Cool Roofing for Cool Climates  

Here’s an alarming fact: Planet Earth has warmed 1.26 degrees Fahrenheit in the past century, which is approximately 10 times faster than typical warming rates. But what’s worse is the localized urban heat island (UHI) effect has caused the annual average temperature in a city of a million people to increase between 1.8 and 5.4 degrees Fahrenheit, according to the U.S. Environmental Protection Agency, and this number can jump to as high as 22 degrees Fahrenheit warmer in the evening hours.

Photo courtesy of GAF

This relective membrane crowning the U.S. Bank building in Boise, Idaho, demonstrates the effectiveness of cool roofs in all climate zones.

Defined as a metropolitan area that is significantly warmer than surrounding rural areas due to a concentration of buildings and human activities, the urban heat island effect has taken hold in today’s urban environments, currently populated by more than half of the world’s inhabitants.

With an increase in heat waves, periods of abnormally hot weather, and increased health issues—particularly amongst the elderly and those with conditions such as asthma—the UHI threat is real.

Of particular concern is the application of dark-colored roofs, especially in these urban environments, as Lawrence Berkeley National Laboratory researchers report in a 2013 paper titled “Economic comparison of white, green, and black flat roofs in the United States” in the Energy and Buildings journal, “The sunlight that is absorbed heats the roof, which increases cooling costs in air-conditioned buildings, increases discomfort in unconditioned buildings, increases mortality during heat waves, and pollutes local and regional air.”¹

Case in point, a July 1995 heat wave took the lives of 739 Chicagoans, with virtually all those deaths occurring on the top floors of black-roofed buildings without air-conditioning. As reported by Chicago magazine, in 2015, in looking back at that 1995 heat wave, “by the afternoon, temperatures hit 104 at O’Hare and 106 at Midway. It felt like 125, according to the heat index, which factors in humidity. In what’s known as the heat island effect, brick buildings, asphalt parking lots, and tar roofs trapped the warmth and then radiated it outward.”²

The Cool Roof Solution

Fortunately, there are ways to successfully mitigate escalating rooftop heat, directly impacting UHI levels. Selecting light-colored membranes in place of dark roofing not only decreases the UHI impact, but it also increases the reflectivity of sunlight, thus reducing heat within the building and cutting down on energy demand.

“City roofs are traditionally black…but from a climate and urban heat island standpoint, it makes a lot of sense to install bright, white roofs,” states Stuart Gaffin, research scientist, Center for Climate Systems Research, Columbia University, New York, in a blog post titled “New York Roofs: Brighter, Whiter, Cleaner.”³

Conversely, “TPO/PVC roofs are basically reflective rooftops that reflect the sun’s radiations back into the atmosphere and do not allow it to be absorbed by the rooftop, thus inhibiting transfer of energy/heat in the buildings. This keeps the buildings cooler in comparison to conventional roofs,” explains Ashish Sharma, Ph.D., research assistant professor, Department of Civil & Environmental Engineering & Earth Sciences, Notre Dame University, Notre Dame, Indiana.

In fact, New York’s White Roof Project calculates that white roofs can save building owners up to 40 percent on their electricity bills. Furthermore, if all urban rooftops worldwide would be converted to white, the planet would save 24 billion metric tons of carbon dioxide. To understand how significant this could be, this value is the equivalent of total world emissions of the greenhouse gas in 2010.

As opposed to darker membranes—for example, ethylene propylene diene monomer (EPDM), which absorbs more than 90 percent of the sun’s rays, thereby heating the rooftop to high temperatures and subsequently the building—light-colored membranes only absorb 20 to 25 percent of the sun’s energy.

Photo courtesy of Shutterstock

Many cultures, such as Santorini, Greece, understood the importance of building reflectivity as a way of reducing internal temperatures long before the advent of air-conditioning.

In fact, the LBNL reports that white or light-colored membranes can reduce the roof’s surface by more than 40 degrees Fahrenheit, as compared to a dark-colored membrane. Originally documented by an LBNL study of a retail store in Austin, Texas, by switching from a black membrane to a white one, the facility’s average summertime rooftop surface temperature decreased from 168 to 126 degrees Fahrenheit.⁴

Converting this into dollars and cents, the study recorded a peak-hour cooling energy savings of 14 percent and overall annual energy savings of 7.2 cents per square foot, which, adjusted for inflation in 2017, would be approximately 10 cents per square foot.

In addition to these energy savings, cool roofs are longer lasting and require less maintenance as compared to black roofs which must withstand much higher temperatures. For example, EPDM roof membranes can shrink over time due to the effects of high heat. This shrinkage can lead to failure of the adhesive seams, as they generally don’t perform well after long-term exposure to heat.

According to the U.S. Department of Energy’s Energy Efficiency & Renewable Energy Building Technology Program’s Guideliens for Selecting Cool Roofs, in cases where heat-related degradation is the main reason for roof failure, it is plausible that a cool roof could be more durable and outlast a similar dark roof.⁵

Another LBNL study conducted for the Federal Energy Management Program concluded that by increasing the roof albedo to moderate and high levels in 2003, this would yield $16 million and $32 million in energy cost savings, respectively.⁶

“Clearly, FEMP should encourage use of cool roofs in new construction and during regularly scheduled reroofing to keep incremental costs down,” states the report. Factoring in more recent data, LBNL estimates that utilizing cool roofing on 80 percent of commercial buildings in the United States would result in 10,400 gigawatt-hours of cooling energy savings and approximately $735 million in annual overall energy savings. In addition, the product lifetime energy savings has a present value of $11 billion.

Photo courtesy of GAF

If cool roofing were to be installed in 80 percent of U.S. commercial buildings, 10,400 gigawatt-hours of cooling energy savings could be saved each year, according to the Lawrence Berkeley National Laboratory.

LBNL researchers also predict that installing cool pavements and trees across 30 percent of the Los Angeles basin surface could decrease local temperatures by as much as 5 degrees Fahrenheit. With a lowered ambient temperature, the area’s annual building cooling savings could be as high as 50 percent by simply installing cool roofs.

In yet another noted study, this one by the Oak Ridge National Laboratory, researchers estimated how much insulation would have to be added to dark roofs in order to achieve the same energy savings of cool roofs. They concluded that an average R-9 value in insulation would be required to enable dark-colored membranes to deliver the same cooling cost savings as reflective roofs.

Cool Roofing in Northern Climates

Although cool roofing’s ability to mitigate the UHI is well established in warmer climates, can they be effective in northern regions?

“Yes, they can,” affirms Brett Polhill, territory sales and service manager, NIR Roof Care, Rockford, Illinois. “While the cooling savings would not be as high as in southern climates, the cooling energy savings outweigh the heating energy savings.”

Image courtesy of GAF

Cool roofs are not relegated to only southern climates. As pictured here, this U.S. Bank building in Boise, Idaho, is actively saving HVAC costs and helping to mitigate the urban heat island effect.

“While this impact will be more significant in warmer climates, there is an impact in northern climates,” agrees Dr. Trevor Nace, who holds a PhD. From Duke University in geology and climate, and is a contributing author to Forbes covering geology, earth science, and natural disasters.

That said, many building owners have the impression that dark roofing can help heat buildings in the winter.

Addressing this issue, Thomas J. Taylor, executive director building and roofing science, GAF Materials, Parsippany, New Jersey, points out a number of things. Firstly, during the winter, the angle of the sun is relatively low, so heat absorption isn’t very significant. Furthermore, the winter days are more frequently cloudy and snowy, further inhibiting the effectiveness of heat absorption on the rooftop.

Another important point is the fact that in all parts of North America, there are much fewer hours of daylight during the winter months. In fact, in some areas, there is a greater than a 6-hour difference between peak-summer and peak-winter sunlight. The upshot is there is far less sunlight available to contribute to a building’s potential warming.

Emphasizing this point, Stanley P. Graveline, technical committee member, Vinyl Roofing Division of the Chemical Fabrics and Film Association, explains that in northern states, winter solar irradiance is typically 20 to 35 percent of the summer irradiance. This means that a roof surface receives three to five times more sun during the summer than during the winter months.

To the extent that dark roofs help to reduce heating costs in the winter, the cooling energy costs during the summer for a TPO/PVC roof will offset the loss in heating savings of a dark membrane roof, explains Polhill.

Image courtesy of GAF

By rejecting heat as opposed to absorbing it, cool roofs keep buildings cooler in the summer, thereby reducing air-conditioning costs.

Addressing this issue, University of Wisconsin-Madison’s College of Engineering’s HVAC&R Center studied simulated “big box” black- and white-roofed retail buildings in Denver and Minneapolis.

“Their analysis demonstrates that even in such northern cities, cooling energy savings can be sufficient to compensate for any heating energy penalties that may be incurred through using cool roof surfaces,” concludes Graveline in a National Roofing Contractors Association (NRCA) Professional Roofing article titled “Still cool after all these years.”⁷

In a nutshell, the energy required to air-condition a building in the summer is often quite a bit more than the energy required to heat it in the winter, effectively correcting the misperception that if heating degree days outnumber cooling degree days, dark roofing should be specified. In fact, on average, it’s four times more expensive to cool in the summer with electricity vs. heating a building in the winter with gas. This means that the potential for summer energy cost savings are much greater with a highly reflective white roof than the winter savings offered by a heat-absorbing black roof.

Bringing up an important point, David Defilippo, AIA, architect, Tsoi Kobus Design, Boston, says, “You don’t heat a building by warming the roof—at least not yet.”

Another issue, as noted by the White Roof Project, is the fact that the laws of physics dictate that hot air will always rise, so any heat that is transferred to the interior of a building structure from the outside will remain at the top of the structure, thereby minimizing heat savings.

On Target

On the topic of cool roofing in northern climates, Target Corporation, which almost exclusively utilizes white PVC membranes on its stores, studied the energy savings delivered by its cool roofs.⁸

Based on the results of Target’s research, Graveline, one of the study’s authors, states in the Roofing Contractor article, “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.”

He added that for Target’s few dark roofs, the company has not seen any measurable reduction of energy consumption during heating seasons that can be attributed to heat gain via the roof in northern climates.

In terms of the reduction of cooling expenses during the summer months, Taylor emphasizes that the days in northern cities are longer as opposed to southern climates, and the sun is high in the sky. So if the roof is not reflective, this can increase the load on air-conditioning systems.

That said, it is true that rooftop temperature reductions and subsequent cooling energy savings are more pronounced in southern climates. This is clearly highlighted in most roofing energy modeling programs, whereas the economic case for northern climate light-colored roofing is often understated because the calculation tool fails to take into consideration utility demand charges.

With typical utility pricing structures charging commercial end users based upon both overall monthly electricity use and the maximum demand level during that month, this forces building owners to look at these loads much more critically.

“Utility companies have to worry about two things when supplying a region: how much power they have to supply each month or quarter, and how to manage maximum demands that can occur when things like air-conditioning loads are at their highest,” Taylor explains. “They focus on the high demands that occur in a short period of time and will penalize a building owner for them.”

To differentiate between peak charges and demand charges, the former is when a utility charges a higher dollar per kilowatt hour rate (kWHr) structure at peak times, for example, between 1 and 6 p.m. during the summer months. This peak charge will apply equally to all end users.

In addition, demand charges are based on the highest 15 minutes of electric use by an end user. This charge is calculated as dollars per kilowatt of demand—i.e., the fastest speed that their electric meter runs in one month, even if for only 15 minutes. In an extreme case, the user might only turn on their AC once for 15 minutes in July, but they will get hit with a very large demand charge because the unit required a huge amount of power for that time.

As an example case provided by the U.S. Department of Energy, if one end user utilizes a 5 kW load spread out over 500 hours at rate of $0.15, a demand charge of $28 will only be applied to the 5 kW. This will result in a $515 utility bill. On the other hand, a 50 kW condensed into 50 hours uses the same amount of electricity but significantly condenses the load profile, forcing the end user to pay a much higher rate for drawing such a large load at peak times. The result, in this case, is a $1,775 bill, more than three times as expensive as the first scenario.

Image courtesy of the U.S. Department of Energy

A 5 kW load spread out over 500 hours result in a $515 utility bill, whereas a 50 kW condensed into 50 hours uses the same amount of electricity but produces a $1,775 bill from demand charges.

“Commercial peak rates are typically higher during midday, so it is in the electrical customer’s best interest to trim their peak demand usage and/or shift the usage to off-peak hours,” recommends Shad L. Traylor, AIA, NCARB, CDT, MBA, LEED AP BD+C, senior architect, BRPH, Melbourne, Florida.

It follows that if a light-colored roof can effectively reduce the electric demand in peak periods, this will improve the economics of a cool roof, says Gary P. Moshier, AIA, LEED AP BD+C, CPHD, partner, Moshier Studio, Pittsburgh.

Overall, as energy consumption continues to increase, more utilities will charge premium rates during peak demand times as a mechanism to motivate building owners to flatten out their load profiles.

In fact, the United Nations Intergovernmental Panel on Climate Change predicts that in most North American cities, a once-in-20-years hottest temperature event will start occurring every two years. Furthermore, that hottest temperature event will increase by 3.5 to 9 degrees Fahrenheit.

As an aside, to assist specifiers with computing demand charges, the Cool Roof Energy Savings Tool can be a helpful way to determine just how much energy savings a cool roof can deliver.⁹

Northern Cities Embrace Cool Roofing Programs

In the bigger picture, cool roofs can play a significant role in reducing peak demand across all climate zones, which is why a number of northern cities—including Chicago, New York, and Toronto—have cool roofing programs, and why California’s Title 24 energy code, ASHRAE 90.1, the U.S. Green Building Council’s LEED program, and the Green Building Initiative’s Green Globes program include cool roofs in their requirements and credits.

“Most energy-related codes and green building programs such as LEED place heavy emphasis on installation of reflective roofs,” reports Mark Kim, director of architecture, MVE + Partners, Irvine, California.

For example, NYC CoolRoofs is a part of the Big Apple’s goal to reduce carbon emissions 80 percent by 2050. To help move things along, the city offers cool roof installations at no cost or low cost to select buildings in its quest to whiten 6 million square feet of New York rooftops.

Driven by a similar greenhouse gas emissions reduction goal of 80 percent by 2050, Toronto’s Eco-Roof Incentive program offers residential, industrial, commercial, and institutional buildings the opportunity to receive $2 to $5 per square meter, up to a maximum of $50,000, for installing a reflective roof.

Meanwhile, in the Windy City, the tragic 1995 heat wave led Chicago to eventually require cool roofs on all new roofs. To help support this, Chicago’s Cool Roof Grants program gives a $0.55 rebate per square-foot on reflective roofing for a commercial facility and $0.60 for an industrial building. To qualify, both building types must have an initial reflectance of greater than or equal to 0.65 for low-slope roofing and greater than or equal to 0.25 for a medium-slope roof. Reflectivity values must either be Cool Roofs Rating Council or ENERGY STAR rated.

Backing up its confidence in the effectiveness of cool roofs, a 2012 study from Yale University titled “Remotely sensing the cooling effects of city scale efforts to reduce urban heat island” used satellite images to determine that new reflective surfaces installed in Chicago between 1995 and 2008 raised the city’s overall reflectivity by 0.016.¹⁰

More recently, a Notre Dame study, “Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model,” reported that the use of roofs with vegetation or reflective surfaces on top of Chicago’s current infrastructure could reduce the UHI effect by lowering roof temperatures between 5.4 and 7.2 degrees Fahrenheit.¹¹ In collaboration with the City of Chicago, the researchers examined the efficacy of green or cool roofs using a regional climate model to simulate various real-world urban rooftop conditions.

In light of all these programs, Andre Desjarlais, program manager, U.S. Department of Energy’s Oak Ridge National Laboratory Building Envelope research program, states in a Building Operating Management (BOM) article titled “Do Cool Roofs Fit in Cool Climates?”, “The peak demand benefits of cool roofing are the same no matter how far north you march.”¹²

Similarly, Scott Kriner, technical director, Metal Construction Association and chairman of the Cool Metal Roofing Coalition, asks why utility companies would offer incentives in cold climates if there wasn’t a benefit.

Further stating the case for cool roofing in cool climates, Hashem Akbari, staff scientist and group leader for Lawrence Berkeley National Laboratory’s Heat Island Group, Berkeley, California, states in the BOM article, “the only building that won’t benefit from a cool roof energy wise is one that’s not air-conditioned.”

In addition to incentive programs and demand charges, it’s also important to understand if and how a climate’s number of heating days and cooling days fits in. Addressing a misnomer here, Taylor explains that heating days vs. cooling days is not the right metric to look at, but rather the air-conditioning costs vs. heating costs. If heating costs are larger, then it can make sense to evaluate nonreflective roof membranes.

One question often asked about cool roofs is the extent to which they retain their reflectivity.

Most reflective materials, particularly TPOs, will retain their solar reflectance quite well as they are naturally cleaned by the rain.

Furthermore, the U.S. Environmental Protection Agency’s ENERGY STAR cool roofing program requires an initial solar reflectance of greater than or equal to 0.65 and a three-year age value of greater than or equal to 0.50. Incidentally, many of today’s reflective membranes exceed the standard.

In fact, in 2013, the Cool Roof Rating Council’s rated product directory reported that more than 90 percent of the 448 cool roof products in its directory had an aged reflectance value of 0.60 or better, and only 3 percent were below 0.55.

By cleaning the roof, those values can be restored to almost 100 percent, according to the LBNL and National Research Council Canada.

But even at the point where the membrane is not looking its cleanest, the heat energy coming from the sun makes up 50 percent of the sun’s rays, and with a wavelength longer than visible light, it goes through thin layers of dust and dirt and is still reflected by the membrane.

Debunking Condensation Myths

In convincing architects and building owners about the viability and benefits of cool roofing in northern climates, it’s important to address the myth that light-colored roofing materials are more prone to moisture build up in colder climates.

Some have questioned whether cool roofs enable more condensation to build up in the winter months, as opposed to darker membranes, and being reflective, they will not heat up sufficiently in the summer months to dry out completely. As moisture continues to accumulate, they say, eventually the roofing system’s performance is compromised.

Delving into this issue, SPRI, the association representing the single-ply roofing industry, reported on a study investigating whether cool roofs were susceptible to condensation issues. Based on WUFI modeling of 10 selected roofs with both white and black membranes, the modeling showed that any moisture would completely dry out in the summer for both the light and dark-colored roofs. Incidentally, WUFI analyzes the movement/accumulation of moisture and heat through an assembly over a period of time.

In another more well-known study, Target investigated white PVC roofs, between 10 and 14 years old on 26 stores located in the northern states of Connecticut, Illinois, Massachusetts, Michigan, Minnesota, New York, Washington, and Wisconsin. After investigating test cuts on each roof, the researchers discovered that apart from some minor leaks, there was no evidence of any moisture buildup or damage.

In yet another telling study, SPRI teamed up with Oak Ridge National Laboratory studying 10 reflective roofs located in climate zone 5. In seven of the cases, no damage was discovered on the polyisocyanurate foam insulation or facer. On three of the roofs, condensation was found on the backside of the highly reflective membrane, but minimal damage had been done to the polyiso foam insulation, and there was no rust on the roof deck.

“The conclusion from the study found that although there were signs of moisture condensation in three of the 10 roofs observed, minimal effect had occurred to the roofing assembly that would affect its integrity, insulating value, or performance,” Taylor reports.

Further commenting on the issue of condensation, the DOE’s Guidelines for Selecting Cool Roofs states, “While this issue has been observed in both cool and dark roofs in cold climates, the authors are not aware of any data that clearly demonstrates a higher occurrence in cool roofs.”

Steering the condensation conversation away from cool roofs, Phil Dregger, RRC, FRCI, P.E., Technical Roof Services, Concord, California, explains that the causes of moisture buildup in roof systems are many and varied.

“Buildings with conventional non-cool roofs can develop condensation problems, and changes other than those to roof reflectance (e.g., building use, HVAC operation) can negatively tip previously maintained balances between the wetting and drying of roof systems,” he states in a Western Roofing article titled “Cool Roofs Cause Condensation: Fact or Fiction?”¹³

Furthermore, Dr. Jim Hoff, president, TEGNOS Research, and vice president of research, Center for Environmental Innovation in Roofing, Washington, D.C., reports that moisture condensation in roofs is a relatively rare phenomenon that only occurs in unusual circumstances, such as extremely cold external temperatures, extremely high internal temperatures and humidity, unusually low amounts of above-deck roof insulation, or unusually high levels of air movement within the roofing system.

It is the case that in humid conditions, the warm air can sometimes migrate through a roof system up to the underside of the roof membrane, causing condensation to occur during the winter months in northern climates. However, this is not related to the roof material type or color and is related to roof system design.

Granted, “self-drying” dark-colored roofs will heat up and dry out in the summer should condensation occur in the winter, whereas reflective roofs tend not to dry out in the summertime, as the membrane doesn’t get hot enough.

That said, in order to ensure that condensation is not an issue with cool roofing, Taylor recommends specifying roof insulation to meet current code requirements, as this helps to move the dew point down into the insulation layers where airflow is close to zero. He also advises building teams to install two layers of nonporous insulation, such as polyiso, as opposed to mineral wool, in a staggered fashion with non-overlapping joints.

“With proper insulation, condensation is not an issue on the bottom side of the membrane,” confirms Polhill.

While this is usually sufficient, a recommended best practice is fully adhering the roof membrane as this prevents the membrane billowing during high-wind events and pulling air up into the system.

Cool TPO/PVC Roofs vs. Dark EPDM Membranes

When it comes to selecting roofing materials, TPO and PVC roofs offer a number of durability, performance, and installation advantages over EPDM roofing materials.

“Apart from this advantage related to cooling, these rooftops are aesthetically beautiful, cleaner, mold resistant, easy to install, and maintenance free,” states Notre Dame’s Ashira.

In terms of the way in which TPO/PVC thermoplastic membranes are installed, the seams are hot-air welded and fused, whereas EPDM seams are glued with temperature-sensitive adhesive or Butyl tape. The net result is the thermoplastic membrane seam strength is more than four times stronger than that of thermoset membranes.

Images courtesy of Metal Construction Association and GAF

In three easy steps, a TPO membrane is rolled out, clamped, and welded.

“The heat welding process fuses the membrane joints together, creating a continuous seam and, therefore, one membrane,” explains BRPH’s Traylor. Alternatively, “EPDM roof membranes rely on tape and adhesives at the membrane joints.”

“The welded seams are a huge advantage over the adhered seams of EPDM,” confirms Tsoi Kobus’ Defilippo.

In welding the TPO/PVC membranes, it’s easy to pull apart the test welds and see if the welding is being done correctly, whereas EPDM adhesive welds cannot be checked until the installation has cured. Furthermore, all of the flashings and details are done with hand-applied adhesive, which can be a potential workmanship issue.

Another issue with EPDM is it’s usually not reinforced, while TPO and PVC are always reinforced with a polyester fabric, making the roofs more dimensionally stable.

Yet another disadvantage with EPDM is the material tends to shrink over time, subsequently putting a lot of stress on the adhesive seams, sometimes causing the roof to fail with the seams opening up.

Photo courtesy of GAF

A less-robust seam as compared to TPO/PVC membranes, this photo depicts an EPDM seam failure.

“EPDM membranes rapidly deteriorate when different solvents and solutions leak onto the membrane, especially at the seams,” adds Polhill.

Although EPDM is available with a cool white surface, this option comes at a premium cost and is rarely utilized. Furthermore, the white EPDM has significantly less UV and ozone resistance than standard EPDM, according to Taylor.

Another point brought up by Mark Gregory, general manager, RSS Roofing Services & Solutions, Orlando, Florida, is that because EDPM can’t be ballasted, it is no longer a low-cost roof system to install, causing a noted market shift to TPO and PVC.

Looking at the Numbers

Just looking at market share, it is clear that cool roofing products continue to grow in popularity, even in cooler climates. In fact, SPRI reports that in the past 10 years, approximately 5.5 billion square feet of thermoplastic membranes were installed in ASHRAE climate zones 5 and higher, almost half of the total installed products in North America, with 2 billion square feet going into climate zones 6 and 7.

The fact is that building owners are increasingly choosing reflective roofing in all climate zones.

Image courtesy of The Freedonia Group

Highly durable, reflective TPO roofing membranes are quickly gaining market share in all climate zones.

“It’s the lowest hanging fruit. You don’t need a skilled labor force, and you don’t have to wait for a roof to be retired,” says Gaffin in reference to retrofitting New York City buildings with reflective coatings in the Columbia University blog. “So if you really talk about ways in which you brighten urban albedo, this is the fastest, cheapest way to do it.”

Summing things up in a Roofing Contractor article titled “2014 State of the Industry Report: Low-Slope Trends,” Graveline asks, “Why are we still debating the cold case of whether white roofs are effective in northern climates? There is no shortage of modeled and empirical evidence that white roof surfaces reduce building cooling energy consumption regardless of geography.”

End Notes

¹Sproul, Julian; PunWan, Man; Mandel, Benjamin H.; and Rosenfeld, Arthur H. “Economic comparison of white, green, and black flat roofs in the United States.” Energy and Buildings. March 2014. Web. 10 August 2017. www.sciencedirect.com/science/article/pii/S0378778813007652.

²Gaffin, Stuart. “New York Roofs: Brighter, Whiter, Cleaner.” State of the Planet. Earth Institute, Columbia University. 7 March 2012. Web. 10 August 2017 blogs.ei.columbia.edu/2012/03/07/new-york-roofs-brighter-whiter-cooler/.

³Thomas, Mike. “An Oral History: Heat Wave.” Chicago magazine. 29 June 2015. Web. 10 August 2017. www.chicagomag.com/Chicago-Magazine/July-2015/1995-Chicago-heat-wave/.

⁴Konopacki, S. and Akbari, H. “Energy Savings and Demand Reduction from a Reflective Roof Membrane on a Large Retail Store in Austin.” Lawrence Berkeley National Laboratory. June 2001. Web. 10 August 2017. www.vinylroofs.org/wp-content/uploads/2011/06/LBNL_study-1.pdf

⁵Guidelines for Selected Roofs. U.S. Department of Energy Building Technologies Program. July 2010. Web. 10 August 2017. www.nps.gov/tps/sustainability/greendocs/doe_coolroofguide-sm.pdf.

⁶Taha, Haider and Akbari, Hashem. “Cool Roofs as an Energy Conservation Measure for Federal Buildings.” U.S. Department of Energy Federal Energy Management Program. April 2003. Web. 10 August 2017. pubarchive.lbl.gov/islandora/object/ir%3A120601/datastream/PDF/download/citation.pdf.

⁷Graveline, Stanley. “Still cool after all these years: White reflective roofs stand up to scientific scrutiny.” Professional Roofing. October 2013. Web. 10 August 2017. www.professionalroofing.net/Articles/Still-cool-after-all-these-years--10-01-2013/2345.

⁸Fenner, Michael; DiPietro, Michael; and Graveline, Stanley. “Cool Roofs in Northern Climates.” Building Enclosure. October 2014. Web. 10 August 2017. www.buildingenclosureonline.com/articles/84786-cool-roofs-in-northern-climates?v=preview.

⁹Cool Roof Energy Savings Tool. GAF. Web. 10 August 2017. cool.gaf.com.

¹⁰Mackey, Christopher W.; Lee, Xuhui; and Smith, Ronald B. “Remotely sensing the cooling effects of city scale efforts to reduce urban heat island.” Building and Environment. March 2012. Web. 10 August 2017. www.sciencedirect.com/science/article/pii/S0360132311002472.

¹¹Sharma, A.; Conry, B.; Fernando, H.J.S.; Hamlet, Alan F.; Hellmann, J.J.; and Chen, F. “Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model.” Environmental Research Letters. IOP Science. June 2016. Web. 10 August 2017. iopscience.iop.org/article/10.1088/1748-9326/11/6/064004/meta.

¹²Zimmerman, Greg. “Do Cool Roofs Fit in Cool Climates?” Building Operating Management. March 2004. Web. 10 August 2017. www.facilitiesnet.com/roofing/article/Do-Cool-Roofs-Fit-In-Cool-Climates-Facilities-Management-Roofing-Feature--1526.

¹³Dregger, Phil. “Cool Roofs Cause Condensation: Fact or Fiction?” Western Roofing. March 2013. Web. 10 August 2017. rci-online.org/wp-content/uploads/2013-03-dregger.pdf.

GAF is the leading roofing manufacturer in North America and part of the largest roofing and waterproofing business in the world. Products include roofing and waterproofing solutions for residential and commercial properties and for civil engineering applications. Its portfolio is supported by a national network of factory-certified contractors. www.gaf.com/aia