Cool Roofs in Northern Climates Provide More Bang for the Buck Than We Thought

Electricity demand in Washington, D.C., plotted against daily high temperature. Source: Weather Underground, PJM Interconnection (PJME).

(Figure 1) Electricity demand in Washington, D.C., plotted against daily high temperature. Source: Weather Underground, PJM Interconnection (PJME).

The energy savings from cool, reflective, roofs have long made them the go-to roof choice in warmer and temperate climates here in the United States. Both ASHRAE and the International Energy Conservation Code have included roof surface reflectivity requirements for a number of years. About half of all new flat roofs installed in the country are highly reflective and in some product categories white options outsell dark ones by a substantial margin. It is hard to argue with the notion that, where it is warm, the roofs should be white. While the building-level impacts of cool roofs in cool climates has been covered in the past, very little has been written about the broader economic benefits of cooler buildings and cities. When we include the economic impacts of factors like improved health, air quality, and energy savings, the case for cool roofs in cool climates looks even better.

The Benefits of Cool Roofs Go Way Beyond the Building

The building-level impacts of cool roofs are a central part of the discussion about whether they should be used in cold climates. However, it is also important to recognize the substantial co-benefits that come from installing cool roofs in terms of healthier and more comfortable people, improved productivity, better air quality, and increased economic prosperity. While the economic benefits of cool roofs are substantial, they may not always be fully included in a building owner’s roof buying decision.

How much cooler could our cities become if we added more reflective roofs? In a comprehensive review on this topic, Santamouris 2012 found that when a global increase of the city’s albedo is considered, the expected mean decrease of the average ambient temperature is close to 0.5°F (0.3°C) per 0.1 increase in reflectivity, while the corresponding average decrease of the peak ambient temperature is close to 1.6°F (0.9°C). The cooling impact of reflective roofs in certain neighborhoods could be significantly better, though. A study of Chicago by Notre Dame University found that installing reflective roofs cooled city surfaces by around 3.5 to 5.5°F (2-3°C), but surfaces in the downtown core cooled by 12.5 to 14.5°F (7-8°C).

Cool Cities Are Energy Savers

We have started to better understand and quantify the impact in cities that are able to get a degree or two of cooling. The most obvious benefit is that cooler cities demand less energy on hot days. The graph in Figure 1 plots electricity demand in

Lowering the temperature of cities can bring a multitude of benefits. Source: Global Cool Cities Alliance.

(Figure 2) Lowering the temperature of cities can bring a multitude of benefits. Source: Global Cool Cities Alliance.

Washington, D.C., against the maximum temperature every day for 5 years (2010–2015). The graph’s shape looks very similar to plots from other cities with high penetrations of air conditioning units. Demand for electricity climbs rapidly above about 80°F. When the maximum temperature is 90°F, the city requires 21 percent more electricity, on average, than on 80°F days. At 95°F, demand has spiked by nearly 40 percent over the 80°F baseline. Charges for peak electricity demand are a major expense for commercial and industrial building operators and, in seventeen states, for homeowners as well. Further, peaking demand is often met by less efficient, more expensive, and dirtier power plants that worsen air quality. At worst, peak demand can cause productivity-killing service interruptions or brownouts.

Cooler Cities Are Healthier Places

Heat is a potent but silent killer. On average, heat kills more people than any other natural disaster, and heat-related deaths tend to be underreported. In 2015, Scientific American reported that 9 out of the 10 deadliest heat events in history have occurred since 2000 and have led to nearly 130,000 deaths. Cities on dangerously hot days experience 7 percent to 14 percent spikes in mortality from all causes.

Heat stress and stroke are only the tip of the pyramid of heat health impacts. Heat puts significant additional stress on people already suffering from diseases of the heart, lungs, kidneys, and/or diabetes. A recent study finds that every 1.5°F increase in temperatures will kill 5.4 more people per 100,000 people every year.

Installing cool roofs or vegetation can lead to a meaningful reduction in heat deaths by making the daytime weather conditions more tolerable. There are a number of studies estimating the impact of increasing urban reflectivity and vegetative cover on weather conditions. Kalkstein 2012 and Vanos 2013 looked at past heat waves in 4 U.S. cities and modeled the impact of increasing reflectivity by 0.1 (the estimated equivalent of switching about 25 percent of roofs from dark to light colors) and vegetative cover by 10 percent. Though the sample sizes are too small to draw sweeping conclusions, the studies found that cities making these modest changes could shift weather into less dangerous conditions and reduce mortality by 6 percent to 7 percent.

Cooler Cities Are Engines of Economic Growth

The health, air quality, and energy benefits of modest increases in urban roof reflectivity could generate billions of dollars of

An infrared scan of Sacramento, Calif., shows the range of surface temperatures in the area. Source: Lawrence Berkeley National Laboratories.

(Figure 3) An infrared scan of Sacramento, Calif., shows the range of surface temperatures in the area. Source: Lawrence Berkeley National Laboratories.

economic prosperity for our cities. A study of 1,700 cities published in the Journal Nature Climate Change found that changing only 20 percent of a city’s roofs and half of its pavement to cool options could save up to 12 times what they cost to install and maintain, and reduce air temperatures by about 1.5°F (0.8°C). For the average city, such an outcome would generate over a $1 billion in net economic benefits. Best of all, adding cool roofs to between 20 and 30 percent of urban buildings is a very realistic target if existing urban heat island mitigation policy best practices are adopted.

Cool Roof Performance in Cold Climates: In Brief

As positive as cool roofs are for cities in cool climates, they first have to be a high-performing choice for the building itself. What do we know about net energy savings in cool climates with higher heating load? This question was the subject of “There is Evidence Cool Roofs Provide Benefits to Buildings in Climate Zones 4-8” in the November/December 2016 issue of Roofing that summarized the newest science and field studies that show that reflective roofs provide net energy benefits and favorable heat flux impacts on roofs in cold climates. In short, the newest research from Columbia, Princeton and others demonstrates that the size of the “winter heating penalty” is significantly less than many had thought and shows net reductions in annual energy use when cool roofs are used, even with roof insulation levels as high as R48.

Real Cool Roofs in Cold Climates: The Target Survey

It is not just the science that supports the use of reflective roofs in cold climates. The strong and steady growth of cool roofing in northern markets over the last decade or two is also a good indication that reflective roofs are a high-performance option in those areas. For almost 20 years, Target Corporation has installed reflective PVC membranes on nearly all of its stores in the

Studies estimate that modest increases in urban roof reflectivity could generate billions of dollars of economic prosperity for cities. Pictured here is the roof on the Cricket Club in Toronto. Photo: Steve Pataki

Studies estimate that modest increases in urban roof reflectivity could generate billions of dollars of economic prosperity for cities. Pictured here is the roof on the Cricket Club in Toronto. Photo: Steve Pataki

United States and Canada. The membranes are usually installed over a steel deck with no vapor retarder. Target and manufacturer Sika Corporation undertook a field study of 26 roofs on randomly chosen stores located in ASHRAE Climate Zones 4-6 including Connecticut, Illinois, Massachusetts, Michigan, Minnesota, New York, Washington, and Wisconsin. The roofs were 10-14 years old at the time of the survey. None of the 51 total roof sample cuts were made across these roofs showed signs of condensation damage. A more detailed accounting of the study by representatives of Target Corporation and Sika Sarnafil published in Building Enclosure includes this important paragraph from authors Michael Fenner, Michael DiPietro and Stanley Graveline:

“Specific operational and other costs are confidential information and cannot be disclosed. However, it can be stated unequivocally that although the magnitude varies, Target has experienced net energy savings from the use of cool roofs in all but the most extreme climates. Although the savings in northern states are clearly less than those achieved in southern locations, experience over approximately two decades has validated the ongoing use of cool roofs across the entire real estate portfolio. Even in climates with lengthy heating seasons, overall cooling costs exceed heating costs in Target’s facilities.”

It is increasingly clear that installing cool roofs is the definition of “doing well by doing good.” Even in cold areas, a properly built roof system with a reflective surface is a high-performance option that delivers value for building owners while making hugely positive contributions to the neighborhoods and cities they occupy.

Virginia Tech Study Measures the Impact of Membranes on the Surrounding Environment

Equipment tripods are set up to hold air temperature and EMT temperature sensors.

Equipment tripods are set up to hold air temperature and EMT temperature sensors.

For much of the past decade, the debate over when and where to install reflective roofing has been guided by two basic assumptions: first, since white roofs reflect heat and reduce air conditioning costs, they should be used in hot climates. Second, since black membranes absorb heat, they should be used in cool-to-colder climates to reduce heating costs. This reasoning has been broadly accepted and even adopted in one of the most influential industry standards, ASHRAE 90.1, which requires reflective roofing on commercial projects in the warm-weather portions of the United States, Climate Zones 1–3.

But as reflective membranes have become more widely used, there has been a growing awareness that the choice of roof color is not simply a matter of black or white. Questions continue to be debated not only about the performance and durability of the different types of membranes, but on the impact of other key components of the roof system, including insulation and proper ventilation. The issue of possible condensation in cooler or even cold climates is garnering more attention. Given these emerging concerns, the roofing community is beginning to ask for more detailed, science-based information about the impact of reflective roofing.

One recent area of inquiry is centering on the impact of “the thermal effects of roof color on the neighboring built environment.” In other words, when heat is reflected off of a roofing surface, how does it affect the equipment and any other structures on that roof, and how might the reflected heat be impacting the walls and windows of neighboring buildings? Put another way, where does the reflected heat go?

THE STUDY

To help answer those questions, the Center for High Performance Environments at Virginia Tech, supported by the RCI Foundation and with building materials donated by Carlisle Construction Materials, designed and implemented a study to compare temperatures on the surface and in the air above black EPDM and white TPO membranes. In addition, the study compared temperatures on opaque and glazed wall surfaces adjacent to the black EPDM and white TPO, and at electrical metallic tubing (EMT) above them.

Specifically, the Virginia Tech study was designed to answer the following questions:

  • What is the effect of roof membrane reflectivity on air temperatures at various heights above the roof surface?
  • What is the effect of roof membrane reflectivity on temperatures of EMT at various heights above the roof surface?
  • What is the effect of roof membrane reflectivity on temperatures of opaque wall surfaces adjacent and perpendicular to them?
  • What is the effect of roof membrane reflectivity on temperatures of glazed wall surfaces adjacent and perpendicular to the roof surface?

To initiate the study, the Virginia Tech team needed to find an existing roof structure with the appropriate neighboring surfaces. They found a perfect location for the research right in their own backyard. The roof of the Virginia-Maryland College of Veterinary Medicine at Virginia Tech was selected as the site of the experiment because it had both opaque and glazed wall areas adjacent to a low-slope roof. In addition, it featured safe roof access.

In order to carry out the study, 1.5 mm of reinforced white TPO and 1.5 mm of non-reinforced black EPDM from the same manufacturer were positioned on the roof site. A 12-by-6-meter overlay of each membrane was installed adjacent to the opaque wall and a 6-by-6-meter overlay of each was installed next to the glazed wall. At each “location of interest”—on the EPDM, on the TPO, and next to the opaque and glazed walls—the researchers installed temperature sensors. These sensors were placed at four heights (8, 14, 23, and 86 centimeters), and additional sensors were embedded on the roof surface itself in the TPO and EPDM. Using these sensors, temperatures were recorded on bright, sunny days with little or no wind. The researchers controlled for as many variables as possible, taking temperature readings from the sensors on and above the EPDM and TPO on the same days, at the same time, and under the same atmospheric conditions.

The roof of the Virginia-Maryland College of Veterinary Medicine at Virginia Tech is the site of the experiment because it has opaque and glazed wall areas adjacent to a low-slope roof.

The roof of the Virginia-Maryland College of Veterinary Medicine at Virginia Tech is the site of the experiment because it has opaque and glazed wall areas adjacent to a low-slope roof.

THE RESULTS

The output from the sensors showed that at the surface of the roof, the black membrane was significantly hotter than the white membrane, and remained hotter at the measuring points of 8 cm and 14 cm (just over 3 inches and 5.5 inches, respectively). However, the air temperature differences at the sensors 23 centimeters (about 9 inches) and 86 centimeters (just under three feet) above the surface of the roof were not statistically significant. In other words, at the site the air temperature just above the white roof was cooler, but beginning at about 9 inches above the roof surface, there was no difference in the temperature above the white and black membranes.

On the precast concrete panel adjacent to the TPO and EPDM, temperatures were warmer next to the TPO than adjacent to the EPDM, leading the study authors to hypothesize that the TPO reflected more heat energy onto the wall than did the EPDM. Exterior glazing surface temperatures were found to be approximately 2 degrees Celsius hotter adjacent to the TPO overlay as compared to the EPDM overlay.

Elizabeth Grant led the team that designed and implemented the study. She says her findings show that you need to take the entire environment into account when designing a roof system. “You need to think about what’s happening on top of the roof,” she says. “Is it adjacent to a wall? Is it adjacent to windows? Is it going to reflect heat into those spaces?”

Samir Ibrahim, director of design services at Carlisle SynTec, believes the study results will help frame additional research. “These findings are an important reminder that the full impact of reflective roofing on a building and on surrounding buildings is not fully understood,” he says. “Additional research and joint studies, covering different climatic conditions, are certainly warranted to broaden the knowledge and understanding of the true impact on the built-environment.”

Kemper System Will Showcase Liquid-Applied Protective Solutions at IRE

Kemper System America Inc. will showcase a range of cold liquid-applied protective solutions for the building envelope at the International Roofing Expo (IRE) in Las Vegas, March 1-3, and demonstrate product application at booth 217.

Kemper System protects surfaces across the globe. Solutions to be featured at IRE include:

  • Two fully reinforced membrane systems that can transform roof decks into reflective cool roofs, or provide monolithic protection for green roofs, blue roofs, and a range of other projects.
  • Two new coatings systems for protecting surfaces prone to heavy wear such as parking garages, balconies and walkways.

Waterproofing Membrane Systems

The two reinforced waterproofing membrane systems are cold liquid-applied and ideal for cool roof applications:

  • Kemperol AC Speed FR system is a Polymethyl Methacrylate (PMMA)
  • Kemperol Reflect 2K FR is a low-VOC system

Both are fire rated for Class A assemblies and exceed LEED solar reflective requirements with SRI ratings of 108 and 110, respectively.

Durable Wear Coatings

For protecting parking garages, pedestrian decks, and loading docks, the COLEAN Parking System can withstand deterioration caused by natural elements and vehicular traffic. In addition, the COLEAN Balcony System, which is designed to expand and contract with normal structural movements, protects balconies, terraces, walkways, patios, sun decks, and machine rooms from freeze/thaw damage and chemical exposure.

Kemper System America also offers a way to prolong the life of existing roofs with elastomer-based coating systems, one of four technologies added through the acquisition of STS Coatings Inc. in December.

“Our building envelope solutions go beyond roof waterproofing to make the building specifier’s job easier. These solutions create opportunities for contractors and value for building owners,” says Richard Doornink, president and managing director of Kemper System America Inc.

For over 60 years, Kemper System has led in cold-liquid applied, reinforced roofing and waterproofing, having invented the technology and holding the first patents. Today the company offers a range of building envelope solutions to protect against weather, preserve the integrity of surfaces, and enhance the comfort and value of public buildings and commercial real estate.

Visit IRE booth 217 to learn more, or contact Kemper System at inquiry@kempersystem.net, or call 8(800)541-5455.

RCMA and Members of Congress Address Issues of the Roof Coatings Industry

Members of the Roof Coatings Manufacturers Association (RCMA) met with its members of Congress on Capitol Hill as part of the Association’s Summer Meeting and Legislative Day.

More than 30 RCMA members participated in the Legislative Day, which entailed paying visits to members of Congress and key congressional staffers from their states and districts. RCMA scheduled meetings with more than 80 congressional offices, offering opportunities for manufacturers and suppliers to the industry to communicate to lawmakers the issues of importance to the roof coatings industry.

“The meetings on Capitol Hill gave RCMA members the chance to highlight the issues that are important to our industry,” says John Ferraro, RCMA’s executive director. “It was clear many of the senators, representatives and legislative staffers we met with were receptive to these industry issues, and therefore RCMA will be continuing the dialogue with these congressional offices.”

In particular, RMCA members discussed three main issues of interest to the roof coatings industry: opposing the Environmental Protection Agency (EPA) from further lowering the National Ozone Standard, supporting the Clean Air, Strong Economies (CASE) Act, and advocating for a federal tax credit for reflective roof coatings.

The RCMA opposes the EPA’s proposal to lower the National Ozone Standard. Reductions to the standard have resulted in implementation of hundreds of regulations that created a tremendous regulatory burden. Consequently, the rule forced industries to spend billions of dollars to reformulate their products to achieve new volatile organic compound (VOC) content limits. Over the last few decades, 90 percent of VOC content has been eliminated from roof coatings, and further reduction of VOCs can have a wide variety of unintended consequences.

The RCMA supports the CASE Act (Senate Bill 751 and House Bill 1388). The bill would prohibit the U.S. EPA from lowering the National Ambient Air Quality Standard (NAAQS) until at least 85 percent of counties that are in nonattainment areas have attained the standard.

To incentivize building owners to make the investment to save energy and reduce roofing waste, the RCMA supports the creation of a federal tax credit for reflective roof coatings applied to low slope roof surfaces on multi-family residential, commercial and industrial buildings.

RCMA Offers an Educational Presentation on Reflective Roof Coatings

The Roof Coatings Manufacturers Association (RCMA) has launched its Speakers Bureau program to offer an educational presentation on reflective roof coatings. RCMA’s Speakers Bureau consists of several RCMA members with expertise on the topic who have volunteered to deliver presentations throughout the country.

This presentation, titled “Reflective Roof Coatings: Cool Stories,” is approximately one hour in length, and discusses the key benefits and the environmental importance of reflective roof coatings used on low-slope roof systems. The science behind reflective roof coatings is presented in an easy-to-understand format and real-world case studies are presented to illustrate the information presented. The presentation content is intended to enable attendees to:

  • Understand the benefits that reflective roof coatings impart on low-slope roof systems.
  • Recognize why reflective roofs are environmentally important and comprehend the science behind how reflective roofs save energy.
  • Determine best practices for preparing a roof membrane and application methods for reflective roof coatings on low-slope roof systems.
  • Identify payback, energy savings, and other non-quantifiable benefits by evaluating several real-world roof-reflectivity case studies.

RCMA is an approved continuing education provider with the American Institute of Architects (AIA) and RCI Inc. By attending the course, attendees qualify to earn 1 AIA General Learning Unit Hour (1 LU Hour) as part of AIA’s Continuing Education System or 1 RCI Continuing Education Hour (CEH).

Groups interested in offering this presentation at an upcoming meeting or event should contact RCMA Staff Associate Cecily Alfonsi to participate.

RCMA Enhances Reflective Roof Rebates Database

The Roof Coatings Manufacturers Association (RCMA) launched an enhanced Reflective Roof Rebates Database with increased functionality for searching available reflective roof incentives across the country. Created exclusively for use by RCMA members, the customized search tool can be used to find the most up-to-date listings of local, state, federal, and utility financial incentives available for installing reflective roofs.

The enhanced search tool now allows users to filter results to show comprehensive energy rebates, reflective roof rebates, or all available rebates. Available only to members of the RCMA, the database searches by state or ZIP code to find available financial incentives and has proven an essential tool for members’ sales teams to use when speaking with prospective customers.

“Since its launch, the RCMA Reflective Roof Rebates Database has been one of our most popular member benefits,” says John Ferraro, RCMA executive director. “Independently tracking such a wide array of financial incentives has proven a challenge for our members for years, and they now have come to rely on this user-friendly tool to take the work out of discovering relevant rebates for the installation of reflective roofs all across the United States.”

Additional improvements to the database include the addition of more detailed information on each of the available incentive programs including eligibility, links to supporting documents, key program contacts, and online applications to apply for rebates. A newly-added print view allows RCMA Members to more easily review the available information in a ready-to-share format.

The RCMA Solar Reflective Coatings Council (SRCC), representing the producers of acrylic and elastomeric (non-bituminous) coatings and suppliers to the industry, initiated the creation of the Reflective Roof Rebates Database in 2013 and it has been met with tremendously positive feedback from the industry since its launch.

For more information on how to join the RCMA and acquire access to the database, email RCMA Staff Associate Laura Dwulet.