roong materials;

however, they are oten applied as part

o a complete roong system, where the

top surace is a cool coating or single-ply

membrane.

5 Cool Roo Initiatives

Communities have developed cool roo

programs by taking action in their own

buildings, oten called leading by example;

through voluntary incentives; and through

mandatory requirements.

Local governments have requently started

by installing cool roos in public build

ings. Their eorts have included launchingdemonstration projects and adapting public

building procurement practices to require

cool roos or new public buildings and

roong renovation projects. Beginning with

the public sector allows a community to

demonstrate the technology, make contrac

tors aware o the products available, and

promote the use o cool roo materials in

other building sectors.

In many communities, voluntary cool rooincentives have been provided by local

energy companies as part o their demand-

side management programs. A ew local

government agencies also oer incentives

to assist low-income or other households

with installing cool roos.

Some governments have mandated imple

mentation o cool roos in certain areas.

These actions generally require adopting

specic energy code provisions that requirecool roos or include cool roos in the

calculation o how much insulation is re

quired to meet minimum energy eciency

requirements.



24/31

Mandatory requirements or cool roos

have played an increasingly signicant role

in implementation. Beore 1995, the only

regulations aecting cool roong mandated

that roo color not cause undue glare. The

American Society o Heating, Rerigerating,

and Air-conditioning Engineers (ASHRAE)

has since developed energy-ecient design

standards that provide minimum require

ments or both commercial and residential

buildings. ANSI/ASHRAE/IESNA Standard

90.1-1999,Energy Standards or Build-

ings Except LowRise Residential Buildings

and ANSI/ASHRAE Standard 90.2-2001,

EnergyEfcient Design o LowRise Resi-

dential Buildingsprovide guidelines or

new equipment, systems, and buildings.These standards were originally developed

in response to the 1970s energy crisis and

now serve as the generally accepted basis

or many state building and energy codes.

Both ASHRAE standards include credits

pertaining to cool roong. An example

o a cool roong credit is Addendum to

90.2-2001, which allows the use o high-

albedo roos in hot and humid climates as

part o the energy eciency ceiling calcula

tion or a residential building.33

A number o states and localities now have

developed specic energy code require

ments to encourage or require cool roong.

For example:

In 1995, Georgia was the rst stateto add cool roos to its energy code.

The code allowed building owners to

reduce roo insulation i they installed

a cool roo that had a minimum solarrefectance o 75 percent and a mini

mum thermal emittance o 75 percent.34

Note that i a building owner uses less

insulation when installing a cool roo,

he may not accrue net energy savings.

Florida is using a similar approach toGeorgia in its energy code.35 Because

o the energy eciency gains rom cool

roos, the Florida code allows com

mercial and multi-amily residential

buildings using a roo with at least 70

percent solar refectance and 75 percent

thermal emittance to reduce the amount

o insulation required to meet building

energy eciency standards. The ad

justment does not apply or roos with

ventilated attics or semi-heated spaces.

In January 2003, Chicago amendedits energy code requirements or low-

sloped roos.36This code applies to all

buildings except separated buildings

that have minimal peak rates o energy use and buildings that are neither

heated nor cooled. Low-sloped roos

installed on or beore December 31,

2008, must achieve a minimum solar

refectance (both initial and weathered)

o 0.25 when tested in accordance with

ASTM standards E 903 and E 1918 or

by testing with a portable refectometer

at near ambient conditions. For low-

sloped roos installed ater that date,

roong products must meet or exceedthe minimum criteria to qualiy or the

ENERGY STAR Roo Products label.

In 2001, in response to electrical powershortages, Caliornia updated its build

ing energy code (Title 24), adding cool

roong as an energy eciency op

tion.37A cool roo is dened as having

minimum solar refectance o 70 per

cent and minimum thermal emittance

o 75 percent, unless it is a concrete

or clay tile, in which case it can havea minimum solar refectance o 40

percent. This 40 percent rating incor

porates new cool colored residential

products. Owners must use specic

methods to veriy building energy use

to account or cool roong as an energy

eciency option. In this case, the heat

COOL ROOFS DRAFT 21


25/31

gain o the roo is reduced to account

or use o a cool roo. In 2005, these

cool roo provisions became mandatory

or all new non-residential construc

tion and re-roong projects that involve

more than 2,000 square eet (190 m2)

or 50 percent replacement. The code

also provides alternatives to the stan

dard criteria as additional compliance

options. In 2006, Caliornia began con

sidering planned 2008 updates to Title

24 and is studying the possibility o

extending cool roo requirements to the

steep-sloped market.38

For urther inormation on CaliorniaTitle 24, see .

Table 6 lists many o the primary types o

cool roo activities. The Heat Island Re

duction Activities chapter provides more

detailed examples.

6 Resources6.1 Cool Roo Energy Savings Calculators

Federal agencies have developed two Web-

based calculators that compare energy

and cost savings rom dierent cool roo

technologies or various building types.

Consumers also can nd calculator tools on

Web sites o cool roo product manuactur

ers. All o these tools use dierent assump

tions and ormulas and generate dierent

results; thereore, they provide a range opotential impacts rather than precise state

ments o the savings any individual build

ing owner will obtain.

Figure 15: Aerial View o Sacramento,

Caliornia, with Capitol

Caliornias Title 24 has accelerated the diusion

o cool roong across the state. The reective roo

o the capitol in Sacramento and other buildings

around Capitol Park stand out among the

vegetation, pavement, and darker roos.

GoogleEarth

ENERGY STAR Roofng Comparison

Calculator.The Web-based ENERGY STAR

Roong Comparison Calculator helps to

estimate the energy and money that can

be saved by using ENERGY STAR roong

products on air-conditioned buildings o at

least 3,000 square eet (280 m2). This cal

culator estimates savings o typical build

ing types with non-metallic-suraced roos

under typical weather conditions.

This EPA calculator requires input on the

age, type, and location o the building; the

eciency o the heating and cooling sys

tems; the local cost o energy; and inorma

tion about the roo area, insulation levels,

and type o roong systems used. Based on

these actors, the tool provides an estimate

o annual electricity savings in kWh and

dollars per 1,000 square eet (93 m2). The

annual eects o any heating penalties are

included, given in therms and dollars per

1,000 square eet i natural gas is used to

uel the heating system, or subtracted rom

the annual electricity savings i an electric

heat pump is used. This calculator does not

model electric resistance heating systems.

http://www.energy.ca.gov/efficiency/blueprint/index.htmlhttp://www.energy.ca.gov/efficiency/blueprint/index.htmlhttp://www.energy.ca.gov/efficiency/blueprint/index.htmlhttp://www.energy.ca.gov/efficiency/blueprint/index.html


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Table 6: Examples o Cool Roo Initiatives

Type o Initiative Description Links to Examples

Research National

laboratories

- The Heat Island Group at Lawrence

Berkeley National Laboratory provides research and inormation about

cool roong and other heat island mitigation measures. The Cool Roong

Materials Database lists the solar reectance and thermal emittance o

numerous roo products, including cool colored roong.

- ORNL conducts research on reective roong and solar

radiation control. Its Web site includes act sheets, a cool roo calculator,

background inormation about cool roong, and research publications.

Voluntary eorts Demonstration

programs

- Tucson,

Arizona, Cool Roo Demonstration Project (city ofce building).

Incentive

programs

- Pacic Gas & Elec

trics utility rebate program or cool roos.

- Southern Caliornia Edisons Cool

Roo Rebate Program.

Austin Energys Relective Roo Coating and Roo and Ceiling Insulation

rebate inormation.

- Chicago announced in Fall 2007 that it

was expanding a green roo grant program to include cool roos, with up to

55 $6,000 grants targeted per year; see inormation under Department o

Environment portion o the Citys website.

Outreach &education

- EPAs Heat Island Reduction Initiative provides inormation on the temperature, energy, and air quality impacts rom

green roos and other heat island mitigation strategies.

Weatherization

programs

- Philadelphia cool roo

incentive program or low-income housing.

Policy eorts State and munici

pal energy codes

that require or

provide recogni

tion o cool roos

- Caliornia building energy

code that requires cool roos on nonresidential low-sloped roos; applies to

new and retrot projects over certain size thresholds.

- Georgia Energy

Code revision applicable to cool roos.

- See Energy Code listings underChicago Department o Construction and Permits under local government

portion o the website.

COOL ROOFS DRAFT 23
http://eetd.lbl.gov/HeatIslandhttp://eetd.lbl.gov/HeatIslandhttp://www.ornl.org/http://www.ornl.org/http://www.swenergy.org/casestudies/arizona/tucson_topsc.htmhttp://www.swenergy.org/casestudies/arizona/tucson_topsc.htmhttp://www.pge.com/res/rebates/cool_roof/index.htmlhttp://www.pge.com/res/rebates/cool_roof/index.htmlhttp://www.sce.com/RebatesandSavings/Residential/_Heating+and+Cooling/CoolRoof/http://www.sce.com/RebatesandSavings/Residential/_Heating+and+Cooling/CoolRoof/http://www.sce.com/RebatesandSavings/Residential/_Heating+and+Cooling/CoolRoof/http://www.austinenergy.com/Energy%20Efficiency/Programs/Rebates/Commercial/Commercial%20Energy/buildingEnvelope.htmhttp://www.austinenergy.com/Energy%20Efficiency/Programs/Rebates/Commercial/Commercial%20Energy/buildingEnvelope.htmhttp://www.austinenergy.com/Energy%20Efficiency/Programs/Rebates/Commercial/Commercial%20Energy/buildingEnvelope.htmhttp://egov.cityofchicago.org/http://egov.cityofchicago.org/http://www.epa.gov/heatisland/http://www.epa.gov/heatisland/http://www.ecasavesenergy.org/ses/whiteroof.htmlhttp://www.ecasavesenergy.org/ses/whiteroof.htmlhttp://www.energy.ca.gov/title24/index.htmlhttp://www.energy.ca.gov/title24/index.htmlhttp://rules.sos.state.ga.us/docs/110/11/1/03.pdfhttp://rules.sos.state.ga.us/docs/110/11/1/03.pdfhttp://egov.cityofchicago.org/http://egov.cityofchicago.org/http://egov.cityofchicago.org/http://rules.sos.state.ga.us/docs/110/11/1/03.pdfhttp://www.energy.ca.gov/title24/index.htmlhttp://www.ecasavesenergy.org/ses/whiteroof.htmlhttp://www.epa.gov/heatisland/http://egov.cityofchicago.org/http://www.austinenergy.com/Energy%20Efficiency/Programs/Rebates/Commercial/Commercial%20Energy/buildingEnvelope.htmhttp://www.austinenergy.com/Energy%20Efficiency/Programs/Rebates/Commercial/Commercial%20Energy/buildingEnvelope.htmhttp://www.sce.com/RebatesandSavings/Residential/_Heating+and+Cooling/CoolRoof/http://www.sce.com/RebatesandSavings/Residential/_Heating+and+Cooling/CoolRoof/http://www.pge.com/res/rebates/cool_roof/index.htmlhttp://www.swenergy.org/casestudies/arizona/tucson_topsc.htmhttp://www.ornl.org/http://eetd.lbl.gov/HeatIsland


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Access these calculators on the Web:

ENERGY STAR Calculator:

,

under Roo Products.

ORNL Calculator:

.

For inormation on an eort begun

in 2007 to develop an integrated

EPA/Department o Energy (DOE)

calculator, see: .

The roong calculator is intended to

estimate the savings that a refective roo

can oer to a typical building and to aid

in the decision o whether to choose an

ENERGY STAR-qualied roo product. It is

only one o many tools that can be used in

the decision making process. A more de

tailed building energy simulation would be

needed to estimate savings or a particular

building or calculate specic benet-costratios or a project.

Note that the ENERGY STAR calculator es

timates could underpredict the energy sav

ings rom a cool roo in some cases. This

is because the equations used in the EN

ERGY STAR calculator were derived rom

multiple runs o a DOE building energy

analysis model, which does not consider

the eects o widely varying roo tempera

tures or duct location. These eects include changes in the thermal conductivity

o the insulation, thermal radiation in the

attic or plenum, and conduction gains to

cooling ducts.

ORNL Cool Roo Calculator.This cool

roo calculator is a Web-based tool that

helps estimate the energy and nancial

impacts rom installing cool roos on build

ings with low-sloped roos that do not have

ventilated attics or plenums.

To generate the equations used in this

tool, researchers ran a computer model o

a roo and ceiling assembly over a range

o climates or roos with varying levels o

insulation, solar refectance, and thermal

emittance. This model was calibrated to

emulate heat transer measurements made

on a special roo and ceiling test assembly

at ORNL.39

This calculator requires input on build

ing location (a choice o 235 dierent U.S.

cities is provided); inormation about the

insulation, solar refectance, and thermal

emittance o the proposed roo; and the

cost o energy and eciency o the heating

and cooling systems. The tool provides the

annual cost savings on a square-oot basis

in comparison to a black roo, as well as

annual heating energy savings or penalty,

also in dollars per square oot.

6.2 Roong Programs and Organizations

Table 7 lists a number o programs that

actively promote cool roos or that are cur

rently involved in cool roo research.

http://www.energystar.gov/http://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htmhttp://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htmhttp://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htmhttp://www.govforums.org/e&whttp://www.govforums.org/e&whttp://www.govforums.org/e&whttp://www.govforums.org/e&whttp://www.govforums.org/e&whttp://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htmhttp://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htmhttp://www.energystar.gov/


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Table 7: Cool Roo Programs and Organizations

Program/Organization Role Web Address

Cool Metal Roong Coalition This industry group educates architects,

building owners, speciers, code and stan

dards ofcials, and other stakeholders about

the sustainable, energy-related impacts o

cool metal roong.

Cool Roo Rating Council (CRRC) Created in 1998 as a nonprot, educational

organization, CRRCs members include

manuacturers, utilities, researchers, and

consultants. CRRC maintains a product rating

program and associated product directory.

ENERGY STAR ENERGY STAR is a joint EPA and DOE program

that helps consumers save money and pro

tect the environment through energy-

efcient products and practices. Regardingcool roos, the Web site provides inorma

tion on qualied roong products, industry

partners, and case studies.

National Roong Contractors

Association (NRCA)

This trade association includes roong, roo

deck, and waterproong contractors and

industry-related associate members. It pro

vides technical and saety inormation, news,

and calendars o industry events.

Roo Consultants Institute (RCI) This international, nonprot association

includes proessional roo consultants, archi

tects, and engineers. It hosts trade conventions and develops standards or proessional

qualications.

Roo Coatings Manuacturers As

sociation (RCMA)

RCMA is a national trade association repre

senting the manuacturers o cold-applied

coatings and cements or roong and wa

terproong. It promotes the availability and

adaption o energy-efcient materials.

Single Ply Roong Industry (SPRI) SPRI is a trade organization representing

sheet membrane and component suppli

ers to the commercial roong industry. It

provides inormation about and orums to

discuss industry practices, workorce training,

and other concerns.

COOL ROOFS DRAFT 25
http://www.coolmetalroofing.org/http://www.coolroofs.org/http://www.energystar.gov/http://www.nrca.net/http://www.rci-online.org/http://www.roofcoatings.org/http://www.spri.org/http://www.spri.org/http://www.roofcoatings.org/http://www.rci-online.org/http://www.nrca.net/http://www.energystar.gov/http://www.coolroofs.org/http://www.coolmetalroofing.org/


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Endnotes

1 Rose, L.S., H. Akbari, and H. Taha. 2003. Characterizing the Fabric o the Urban Environment: A

Case Study o Greater Houston, Texas. Paper LBNL-51448. Lawrence Berkeley National Labora

tory, Berkeley, CA.

2 These temperature ranges are compiled rom the ollowing individual reports:

Konopacki, S., L. Gartland, H. Akbari, and I. Rainer. 1998. Demonstration o Energy Savings o

Cool Roos. Paper LBNL-40673. Lawrence Berkeley National Laboratory, Berkeley, CA.

Gartland, L. n.d. Cool Roo Energy Savings Evaluation or City o Tucson.

Miller, W.A., A. Desjarlais, D.S. Parker, and S. Kriner. 2004. Cool Metal Roong Tested

or Energy Eciency and Sustainability. CIB World Building Congress, May 1-7, 2004.

Toronto, Ontario.

Konopacki, S. and H. Akbari. 2001. Measured Energy Savings and Demand Reduction rom

a Refective Roo Membrane on a Large Retail Store in Austin. Paper LBNL-47149. Lawrence

Berkeley National Laboratory, Berkeley, CA.

3 Ibid.

4 Konopacki, S., L. Gartland, H. Akbari, and I. Rainer. 1998. Demonstration o Energy Savings o


5 Rosenzweig, C., W. Solecki, L. Parshall, S. Gan, B. Lynn, R. Goldberg, J. Cox, and S. Hodges.

2006. Mitigating New York Citys Heat Island with Urban Forestry, Living Roos, and Light Sur

aces. Sixth Symposium on the Urban Environment and Forum on Managing our Physical and

Natural Resources, American Meteorological Society. Atlanta, GA.

6 Chen, Allan. Cool Colors, Cool Roos, part 2. Science Beat Berkeley Lab. 27 August 2004. Re

trieved 14 April 2008 rom .

7 Pacic Gas and Electric Company. 2006. Inclusion o Solar Refectance and Thermal Emittance

Prescriptive Requirements or Residential Roos in Title 24. Pacic Gas and Electric Company.Sacramento, CA.

8 Public Interest Energy Research Program. At Home with Cool-Colored Roos. Technical Brie,

CEC-500-2005-164-F111005. Caliornia Energy Commission. Sacramento, CA.

9 Haberl, J., and S. Cho. 2004. Literature Review o Uncertainty o Analysis Methods (Cool Roos),

Report to the Texas Commission on Environmental Quality. Energy Systems Laboratory, Texas

A&M University, College Station, TX.

10 Konopacki, S., L. Gartland, H. Akbari, and L. Rainer. 1998. Demonstration o Energy Savings o


11 Konopacki, S., H. Akbari, M. Pomerantz, S. Gabersek, and L. Gartland. 1997. Cooling Energy

Savings Potential o Light-Colored Roos or Residential and Commercial Buildings in 11 U.S.

Metropolitan Areas. Paper LBNL-39433. Lawrence Berkeley National Laboratory, Berkeley, CA.

12 See the ollowing reports or individual results:

H. Akbari, S. Bretz, J. Hanord, D. Kurn, B. Fishman, H. Taha, and W. Bos. 1993. Monitor

ing Peak Power and Cooling Energy Savings o Shade Trees and White Suraces in the

Sacramento Municipal Utility District (SMUD) Service Area: Data Analysis, Simulations, and

Results. Paper LBNL-34411. Lawrence Berkeley National Laboratory, Berkeley, CA.

Callahan, M., D. Parker, J. Sherwin, and M. Anello. 2000. Demonstrated Energy Savings o

http://www.lbl.gov/Science-Articles/Archive/sb/Aug-2004/3_coolroofs-2.htmlhttp://www.lbl.gov/Science-Articles/Archive/sb/Aug-2004/3_coolroofs-2.htmlhttp://www.lbl.gov/Science-Articles/Archive/sb/Aug-2004/3_coolroofs-2.html


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Eciency Improvements to a Portable Classroom. American Council or an Energy Ecient

Economy. ACEEE Summer Study on Energy Eciency in Buildings. Pacic Grove, CA.

Konopacki, S. and H. Akbari. 2001. Measured Energy Savings and Demand Reduction rom

a Refective Roo Membrane on a Large Retail Store in Austin. Paper LBNL-47149. Lawrence

Berkeley National Laboratory, Berkeley, CA.

Parker, D.S., J.B. Cummings, J.R. Sherwin, T.C. Stedman, and J.E.R. McIlvaine. 1994. Measured Residential Cooling Energy Savings rom Refective Roo Coatings in Florida. ASHRAE

Transactions, Paper 3788. 100(2):36-49.

Parker, D.S., J.R. Sherwin, J.K. Sonne, S.F. Barkaszi. 1996. Demonstration o Cooling Savings

rom Light Colored Roo Suracing in Florida Commercial Buildings: Our Saviors School.

Florida Solar Energy Center, Cocoa, FL.

Parker, D., S.F. Barkaszi, and J.K. Sonne. 1994. Measured Cooling Energy Savings rom Re

fective Roo Coatings in Florida: Phase II Report. Florida Solar Energy Center, Cape Canav

eral, FL.

13 Konopacki, S., H. Akbari, M. Pomerantz, S. Gabersek, and L. Gartland. 1997. Cooling Energy

Savings Potential o Light-Colored Roos or Residential and Commercial Buildings in 11 U.S.

Metropolitan Areas. Paper LBNL-39433. Lawrence Berkeley National Laboratory, Berkeley, CA.14 Konopacki, S., and H. Akbari 2002. Energy Savings or Heat Island Reduction Strategies in Chi

cago and Houston (Including Updates or Baton Rouge, Sacramento, and Salt Lake City). Paper

LBNL-49638. Lawrence Berkeley National Laboratory, Berkeley, CA.

15 Gartland, L. 1998. Roo Coating Evaluation or the Home Base Store in Vacaville, Caliornia.

PositivEnergy, 27. Oakland, CA.

16 Vincent, B., and J. Huang. 1996. Analysis o the Energy Perormances o Cooling Retrots in

Sacramento Public Housing Using Monitored Data and Computer Simulations. Contract No.

500-93-053. Prepared or the Caliornia Energy Commission, Sacramento, CA.

17 Parker, D. 1997. Cool Roos. FSEC-PF-323-97. Rooer Magazine. 17(7).

18 Konopacki, S., H. Akbari, M. Pomerantz, S. Gabersek, and L. Gartland. 1997. Cooling EnergySavings Potential o Light-Colored Roos or Residential and Commercial Buildings in 11 U.S.

Metropolitan Areas. Paper LBNL-39433. Lawrence Berkeley National Laboratory, Berkeley, CA.

19 See Energy Inormation Administration. 2003. Retrieved February 11, 2008, rom . Electricity prices are reported as cents per kilowatt-hour. Natural gas prices

were converted rom dollars per 1,000 cubic eet (28,300 liters) o gas to cents per thousand

Btu (1.1 MJ) based on a conversion actor o 1,021 Btu/cubic oot o gas.

20 Blasnik, M. 2004. Impact Evaluation o the Energy Coordinating Agency o Philadelphias Cool

Homes Pilot Project. M. Blasnik & Associates, Boston, MA.

21 Levinson, R., H. Akbari, S. Konopacki, and S. Bretz. 2002. Inclusion o Cool Roos in Nonresi

dential Title 24 Prescriptive Requirements. Paper LBNL-50451. Lawrence Berkeley National

Laboratory, Berkeley, CA.

22 Mattison, K. 1998. Factors Aecting Roo System Costs. Perspectives. 34 (December). Retrieved 9

October 2007 rom .

23 Levinson, R., H. Akbari, S. Konopacki, and S. Bretz. 2002. Inclusion o Cool Roos in Nonresi

dential Title 24 Prescriptive Requirements. Paper LBNL-50451. Lawrence Berkeley National

Laboratory, Berkeley, CA.

24 Ibid.

COOL ROOFS DRAFT 27
http://www.eia.doe.gov/http://www.eia.doe.gov/http://www.benchmark-inc.com/articles/Perspective%20Articles/issue34a.htmlhttp://www.benchmark-inc.com/articles/Perspective%20Articles/issue34a.htmlhttp://www.eia.doe.gov/http://www.eia.doe.gov/


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25 Pacic Gas and Electric Company. 2006. Inclusion o Solar Refectance and Thermal Emittance Pre

scriptive Requirements or Residential Roos in Title 24. Drat Report, May 17, 2006. Sacramento, CA.

26 See the ollowing study which includes an analysis o annual energy peak demand reductions,

cooling equipment savings, and net present value savings rom expanding Caliornia cool roo

requirements to portions o the residential sector:

Pacic Gas and Electric Company. 2006. Inclusion o Solar Refectance and Thermal Emittance Prescriptive Requirements or Residential Roos in Title 24. Drat Report, May 17,

2006. Sacramento, CA.

27 Bretz, S., and H. Akbari. 1997. Long-Term Perormance o High-Albedo Roo Coatings. Energy &

Buildings. 25(2):159-167.

28 Akbari, H., S. Konopacki, C. Eley, B. Wilcox, M. Van Geem and D. Parker. 1998. Calculations in

Support o SSP90.1 or Refective Roos. Paper LBNL-40260. Lawrence Berkeley National Labora

tory, Berkeley, CA.

29 Akbari, H., S. Konopacki, and D. Parker. 2000. Updates on Revision to ASHRAE Standard 90.2:

Including Roo Refectivity or Residential Buildings. American Council or an Energy Ecient

Economy. ACEEE Summer Study on Energy Eciency in Buildings. Pacic Grove, CA.

30 Konopacki, S., and H. Akbari. 19

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