View
220
Download
0
Embed Size (px)
Citation preview
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
1/31
Reducing Urban Heat IslandsCompendium of Strategies
Cool Roofs
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
2/31
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.
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
3/31
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
4/31
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
5/31
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
6/31
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
7/31
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).
REDUCING URBAN HEAT ISLANDS DRAFT4
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
8/31
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
9/31
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.
REDUCING URBAN HEAT ISLANDS DRAFT6
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
10/31
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/8/9/2019 Reducing Urban Heat Islands: Cool Roofs
11/31
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.
REDUCING URBAN HEAT ISLANDS DRAFT8
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
12/31
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
13/31
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.
REDUCING URBAN HEAT ISLANDS DRAFT10
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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 $3.00 per square oot, including
materials, installation, and reasonable
preparation work. This cost does not in
clude extensive repair work or removaland disposal o existing roo layers.
For either type o cool roo, there canbe a cost premium compared to other
roong products. In terms o dollars
per square oot, the premium ranges
rom zero to 5 or 10 cents or most
products, or rom 10 to 20 cents or a
built-up roo with a cool coating used
in place o smooth asphalt or alumi
num coating. As with any roong job, costs depend
on the local market and actors such as
the size o the job, the number o roo
penetrations or obstacles, and the ease
o access to the roo. These variables
oten outweigh signicantly the dier
ence in costs between various roong
material options.22
REDUCING URBAN HEAT ISLANDS DRAFT12
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
16/31
Table 2: Comparison o Traditional and Cool Roo Options23
Warmer Roo Options Cooler Roo Options
Roo Type Reectance Emittance
Cost
($/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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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
REDUCING URBAN HEAT ISLANDS DRAFT14
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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) --
REDUCING URBAN HEAT ISLANDS DRAFT16
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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/8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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.
REDUCING URBAN HEAT ISLANDS DRAFT18
http://www.coolroofs.org/http://www.coolroofs.org/8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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.
REDUCING URBAN HEAT ISLANDS DRAFT20
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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
8/9/2019 Reducing Urban Heat Islands: Cool Roofs
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.
REDUCING URBAN HEAT ISLANDS DRAFT22
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.html8/9/2019 Reducing Urban Heat Islands: Cool Roofs
26/31
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/HeatIsland8/9/2019 Reducing Urban Heat Islands: Cool Roofs
27/31
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.
REDUCING URBAN HEAT ISLANDS DRAFT24
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/8/9/2019 Reducing Urban Heat Islands: Cool Roofs
28/31
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/8/9/2019 Reducing Urban Heat Islands: Cool Roofs
29/31
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
Cool Roos. Paper LBNL-40673. Lawrence Berkeley National Laboratory, Berkeley, CA.
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
Cool Roos. Paper LBNL-40673. Lawrence Berkeley National Laboratory, Berkeley, CA.
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
REDUCING URBAN HEAT ISLANDS DRAFT26
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.html8/9/2019 Reducing Urban Heat Islands: Cool Roofs
30/31
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/8/9/2019 Reducing Urban Heat Islands: Cool Roofs
31/31
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