RoofViews

Building Science

Six Truths About Cool Roofs

By GAF Roof Views

June 28, 2021

house with a grey hat and red scarf wrapped around it

Cool roofs can help save you money on energy bills* in the North as well as the South. Here are some cool truths to ponder when planning a new roof.*

TRUTH 1: It's All About Reflectivity

A cool roof reflects the sun's rays away from the roof, helping to reduce rooftop temperatures. While a sunlight-absorbing black roof can reach up to 190°F in the summer, a reflective roof's temperature can be as much as 55°F lower. Dark surfaces also contribute to the urban heat island effect. (SOURCE: heatisland.lbl.gov/coolscience/cool-roofs)

A cool roof reflects away the sun's rays, unlike a dark roof which absorbs them and transfers heat to the building below.

About Heating & Cooling Degree Days:

These units of measure describe how far the average daily temperature varies from a baseline of 65°F. Temperatures greater than 65°F are cooling-degree days, because we need to cool the environment back to 65°F. Heating-degree days occur when the temperature falls below 65°F.

TRUTH 2: On Average, Electricity Costs Up to 4 Times More, Per BTU, Than Natural Gas

If your building uses electric air conditioning and natural gas heat, a cool reflective roof can help lower your cooling costs* no matter where you are in the continental United States (including Northern States) by reducing the amount of air conditioning needed.

On average, electricity costs up to 4 times more, per BTU, than natural gas. Not only is electricity more expensive than gas, but the rate structures are more complex. Seemingly small increases in electricity use can result in large additional costs due to the compounding effects of time of demand charges based on a few peak minutes of electricity usage during each billing period.

How much could you be saving on energy bills? Find out by trying out our CREST energy calculator.

What are "Demand Charges?"

Simply put, demand charges are the immediate usage put on your energy system. Some electric companies charge commercial and industrial buildings a demand charge penalty based on a few peak minutes of electricity usage during each billing period. Buildings that use the most electricity at one time often get charged the largest penalty, which can be up to 30 -70% of their total electricity bill. Air conditioners, by their nature, surge electricity demand at peak times of the day. Cool roofs can help reduce the air conditioning needed by your building by eliminating the extra heat that would be absorbed by a black roof.

TRUTH 3: Dark Roofs Increase the Need for Air Conditioning

Dark roofs not only drive up monthly electricity-consumption costs, they can significantly increase demand charges as well. Less demand can mean less money spent to cool the building.*

TRUTH 4: A Black Roof Covered in Snow is White

Your roof's potential impact on building energy usage is based on the amount of sunlight reaching it, not on the ambient temperature. So even in regions with more "heating degree days" than "cooling degree days" a reflective cool roof can offset more hours of sunlight in summer than a dark roof can absorb to heat the building in winter; almost twice as many at the solstices. And, of course, during those long winter nights, sunlight is having no effect on your roof at all. Add to that the fact that a dark roof covered in snow is, effectively, a white reflective roof. A snow-covered black roof reflects the sun's rays but in the summer, it can become a heat-absorbing sponge.

Truth 5: A Properly Designed Roof Reduces the Risk of Condensation

A properly designed roof can offset condensation in a variety of ways, including using multiple layers of insulation with staggered joints, installing GAF SA Vapor Retarder, or installing a fully adhered system, to just name just a few options.

Truth 6: Cool Roofs are Changing the Roofing Industry

Commercial buildings are benefiting from cool roof savings throughout the USA, even in Northern climates, and that is fundamentally shifting the roofing marketplace. For example, EPDM was the most popular single-ply membrane in the industry in 2003. Today, TPO makes up over 50% of the single-ply market.

GAF offers a wide range of cool roofing technologies including:

Single-Ply — available in both TPO and PVC, single-ply membranes are among the most commonly installed roofing technologies due to the speed of installation and the variety of systems available.

Asphaltic — available in BUR, APP, and SBS, asphaltic systems are great, time-tested multi-ply systems that can be installed in a variety of systems.

Coatings — available in acrylics, silicones, urethanes, PMMAs, and PVDFs, the GAF line of coatings can preserve and restore existing roofs.

For more information on maintenance plans, guarantee extension details, or to be connected with a GAF maintenance professional, please visit our building owner and property manager resources page.



*Energy cost savings are not guaranteed and the amount of savings may vary based on climate zone, utility rates, radiative properties of roofing products, insulation levels, HVAC equipment efficiency, and other factors.

About the Author

More homes and businesses in the U.S. are protected by a GAF roof than by any other product. We are the leading roofing manufacturer in North America, with plants strategically located across the U.S. As a Standard Industries company, GAF is part of the largest roofing and waterproofing business in the world.

Related Articles

A colorful basketball court.
In Your Community

Helping to Mitigate Urban Heat Islands with GAF Streetbond Pavement Coatings

Extreme heat has been the greatest weather-related cause of death in the US for the last 30 years. In fact, between 2010 and 2020, roughly 12,000 Americans died from extreme heat, with Native American and Black communities disproportionately affected. Around the globe, excess heat collects in urban areas and can contribute to increased heat-related death and illness, diminished quality of life, and reduced economic opportunities.One example of this urban heat is Los Angeles's Pacoima neighborhood. During days of extreme temperatures, Pacoima had seven times the number of excess heat emergency room visits (19,000 between 2009 and 2018) compared with nearby Santa Monica, an affluent community of similar size, according to Bloomberg.Economic sectors, such as tourism and local businesses, also feel the effects of urban heat. Pacoima food truck vendor Jennifer Ramirez told Bloomberg she couldn't start work until outdoor and street temperatures cooled. Otherwise, her food truck generator could blow out.Fortunately, cooling strategies are now available and being used in initiatives like the GAF Cool Community Project to help mitigate urban heat.Understanding Heat IslandsYou can envision heat islands as heat-saturated sponges spread out across vast, shimmering urban spaces. These "islands" tend to have minimal shady vegetation, so their blacktop and hard surfaces—such as pavements, parking lots, concrete recreation areas, and roofs—absorb and retain the sun's heat well into the evening. Temperatures in urban heat islands can often be 15°F to 20°F hotter than in equivalent vegetated areas.In technical terms, darker, tarmac-covered surfaces have a "low albedo" effect, which describes the ability to reflect and diffuse the sun's rays back to the upper atmosphere. Meanwhile, reflective, snow-covered regions such as the Arctic have "high albedo." Areas with low albedo are at greater risk of experiencing increased heat retention.Densely packed buildings compound a low albedo effect by preventing cooling breezes from lowering temperatures. To top it off, heat islands can trap waste heat from cars, air conditioners, and other heat-emitting devices—exacerbating the effects. In terms of detrimental environmental impacts, this is the perfect, overheated, storm.Shifting from Heat Islands to Cool CommunitiesThe GAF Cool Community Project addresses the complex issue of urban heat with a simple solution: Take a hot, sun-exposed community with an abundance of heat-retaining surfaces. Then, apply colorful, solar-reflective coating to its streets and public hardscaping—such as GAF StreetBond® pavement coatings with Invisible Shade™, which Time magazine named one of the Best Inventions of 2022.The result? Cooler surfaces and ambient air temperatures.Making Progress on Cooling PacoimaLA's Pacoima neighborhood is one example of a community hit hard by heat. A true urban heat island, it has consistently been one of the city's hottest areas. On one summer afternoon in 2022, Bloomberg reported a pavement temperature of 127°F at noon. Just one hour later, it had risen to 141.8°F.Many of Pacoima's residents are in lower-income brackets and live in spaces that haven't been fully optimized to mitigate heat island effects. So, combatting the heat became a priority for local officials and organizations. Melanie Torres, community organizer with Pacoima Beautiful, said that "the cooling solutions that were brought here to Pacoima were actually very impactful to our community." Torres shared, "it definitely cooled things down, but we definitely did need the educational aspect —beginning the discussion of climate exchange and what extreme heat is, and how we can create solutions to combat it."With resources and support from GAF and non-profit partners, more than 700,000 square feet worth of streets, parking lots, and other hardscapes were coated with StreetBond® over a contiguous 10-block area. Attractive, colorful solar-reflective materials cover the park and playground areas, and blue and white coatings brighten the public basketball court. The formerly dark streets are now a cool gray-blue.According to Miguel Angel Luna, president of Urban Semillas, Pacoima residents are right "on the front line of climate change." Urban Semillas is an LA-based social and environmental justice consultancy working with GAF on the Cool Community Project.Achieving Positive Results in PacoimaOver the past year, Cool Community Project members monitored pavement and air temperatures using sensors, satellite technology, and drones. Findings from the past 12 months of observation have shown a positive impact on the Pacoima community:Ambient air temperature (Surface temperatures have been reduced by an average of 10°F during the daytime on sunny days.The second phase of the project includes applying pavement coatings to an additional 500,000 square feet of streets and introducing a new cooling technology on select residences—Timberline® CS Shingles. These shingles are made with a highly reflective material that can help reduce attic temperatures and air conditioning costs.In addition to heat reduction and urban beautification, GAF StreetBond® can help preserve pavement. Longer-lasting pavement can save cities time, money, and resources while giving them another tool to help mitigate the impacts of climate change. This is just another way GAF is looking to strengthen communities from the ground up.Through this project, GAF and its partners aim to improve the lives of the roughly 2,000 people living within the project area of Pacoima. They're accomplishing this by taking what Jeff Terry, GAF vice president of sustainability, describes as a "complete community approach," which involves residents and local organizations coming together to create a model for cities around the world.Reducing Temperatures at HomeWhether urban or rural, all communities can use technology to help reduce indoor and outdoor temperatures. Some cooling strategies that can be effective across cities or in your own home include:Cool SurfacesSurfaces treated with solar-reflective coatings can help reduce heat absorption and lower street and ambient air temperatures. Plus, products such as StreetBond® come in a range of colors to highlight urban areas and preserve pavement.Cool RoofsSolar reflective shingles like Timberline® CS Shingles may save homeowners an average of 7% to 15% on their total cooling costs.* This cooling technology can minimize a building's solar heat gain by reflecting incoming sun rays and reemitting the absorbed energy.Ready to get started in your neighborhood? Check out the inspiring community improvement projects at streetbond.com. (A division of GAF, StreetBond® offers the same quality and reliability customers have come to rely on from North America's largest roofing and waterproofing manufacturer.)*Potential for savings depends on various factors including, but not limited to, climate zone, utility rates, location, and HVAC equipment efficiency.

By Authors Annie Crawford

October 20, 2023

Asphalt roof shingles with sun beaming on the roof
Your Home

How Hot Does a Roof Get in the Summer?

Exactly how hot does a roof get in the summer? According to the US Department of Energy, traditional darker asphalt shingle roofs can get up to 150°F on a sunny summer day. And prolonged exposure to high heat like this can damage your roof.Four Potential Effects of Summer Weather on Your RoofHere are four common ways hot summer weather can adversely affect your roof system:1. High HeatOver time, high heat can damage roofing materials.2. Ultraviolet LightUV light shines down on your roof on both sunny and cloudy days during the summer. Over time it can cause materials to deteriorate and diminish the amount of protection your roof shingles ultimately provide, leaving your roof vulnerable to leaks.3. HumiditySummer's high humidity can also damage your roof by creating condensation that collects under the shingles. If left unaddressed, this moisture can cause water damage, leaks, or mold growth.4. Thermal ShockThermal shock occurs when high temperatures during the day are followed by quickly cooling temperatures at night. This temperature swing can cause roofs to expand and contract rapidly, weakening the roof's integrity.How to Reduce the Risk of Heat Damage to Your RoofHere are a few strategies to help reduce the risk of heat damage:Ventilate the AtticA properly balanced attic ventilation system helps damaging heat and moisture to escape. Make sure you have the proper amount of ventilation needed to keep attic temperatures down.Maintain and Clean ShinglesRegularly removing debris and replacing damaged shingles can help ensure your roofing system is operating correctly. If you don't take care of your roof, its integrity could be compromised. It's best to leave this work to the professionals, so consider scheduling regular maintenance.Have the Roof InspectedHave your roof inspected at least twice a year for damage. Have a professional perform these inspections, as they know what to look for and can do so safely. Damage can often be seen inside your home before it shows up on your roof, so be sure the inspection looks both inside and outside for potential issues.Choose a Cool RoofInstalling a highly reflective roof (often known as a "cool roof") can help prevent early damage from the sun and may even help reduce cooling costs.1 How hot does a roof get in the summer when it's designed with "cooler" materials? A highly reflective roof can keep the surface 50°F cooler compared to traditional roofs, notes the US Department of Energy.2Benefits of Cool RoofsTwo factors affect the coolness of a roof: thermal emittance and solar reflectance. Thermal emittance is a roof's ability to shed heat by giving off thermal infrared radiation. Solar reflectance is its ability to reflect or bounce sunlight off the roof before heat is created.In general, light-colored roofs stay cooler than darker ones. However, new advances have made it possible to get cool roofs in a variety of architecturally pleasing colors. The benefits of a cool roof may include:Lowering cooling costs1Reducing the load on air conditionersEligibility for rebates and other incentives from utilities or government programs4Decreasing roof temperature, which may help extend the life of the roofCurious to learn more? Contact a local roofing professional today to find out how you can reduce the temperature of your roof, either through increased ventilation or by installing a cool roof system.1 Energy cost savings are not guaranteed and the amount of savings may vary based on climate zone, utility rates, radiative properties of roofing products, insulation levels, HVAC equipment efficiency, and other factors.2,3: From energy.gov/energysaver/cool-roofs.4 Rebates and Incentives, and their eligibility requirements vary and availability is not guaranteed.

By Authors Dawn Killough

July 13, 2023

Rolling out cooling GAF Streetbond® coating in blue and white, Pacoima, L.A.
In Your Community

Creating Net-Positive Communities: GAF Taking Action to Drive Carbon Reduction

Companies, organizations, and firms working in the building, construction, and design space have a unique opportunity and responsibility. Collectively, we are contributing to nearly 40% of energy-related carbon emissions worldwide. While the goals, commitments, pledges, and promises around these challenges are a step in the right direction, no one entity alone will make major improvements to this daunting issue.We need to come together, demonstrate courageous change leadership, and take collective approaches to address the built environment's impacts on climate. Collectively, we have a unique opportunity to improve people's lives and make positive, measurable changes to impact:Buildings, homes, and hardscapesCommunity planningConsumer, commercial, and public sector behaviorOur Collective Challenge to Reduce our Carbon FootprintAccording to many sources, including the U.S. Green Building Council (USGBC), the built environment accounts for 39% of global energy-related carbon emissions worldwide. Operational emissions from buildings make up 28% and the remaining 11% comes from materials and construction.By definition, embodied carbon is emitted by the manufacture, transport, and installation of construction materials, and operational carbon typically results from heating, cooling, electrical use, and waste disposal of a building. Embodied carbon emissions are set during construction. This 11% of carbon attributed to the building materials and construction sector is something each company could impact individually based on manufacturing processes and material selection.The more significant 28% of carbon emissions from the built environment is produced through the daily operations of buildings. This is a dynamic that no company can influence alone. Improving the energy performance of existing and new buildings is a must, as it accounts for between 60–80% of greenhouse gas emissions from the building and construction sector. Improving energy sources for buildings, and increasing energy efficiency in the buildings' envelope and operating systems are all necessary for future carbon and economic performance.Why It Is Imperative to Reduce our Carbon Emissions TodayThere are numerous collectives that are driving awareness, understanding, and action at the governmental and organizational levels, largely inspired by the Paris Agreement enacted at the United Nations Climate Change Conference of Parties (COP21) in 2015. The Architecture 2030 Challenge was inspired by the Paris Agreement and seeks to reduce climate impacts from carbon in the built environment.Since the enactment of the Paris Agreement and Architecture 2030 Challenge, myopic approaches to addressing carbon have prevailed, including the rampant net-zero carbon goals for individual companies, firms, and building projects. Though these efforts are admirable, many lack real roadmaps to achieve these goals. In light of this, the US Security and Exchange Commission has issued requirements for companies, firms, and others to divulge plans to meet these lofty goals and ultimately report to the government on progress in reaching targets. These individual actions will only take us so far.Additionally, the regulatory environment continues to evolve and drive change. If we consider the legislative activity in Europe, which frequently leads the way for the rest of the world, we can all expect carbon taxes to become the standard. There are currently 15 proposed bills that would implement a price on carbon dioxide emissions. Several states have introduced carbon pricing schemes that cover emissions within their territory, including California, Oregon, Washington, Hawaii, Pennsylvania, and Massachusetts. Currently, these schemes primarily rely on cap and trade programs within the power sector. It is not a matter of if but when carbon taxes will become a reality in the US.Theory of ChangeClimate issues are immediate and immense. Our industry is so interdependent that we can't have one sector delivering amazing results while another is idle. Making changes and improvements requires an effort bigger than any one organization could manage. Working together, we can share resources and ideas in new ways. We can create advantages and efficiencies in shared R&D, supply chain, manufacturing, transportation, design, installation, and more.Collaboration will bring measurable near-term positive change that would enable buildings and homes to become net-positive beacons for their surrounding communities. We can create a network where each building/home has a positive multiplier effect. The network is then compounded by linking to other elements that contribute to a community's overall carbon footprint.Proof of Concept: GAF Cool Community ProjectAn estimated 85% of Americans, around 280 million people, live in metropolitan areas. As the climate continues to change, many urban areas are experiencing extreme heat or a "heat island effect." Not only is excess heat uncomfortable, but heat islands are public health and economic concerns, especially for vulnerable communities that are often most impacted.Pacoima, a neighborhood in Los Angeles, was selected by a consortium of partners as a key community to develop a first-of-its-kind community-wide research initiative to understand the impacts various cooling solutions have on urban heat and livability. Pacoima is a lower income community in one of the hottest areas in the greater Los Angeles area. The neighborhood represents other communities that are disproportionately impacted by climate change and often underinvested in.Implementation:Phase 1: This included the application of GAF StreetBond® DuraShield cool, solar-reflective pavement coatings on all ground-level hard surfaces, including neighborhood streets, crosswalks, basketball courts, parking lots, and playgrounds. The project also includes a robust community engagement process to support local involvement in the project, measure qualitative and quantitative impact on how cooling improves living conditions, and ensure the success of the project.Phase 2: After 12 months of monitoring and research, GAF and partners will evaluate the impact of the cool pavements with the intent to scale the plan to include reflective roofing and solar solutions.This ongoing project will allow us to evaluate for proof of concept and assess a variety of solutions as well as how different interventions can work together effectively (i.e., increasing tree canopies, greenspacing, cool pavements, cool roofs, etc.). Through community-wide approaches such as this, it's possible that we could get ahead of the legislation and make significant innovative contributions to communities locally, nationally, and globally.GAF Is Taking Action to Create Community-wide Climate SolutionsWith collaboration from leaders across the building space and adjacent sectors, we believe it is possible to drive a priority shift from net neutral to net positive. Addressing both embodied and operational carbon can help build real-world, net-positive communities.We invite all who are able and interested in working together in the following ways:Join a consortium of individuals, organizations, and companies to identify and develop opportunities and solutions for collective action in the built environment. The group will answer questions about how to improve the carbon impacts of the existing and future built environment through scalable, practical, and nimble approaches. Solutions could range from unique design concepts to materials, applications, testing, and measurement so we can operationalize solutions across the built environment.Help to scale the Cool Community project that was started in Pacoima. This can be done by joining in with a collaborative and collective approach to climate adaptation for Phase 2 in Pacoima and other cities around the country where similar work is beginning.Collaborate in designing and building scientific approaches to determine effective carbon avoidance—or reduction—efforts that are scalable to create net-positive carbon communities. Explore efforts to use climate adaptation and community cooling approaches (i.e., design solutions, roofing and pavement solutions, improved building envelope technologies, green spacing, tree coverage, and shading opportunities) to increase albedo of hard surfaces. Improve energy efficiency to existing buildings and homes and ultimately reduce carbon at the community level.To learn more and to engage in any of these efforts, please reach out to us at sustainability@gaf.com.

By Authors Jennifer Keegan

May 31, 2023

Don't miss another GAF RoofViews post!

Subscribe now