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Benefits  > Heat Island Reduction
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Cities and urban areas are 3 to 8 °F (2 to 4°C) warmer than surrounding areas due to the heat island effect as shown in Fig. 1. This temperature difference is attributed to more buildings and pavements that have taken the place of trees and vegetation. Trees provide shade that reduces temperatures at the surface. Trees and vegetation give off water (transpiration) that evaporates and cools their surfaces and the surrounding air. Research has shown that the average temperature of Los Angeles has risen steadily over the past half century, and is now 6 to 7°F (3 to 4°C) warmer than 50 years ago.
 
sketch of urban heat island profile
Urban Heat Island Profile [LBNL website http://eetd.lbl.gov/HeatIsland/]
how
Concrete provides reflective surfaces that minimize the urban heat island effect. Urban heat islands are primarily attributed to horizontal surfaces such as roofs and pavements that absorb solar radiation. In this context, pavements include roads, parking lots, driveways and sidewalks. Where paved surfaces are required, materials with higher solar reflectance (albedo), such as concrete, will reduce the heat island effect, save energy by reducing the demand for air conditioning, and improve air quality.
 
The daily temperature rise on hot days results in an increase in the peak energy consumption in all major cities due to an increase in the air conditioning load. Smog levels have also been correlated to temperature rise. Thus, as the temperature of urban areas increases, so does the probability of smog and pollution. In Los Angeles, the probability of smog increases by 3% with every degree F (5% with every degree C) of temperature rise.
 
What is Albedo?

Albedo, which in this case is synonymous with solar reflectance, is the ratio of the amount of solar radiation reflected from a surface to the total amount reaching that surface. The solar radiation reaching an object on earth includes visible and ultraviolet light and infrared radiation. Ordinary portland cement concrete generally has a solar reflectance of approximately 0.35 to 0.45 although values can vary. The solar reflectance of new concrete is greater when the surface reflectance of the sand and cementitious materials in the concrete are greater. Surface finishing techniques and drying time also affect solar reflectance. Solar reflectance is most commonly measured using a solar reflectometer (ASTM C1549) or a pyranometer (ASTM E1918).
 
A composite index called the solar reflectance index (SRI) is used by the U.S. Green Building Council and others to estimate how hot a surface will get when exposed to full sun. The temperature of a surface depends on the surface’s reflectance and emittance, as well as solar radiation. The Solar Reflectance Index (SRI) is used to determine the effect of the reflectance and emittance on the surface temperature, and varies from 100 for a standard white surface to zero for a standard black surface. The SRI is calculated using ASTM E1980, “Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surfaces.” Materials with the highest SRI are the coolest and the most appropriate choice for mitigating the heat island effect.

Emittance, also known as emissivity of a surface, is a measure of how well a surface emits or releases heat. It is a value between 0 and 1. Highly polished aluminum has an emittance less than 0.1. A black non-metallic surface, on the other hand, has an emittance greater then 0.9. However, most opaque non-metallic materials encountered in the built environment (such as concrete, masonry, and wood) have an emittance between 0.85 and 0.95, and a value of 0.90 is usually assumed(6). Further, for these materials, SRI is mostly a function of solar reflectance. In other words, a building material with a high solar reflectance will probably also have a high SRI.

Table 1 shows the reflectance, emittance and SRI of some common building materials.

Table 1. Solar reflectance (albedo), Emittance, and Solar Reflective Index (SRI) of select material surfaces[1],[2],[3],[4]

Material surface

Solar Reflectance*

Emittance

SRI*

Black acrylic paint

0.05

0.9

0

New asphalt

0.05

0.9

0

Aged asphalt

0.1

0.9

6

“White” asphalt shingle

0.21

0.91

21

Aged concrete

0.2 to 0.3

0.9

19 to 32

New concrete (ordinary)

0.35 to 0.45

0.9

38 to 52

New white portland cement concrete

0.7 to 0.8

0.9

86 to 100

White acrylic paint

0.8

0.9

100

*See also the section on LEED below.

HOW does a Project Obtain LEED® Credit for Reducing Temperature in Heat Islands?
 
Trees and light colored surfaces such as concrete help lessen the heat island effect in cities.  PCA No. 67548.
Concrete surfaces can earn a LEED for New Construction and Major Renovation (LEED-NC version 2.2) credit through Sustainable Sites Credit 7.1: “Heat Island Effect, Non-Roof”. The intent of this credit is to reduce the heat island effect. The intent can be met if materials that stay cool in sunlight are used on at least half of the site’s non-roof impervious surfaces, such as roads, sidewalks, courtyards, and parking lots (hardscape). The material’s solar reflectance index (SRI) must be at least 29. Where paved surfaces are required, using materials with higher SRI will reduce the heat island effect, consequently saving energy by reducing demand for air conditioning, and improve air quality. Concrete and concrete pavers are ideally suited to meet this requirement. Ordinary portland cement concrete has an SRI in the range of 38 to 52, although it can vary. However, unless it is actually measured, LEED allows an SRI of 35 for ordinary portland cement concrete (see the LEED-NC Reference Guide). New concrete made with white portland cement has an SRI of 86 according to the Reference Guide.
 
Other options include placing a minimum of 50% of parking spaces undercover (such as underground, under deck, under roof, and under building); using an open-grid pavement system with more than 50% perviousness; or provide shade within 5 years of occupancy.
 
 Sustainable Sites Credit 7.2: "Heat Island Effect: Roof" can also be achieved with concrete, specifically white cement tiles, with an SRI of 90 in the Reference Guide.  The threshold for the roof credit is 75% of the roof with an SRI of 78 or better for low-slope and 29 or better for steep-slope. Other compliance options for the roof credit are 50% green roof or a combination of green roof and high SRI roofing materials.  Concrete, particularly if waterproof, is an excellent substrate for a green roof because of its strength and durability. 


[1] Levinson, Ronnen and Akbari, Hashem, “Effects of Composition and Exposure on the Solar Reflectance of Portland Cement Concrete,” Lawrence Berkeley National Laboratory, Publication No. LBNL-48334, 2001, 39 pages.

[2] Pomerantz, M., Pon, B., and Akbari, H., “The Effect of Pavements’ Temperatures on Air Temperatures in Large Cities,” Lawrence Berkeley National Laboratory, Publication No. LBNL-43442, 2000, 20 pages.

[3] Berdahl, P. and Bretz, S, "Spectral Solar Reflectance of Various Roof Materials", Cool Building and Paving Materials Workshop, Gaithersburg, Maryland, July 1994 14 pages.

[4]Pomerantz, M., Akbari, H., Chang, S.C., Levinson, R., and Pon, B., “Examples of Cooler Reflective Streets for Urban Heat-Island Mitigation: Portland Cement Concrete and Chip Seals,” Lawrence Berkeley National Laboratory, Publication No. LBNL-49283, 2002, 24 pages.

BOOKMARK
Resources
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 Pervious Concrete
Concrete Technology, August, 2007
A properly designed pervious concrete pavement system can reduce the environmental impact often associated with development. This overview discusses the hydrologic design of pervious concrete, both passive and active mitigation systems and the important consideration in design for storms. The article includes a link to a publication on pervious paving design as well.
Located at BookstoreAccelerated Pavement Testing to Evaluate UTW Load-Carrying Capacity
This special report describes the accelerated pavement testing of ultra-thin whitetopping (UTW) undertaken by the Federal Highway Administration at their accelerated loading facility (ALF) in McLean, Virginia. The UTW pavement sections were placed in 1998 atop existing asphalt sections that had been previously loaded by the ALF. The eight pavement sections were loaded by the facility, and five of the eight lanes showed little or no distress as a result. Conclusions indicate that the load carrying capacity of UTW is sufficient for its intended uses, including streets, local roadways, general aviation pavements, bus lanes, turning lanes, and ramps.
Located at BookstoreAirfield Pavement Design with Concrete Pavers (Canadian Edition) (1994)
Interlocking Concrete Pavement Institute, #76505, 80 pages
Regular $36.00 (Member $18.00) Transport Canada approved design method for aircraft parking area, taxiways and turning area. Follows Canadian design procedure based on critical aircraft loads and the McLeod method.
Located at BookstoreAirfield Pavement Design with Concrete Pavers (US Edition) (1995)
Interlocking Concrete Pavement Institute, #76504, 100 pages
Federal Aviation Administration (FAA) approved design method for aircraft parking, taxiways and turning areas. Follows FAA design procedure based on critical aircraft loads. This publication is available for a fee from the Interlocking Concrete Pavement Institute.
Located at BookstoreBackyards & Boulevards (2004)
Interlocking Concrete Pavement Institute, #75300, 192 pages
Available for $25 members, $29.95 non-member. The endless possibilities for residential, commercial and municipal applications fill this book with over 300 pictures. They demonstrate how paver patterns, colors and textures enliven backyard patios, plazas, shopping centers, recreation facilites and residential and commercial districts. This book is a source for design inspiration for manufacturers, contractors and design professionals. This publication is availbale form the Interlocking Concrete Pavement Institue.
Located at BookstoreBob Harris' Guide to Stamped Concrete (2004)
Bob Harris, Decorative Concrete Institute, Item Code LT284, 144 pages
Available for $45. The guide covers topics of vital importance for anyone planning to stamp concrete, including: - Nine sources for stamping design ideas - Maximizing your profits by knowing what to charge - Concrete mix considerations for stamping concrete - Site conditions affecting stamped concrete work and how to prepare or avoid them - How to prepare concrete for stamping, including tips for striking off and finishing - Three important steps to applying color hardener - Tools that are essential for successful stamping - How and when to start stamping - Important issues to avoid when stamping - Fixing minor flaws in stamped concrete work - Effective techniques for the application of sealers - 10 ways to promote and sell your stamped concrete work - How to distinguish your stamped concrete work from competitors
Located at BookstoreComplete Business Manual for Concrete Paver Contractors (1998)
Charles Vander Kooi, Interlocking Concrete Pavement Institute, #75100, 240 pages
Available for $60 member, $100 non-member. A comprehensive guide on estimating, bidding, people and company management and planning. This book has the keys to business success for all sizes of concrete paver contracting companies. This publication is available for a fee from Interlocking Concrete Pavement Institue's bookstore.
Located at BookstoreFinishing Concrete with Color and Texture (2004)
Steven H. Kosmatka and Terry C. Collins, Portland Cement Association, Item Code PA124, 72 pages
Available for $35. This publication is a basic guide for planning and constructing decorative concrete surfaces on concrete slabs. While intended primarily for concrete contractors, it also will be useful to concrete finishers, concrete finishers apprentices, homebuilders, general contractors, architects, engineers, landscape architects, homeowners, vocational education students, specification writers, inspectors, and many others.
Located at BookstoreInfluence of Pavement Reflectance on Lighting for Parking Lots (2005)
Adrian, W. and Jobanputra, R. Item Code: SN2458
Available for free. This investigation has compared the lighting performance of concrete and asphalt surfaces of parking lots. The resulting amount of energy saved for a typical parking lot lighting system was attained for equivalent average surface luminances. Equivalent average surfaces were compared in two ways: by modifying lamp power and by reducing the number of lighting poles.
Located at BookstorePatios, Driveways, and Plazas (2002)
Interlocking Concrete Pavement Institute, #75200, 192 pages
Available for $25 member, $29.95 non-member. Concrete pavers are one of the hottest pavements around homes, commercial buildings and urban spaces. Designers know that the selection of pavement patterns and colors have a big influence on the character of these places. In this book, you'll learn the design vocabulary of basic paving patterns and progress to more intricate variations. Each of the 300+ color photos demonstrates how specific patterns, colors and textures enhance every outdoor environment--from the smallest backyard patio to the grandest urban plaza. Some of the best projects from across North America illustrate this book. Written for landscape architects, architects, contractors, and homeowners alike, this is the design handbook for concrete pavers.
Located at BookstorePermeable Interlocking Concrete Pavements (2002)
Interlocking Concrete Pavement Institute, #76602, 54 pages
Available for $10 member, $20 non-member. A guide for design specification, construction and maintenance of pervious pavement made with concrete pavers. Guides designers on using this best management practice for control of stormwater runoff and nonpoint source water pollution.
Located at BookstorePervious Concrete Pavements (2004)
Paul D. Tennis, Michael L. Leming, and David J. Akers, Portland Cement Association, Item Code EB302, 36 pages
Available for $25. Pervious concrete as a paving material has seen renewed interest due to its ability to allow water to flow through itself to recharge groundwater and minimize stormwater runoff. This introduction to pervious concrete pavements reviews its applications and engineering properties, including environmental benefits, structural properties, and durability. Both hydraulic and structural design of pervious concrete pavements are discussed, as well as construction techniques.
Located at BookstorePort and Industrial Pavement Design with Concrete Pavers (1997)
Interlocking Concrete Pavement Institute, #76506, 101 pages
Available for $18 member, $36 non-member. Second Edition Port pavement design based on finite-element modeling and adapted from the British Ports Association. Sample specifications, examples, and design details for new and overlay design for industrial, bulk and container facilities.
Located at BookstorePortland Cement Concrete Overlays - State of the Technology Synthesis (2002)
American Concrete Pavement Association, Product Code SP045P, 188 pages
Available for $5. Link goes to bookstore page, search by product code. This report, produced by the Federal Highway Administration (FHWA), presents the latest information on the design, construction, and performance of portland cement concrete (PCC) overlays. Bonded, unbonded, whitetopping, and ultra-thin whitetopping overlays are covered in this synthesis of the current state of the technology. This comprehensive book is a must-have for those interested in concrete pavement overlay design and construction.
Located at BookstoreRepair of Ultra-thin Whitetopping (2000)
American Concrete Pavement Association, Product Code PA397P, 4 pages
This document is available for $6 from American Concrete Pavement Association, search by product code at bookstore. This semi-technical brochure outlines the requirements and steps to repairing ultra-thin whitetopping overlays. Full-color photographs visually demonstrate each step.
Located at BookstoreThe Patio Portfolio (2004)
Interlocking Concrete Pavement Institute, #75400, 128 pages
This publication is available for $16.95 members, 19.95 regular. This award-winning publication includes over 200 photos of the finest patio projects designed to inspire design professionals, contractors and homeowners.
Located at BookstoreWhitetopping State of the Practice
American Concrete Pavement Association, Product code EB210P, 70 pages
This document is available for $25 from the American Concrete Pavement Association, search by product code. Best-selling engineering manual includes comprehensive coverage of all aspects of concrete overlays on existing asphalt pavement. It includes information on the benefits, history, performance, design practices, and construction of all types of whitetopping. A special chapter discusses Ultra-Thin Whitetopping (UTW), including an interim procedure for determining the load-carrying capacity of UTW based on research and performance surveys.
Download DocumentAchieving LEED® Credits with Segmental Concrete Pavements—Part 1 (2006)
Rob Burek, P.Eng.-ICPI Director of Engineering, Interlocking Concrete Pavement Magazine, May, 2006
This 3 page article reviewed the U.S. and Canadian Green Building Councils LEED® versions for new construction. It provides the why behind LEED®, i.e. a project checklist used voluntarily that aims to reduce construction, energy and water-related operating costs while reducing environmental impacts. It also explains how permeable interlocking concrete pavement can contribute LEED® points through Sustainable Sites (SS) via stormwater management. In addition SS points can be earned through reducing urban heat island on parking lots and roofs, by reducing construction waste, reusing pavers and by using recycled materials, using materials made from within the region as well as proposing innovative design and using durable materials. Applications: Stormwater Design and Management, Heat Island Reduction, Recycling, Regional Manufacturing, Waste Management.
Download DocumentAchieving LEED® Credits with Segmental Concrete Pavements—Part 2 (2006)
Rob Burak, P.Eng.-ICPA Director of Engineering, Interlocking Concrete Pavement Magazine, August, 2006
This 4 page article continues from the May issue on how LEED® credits can be earned under the five principal categories. It details how points Sustainable Sites (SS) can be earned through heat island effect both in non roof and roof, material and resources, by reducing construction waste, resource reuse, by using recycled materials, using materials manufactured within the region as well as incorporating innovative improvements in building materials and design and durable materials. Applications: Heat Island Effect, Materials and Resources, Construction Waste Management, Resource Reuse, Recycled Content, Regional Materials, Innovation and Design Process, Durable Materials.
Download DocumentAlbedo: A Measure of Pavement Surface Reflectance (2002)
American Concrete Pavement Association, 2 pages
Brochure describing albedo and the impact of pavement material selection on energy consumption, cool communities, and cost savings. This brochure is available as a free download from the American Concrete Pavement Association.
Download DocumentConcrete in Practice No. 38 - Pervious Concrete (2004)
National Ready Mixed Concrete Association, 2 pages.
Available for free. Concrete In Practice-Pervious Concrete is a one-page information sheets on important technical topics, written in a non-technical "What, Why and How?" format.
Download DocumentFreeze Thaw Resistance of Pervious Concrete (2004)
National Ready Mixed Concrete Association, 17 pages
Available for free. There have been several pervious concrete pavement projects in dry and wet freeze areas demonstrating good field performance over several years. Recommendations for successful performance of pervious concrete pavements under the various freeze-thaw conditions have been provided. There is limited experience of performance of pervious concrete pavements in hard wet freeze areas. Therefore, in such areas utmost care must be taken. Pervious pavements should be placed by an experienced installer and the pavement structure and surrounding details should be designed to accommodate the anticipated water flow and drainage requirements.
Download DocumentPervious Concrete Mixtures and Properties (2004)
Portland Cement Association, CT043, 8 pages
Available for free. Pervious concrete is ideally suited as a solution to stormwater management issues with added environmental benefits. The large void content designed into this specialty concrete allows water to pass through rapidly, minimizing runoff and recharging groundwater supplies. Also known as permeable concrete, porous concrete, gap-graded concrete, no-fines concrete, and enhanced porosity concrete, pervious concrete can be used in a wide range of applications, although its primary use is in pavements.
Download DocumentPervious Concrete Pavement: A Win-Win System (2003)
Dan Brown, P.E., Portland Cement Association, CT032, 9 pages
Available for free. Use of Pervious Concrete Pavements Helps Owners and the Environment.
Download DocumentShining a Light on Cool Communities (1998)
Environmental Council of Concrete Organizations, #EV 19, 4 pages
Available for free. Research shows that use of light- and heat-reflective concrete-based materials, along with careful planting of trees, could lower summer temperatures in some cities by as much as 5°F. This four-page bulletin presents an overview of this concept.
Download DocumentUnderstanding Pervious Concrete (2005)
Dan Huffman, Construction Specifier Institute, December 2005, 9 pages
Available for free. While pervious concrete pavement has been around for more than 20 years, it has only recently garnered much attention due to increasingly stringent stormwater management guidelines that now position the product as a sustainable building material. Pervious concrete provides the potential for environmentally responsible site use and lowered construction costs in projects ranging from a simple sidewalks, driveways and patios, to major pedestrian plazas and full-blown multi-acre parking lots for national commercial big box builders.
Download DocumentUnique Whitetopping Approach Offers Strength and Durability in Wyoming (2004)
Portland Cement Association, #PL612, 2 pages
Available for free. This 2-page case study highlights the reconstruction of a deteriorated asphalt street in Sheridan, WY. The process included the use of full-depth reclamation (FDR) with cement for the base and ultra-thin whitetoppping (UTW) for the surface. Pavement design called for 3-1/2 inches of UTW with control joints sawn in a four-foot grid over eight inches of an FDR base. Tests performed after construction showed the cement-stabilized FDR base with a 28-day compressive strength of 320 psi and a 28-day concrete compressive strength of 5,250 psi. After a year of traffic, the reconstructed street is performing well, and the city is pleased with the results.
Located at External Web SiteAmerican Coal Ash Association (2006)
A website dealing with the use of coal ash in concrete products.
Located at External Web SiteChanges In Store (2006)
Wal-Mart showcases green concrete technologies at its store in Texas.
This 4 page article was originally featured in the May 2006 edition of Concrete Producer Magazine, by Hanley Wood. Wal-Mart testing a range of green strategies at this prototype store in McKinney, TX. Along with other green strategies, concrete was used as interior finish flooring, reducing VOC's and maintenance, and pervious pavement in the parking area to improve ground water quality and quantity.
Located at External Web SiteConcrete's Contrubition to Sustainable Development
Concrete is the most widely used building material on earth. It has a 2, 000 year track record ofhelping build the Roman Empire to building today's modern societies. As a result ofits versatility, beauty, strength,·and durability, concrete is used in most types ofconstruction, including homes, buildings, roads, bridges, airports, subways, and water resource structures. And with today's heightened awareness and demandfor sustainable construction, concrete performs well when compared to other building materials. Concrete is a sustainable building material due to its many eco{riendly features. The production ofconcrete is resource efficient and the ingredients require little processing. Most materials for concrete are acquired and manufactured locally which minimizes transportation energy. Concrete building systems combine insulation with high thermal mass and low air infiltration to make homes and buildings more energy efficient. Concrete has a long service life for buildings and transportation infrastructure, thereby increasing the period between reconstruction, repair, and maintenance and the associated environmental impact. Concrete, when used as pavement or exterior cladding, helps minimize the urban heat island effect, thus reducing the energy required to heat and cool our homes and buildings. Concrete incorporates recycled industrial byproducts such as fly ash, slag, and silica fume that helps reduce embodied energy, carbon footprint, and waste.
Located at External Web SiteEnvironmental and Cost Benefits of High Albedo Concrete
By Erin Ashley, PhD, LEED AP, Director of Codes and Sustainability, NRMCA
Located at External Web SiteExpanded Shale, Clay, and Slate Institute
Resource for information on structural lightweight aggregate that can be used in greenroof construction
Located at External Web SiteGreen Roofs for Healthy Cities (2005)
Green Roof Industry Association
Located at External Web SiteGreenroofs Information - Concrete Advantages for Green Roofs (2005)
National Ready Mixed Concrete Association
Information source for areas on waterproof concrete for use in greenroofs.
Located at External Web SiteInterlocking Concrete Pavement Institute
Association website include design ideas and specifications for numerous applications.
Located at External Web SiteNational Center of Excellence SMART Materials Program
The National Center of Excellence on SMART Materials is a joint U.S. EPA - Arizona State University partnership formed to bring together researchers of various disciplines in developing the next generation of urban materials to reduce the dependence on non-renewable energy and adverse impacts to the urban climate. The National Center of Excellence will be the leading national research and outreach laboratory in supporting regional governments and industry in meeting the needs of rapid urbanization and infrastructure.
Located at External Web SitePavement - Concrete Parking Website
National Ready Mixed Concrete Association
This link takes you to the environmental benefits section of ConcreteParking.org, where you can learn about the range of technology to reduce storm water problems and urban heat island effects.
Located at External Web SiteReflectivity of Concrete Pavements: An Annotated Bibliography
The reflectivity, or reflectance, of concrete pavements is one of its many important benefits, providing increased safety on our roads and energy reduction due to its lower lighting requirements. This bibliography is a compilation of references to research studies, industry journal articles, and conference papers on this timely and critical topic. Summaries are included, as well as Web links to the full-text documents.
Located at External Web SiteSafe for All Seasons
American Concrete Pavement Association
Available for free. This executive level brochure in the ACPA "Safe for All Seasons" series highlights the benefits and role concrete pavement plays in mitigating urban heat island effects and energy cost savings. Contact rjolly@pavement.com for copies from this series.
Located at External Web SiteSilica Fume Association (2006)
An industry association website.
Located at External Web SiteSlag Cement Association (2006)
An industry resource website dealing with slag cement.
Located at External Web SiteSolar Reflectance of Concretes for LEED Sustainable Sites Credit: Heat Island Effect
by Medgar L. Marceau and Martha G. VanGeem
This report presents the results of solar reflectance testing on 135 concrete specimens from 45 concrete mixes, representing a broad range of concretes. This testing determined which combinations of concrete constituents meet the solar reflectance index requirements in the Leadership in Energy and Environmental Design for New Construction (LEED-NC) Sustainable Sites credit for reducing the heat island effect. All concretes in this study had average solar reflectances of at least 0.30 (corresponding to an SRI of at least 29), and therefore meet the requirements of LEED-NC SS 7.1. These concretes also meet the requirements for steep-sloped roofs in LEED-NC SS 7.2. The lowest solar reflectances were from concretes composed of dark gray fly ash. The solar reflectance of the cement had more effect on the solar reflectance of the concrete than any other constituent material. The solar reflectance of the supplementary cementitious material had the second greatest effect.
Located at External Web SiteUtah Cool Communities Presentation
American Concrete Pavement Association
A Powerpoint presentation at the 1st Annual ACPA Utah Chapter Workshop made by the Utah Department of Energy. Contact rjolly@pavement.com for a free copy of this presentation.