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.

Metal Barrel Roof Tops the Rebels’ New Basketball Arena

The Pavilion at Ole Miss seats 9,500 fans.

The Pavilion at Ole Miss seats 9,500 fans. The building’s signature is its standing seam metal roof, which was manufactured by ACI Building Systems. Photos: Professional Roofing Contractors Inc.

The Pavilion at Ole Miss is a multi-purpose facility that is most famous for hosting the University of Mississippi’s basketball team. The arena cost approximately $97 million to build and seats 9,500 fans. The building’s signature arched metal panel roof was designed to complement the curved entrance and blend in with other architectural features on the university’s campus in Oxford, Miss.

Professional Roofing Contractors of Shelbyville, Tenn., was originally called in to assist with estimating the cost of the structure’s main roof, as well as a membrane roof system on the lower level. Upon final bid results, the decision was made to proceed with a standing seam metal roof on the upper portion of the building and a PVC roof on the lower level. Professional Roofing was the successful low roof bidder and selected ACI Building Systems to provide the standing seam roof materials and Sika Sarnafil to provide the PVC membrane roof materials. Professional Roofing installed both systems, with Jose Martinez as the crew leader for the membrane roofing portion and Dale Jones in charge of the metal roofing crew.

Larry W. Price, president of Professional Roofing, and Jonathan Price, the company’s vice president and the production manager on the project, oversaw the installation of 79,500 square feet of standing seam metal roofing and 46,500 square feet of PVC. There wasn’t much room for staging material on the jobsite, which didn’t give the company much room to maneuver. For the main roof, bundles of pre-cut metal panels were trailered in by ACI and loaded to the roof by crane.

“Logistics were complicated,” notes Larry Price. “Just getting a big enough crane in there and lifting the panels was difficult. Once we got the panels on the roof and they were situated, the roofers could just move ahead.”

Photos: Professional Roofing Contractors Inc.

Photos: Professional Roofing Contractors Inc.

Panels were installed with a 2-inch-high, double-lock standing seam, which was completed using a self-propelled mechanical seamer from D.I. Roof Seamers. The metal panels were curved into place by crews on the roof, who installed them over the staggered metal deck after it was covered with two 2-inch layers of polyiso insulation and Carlisle’s WIP 300 HT self-adhered underlayment. “The metal deck was segmented,” notes Jonathan Price. “We had to bridge some of those sections to make a nice, smooth curve.”

The scope of work included a large gutter at the roof edge. The gutter was 3 feet high and 2 feet wide, and crews from Professional Roofing flashed the gutter and lined it with the same Sika Sarnafil PVC used on the lower roof.

On the mezzanine level, crews installed a vapor barrier and mechanically fastened two 2-inch layers of polyiso insulation, as well as some tapered insulation for drainage. Once that work was completed, the 60-mil PVC was applied.

“Everything went pretty smoothly,” says Jonathan Price. “Logistics are usually tight on a new construction project, but once we adjusted to that, we just had to cope with the weather.”

“We had a lot of hot days and some rainy days,” Larry Price remembers. “Mississippi in the summer can get hot, hot, hot—and when it’s not hot, it’s raining.”

TEAM

Architect: AECOM, Kansas City, Mo.
General Contractor: BL Harbert International, Birmingham, Ala., Blharbert.com
Roofing Contractor: Professional Roofing Contractors Inc., Shelbyville, Tenn., Professionalroofingcontractors.com
Metal Roof Panel Manufacturer: ACI Building Systems, LLC, ACIbuildingsystems.com
PVC Roof Manufacturer: Sika Sarnafil, USA.sarnafil.sika.com

RoofPoint Administration Transfers to Roofing Industry Alliance for Progress

The Roofing Industry Alliance for Progress announces the administration of RoofPoint has been transferred to the Alliance. RoofPoint is a voluntary, consensus-based green building rating system that provides a means for building owners and designers to select nonresidential roof systems based on long-term energy and environmental benefits.

Originally developed by the Center for Environmental Innovation in Roofing and co-sponsored by the Alliance, RoofPoint is a roofing-specific version of a green building rating system that promotes an environmentally responsible built environment.

“The increasing need for energy efficient and environmentally friendly roof systems makes RoofPoint an important component of our industry,” says Alliance president, James T. Patterson C.P.M of CentiMark Corporation, Canonsburg, Pa. “We are pleased to have the opportunity to manage RoofPoint, and to continue the essential role it plays in promoting environmentally sustainable buildings.”

To ensure a smooth transfer of RoofPoint to the Alliance, a task force has been established to examine RoofPoint’s data and determine next steps.

Task force members are Rob Therrien, president of The Melanson Co. Inc., Keene, N.H.; Helene Hardy-Pierce, vice president of technical services, codes and industry relations for GAF, Parsippany, N.J.; Brian Whelan, senior vice president of Sika Sarnifil Inc., Lyndhurst, N.J.; Jim Barr, president of Barr Roofing Co., Abilene, Texas; and Mark Graham, vice president of technical services for the National Roofing Contractor Association (NRCA), Rosemont, Ill.

The task force will present its recommendations to the Alliance Board of Trustees during its Nov. 17 meeting in Chicago.

Projects: Education

University of Virginia, Rotunda, Charlottesville

The University of Virginia was founded by Thomas Jefferson in 1819.

The University of Virginia was founded by Thomas Jefferson in 1819.

TEAM

ROOFING CONTRACTOR: W.A. Lynch Roofing, Charlottesville
ARCHITECT: John G. Waite Associates, Albany, N.Y.
JOINT-VENTURE BUILDER: Christman-Gilbane, Reston, Va., ChristmanCo.com and GilbaneCo.com
LEAD-ABATEMENT CONTRACTOR: Special Renovations Inc., Chesterfield, Va.

ROOF MATERIALS

The domed roof required about 6 tons of 20-ounce Flat-Lock copper. W.A. Lynch Roofing sheared 4,000 individual tiles to approximate dimensions in its sheet-metal shop, and a makeshift sheet-metal shop was set up on top of the scaffolding to complete the final measurements and exact cuts.

COPPER SUPPLIER: N.B. Handy Co., Lynchburg, Va.
COPPER MANUFACTURER: Hussey Copper, Leetsdale, Pa.

ROOF REPORT

The University of Virginia was founded by Thomas Jefferson in 1819. Jefferson modeled his design—presented to the university board in 1821—after the Pantheon in Rome. Although he died in 1826 while the Rotunda was still under construction, the stunning building housed the university’s library as Jefferson envisioned.

The rotunda renovation is a two-phase project, and roofing work was part of Phase 1. The roofing team believed seven months was adequate to complete the job; the university, however, requested it be complete by April 2013 so scaffolding would be removed in time for the commencement ceremony. That gave the team a four-month timeline.

The domed roof required about 6 tons of 20-ounce Flat-Lock copper.

The domed roof required about 6 tons of 20-ounce Flat-Lock copper.

Tom McGraw, executive vice president of W.A. Lynch Roofing, explains: “This was just short of impossible even if it wasn’t winter. But as a graduate of UVA, I recognized the basis of the request and agreed to it. So we doubled the manpower and went to a 10-hour day, seven-day a week schedule. We divided the roof into four equal quadrants, each separated by an expansion joint and put a crew in each area working simultaneously with the other three. We also added support personnel in our sheet-metal shop, as well as runners to keep the flow of material to the job site on schedule for the sheet-metal mechanics. In the final analysis, we made the schedule and completed our work within the owner’s request.”

The roofing project was essential because of rust on the previous terne-coated metal roof. It was determined the rust was caused by inadequate roof ventilation that created condensation on the underside of the metal roofing. Ventilation was lacking because of a Guastavino tile dome that was installed in 1895. The condensation was addressed by installing a concealed venting system at the intersections of the treads and risers at the seven steps in the roof, as well as at the top of the dome below the oculus. “Heated air has low density so it will logically rise creating natural convection,” McGraw notes. “This convection creates air movement below the roof and minimizes dead air spaces and the potential for condensation. The key to this is ensuring that you size the ‘intake’ venting similar to the ‘exhaust’ venting so that air will flow in an unrestricted fashion.”

Reroofing a dome can be a challenge, and determining how to keep the interior and its priceless valuables dry required some ingenuity. McGraw invented a tarp that he compares to a hooped skirt to keep the space watertight. The roofing crew cut trapezoidal sections of EPDM membrane and installed them from the bottom to the top of the dome. This skirt-like tarp was configured out of eight pieces at the bottom, six at the midpoint and four at the top. The maximum cut sizes for each level were determined using a computer drawing. Creating the EPDM covering in sections made the tarp easy to handle and remove. “If we seamed it all together or made it in less pieces, the guys wouldn’t have been able to lift it,” McGraw adds.

The tear-off process involved removing the painted metal panels according to lead-abatement standards; the panels were cleaned offsite to maintain the integrity and safety of the job site. A new wood deck was installed on furring over the tiles. This was covered with 30-pound roofing felt and red rosin building paper followed by the new copper roof.

Each piece of copper was tinned and folded before being installed. This process was necessary because of the lack of symmetry on the building. McGraw recalls: “Because this building is almost 200-years old, you have to recognize that not everything is as true and square as one might hope. There are seven steps that circle the base of the dome, and each tread and riser changed in height and width all the way around the building.”

This is the fourth roof for the Rotunda. The first was a tin-plate roof designed by Thomas Jefferson; the second was copper that was a replacement roof after a fire in 1895; the third roof was painted terne-coated steel from 1976; and the current roof is 20-ounce Flat-Lock copper that will be painted white. The decision to select copper was based on cost, durability and historic appearance.

Phase 2 of the project began in May, and the Rotunda will be closed for repairs until 2016. At a price of $42.5 million, utility, fire protection and mechanical upgrades will be made, as well as a Dome Room ceiling replacement and construction of a new underground service vault. The roof also will be painted white, and leaking gutters will be repaired during this phase.

PHOTOS: DAN GROGAN PHOTOGRAPHY

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New Roof Must Last as Long as the Solar Panels It Supports

As thousands of Silicon Valley employees exited Hewlett-Packard (HP) global operations headquarters to head home for the evening, a crew of 25 roofers–under the glare of temporary spotlights–toiled diligently. They were fastening thousands of 1/2-inch DensDeck Prime coverboards to the 10-year-old insulation system covering the building’s metal deck.

Originally planned to be white, Hewlett-Packard ultimately selected a tan-colored membrane, to reduce glare because two levels of the building have glass-to-ceiling windows that allow visual access to the roof.

Originally planned to be white, Hewlett-Packard ultimately selected a tan-colored membrane, to reduce glare because two levels of the building have glass-to-ceiling windows that allow visual access to the roof.

Soon after, they adhered a single-ply, fleece-faced, tan-colored Sika Sarnafil EnergySmart roof membrane to the DensDeck Prime boards, creating a state-of-the-art 300,000-square-foot reroof. The added protection was much-needed, as it provided the durability and compressive strength to safely accommodate a massive system of solar panels that were installed atop 85 percent of the roof.

“We chose DensDeck Prime because it provides the best support for the new membrane, the existing roof and all the (solar) equipment that will go on top of it,” explains Steve Nash, vice president of Waterproofing Associates, who designed the reroof system in conjunction with Ted Christensen of Independent Roofing Consultants, and selected the materials to make it work. “With all the weight that will be bearing directly on the roof membrane, we need the ultimate roof substrate.”

Installing the massive, electricity-generating system of solar panels was an intricate endeavor, especially because its presence will complicate any repairs to the roof during the solar energy system’s anticipated 25-year life cycle. The building owner called on Nash to create a roof with a life cycle that would mirror the life of the solar panels.

The building owner desired a roof with a life cycle that would mirror the 25-year life span of the solar panels, which cover 85 percent of the roof.

The building owner desired a roof with a life cycle that would mirror the 25-year life span of the solar panels, which cover 85 percent of the roof.

“If the roof were to need repairs, the solar panels would have to be disassembled and out of service until the repairs are finished. And that can’t happen,” Nash adds. “Basically, we have to build a virtually maintenance-free roof.”

Protection—Above and Below

Cost-effective because of its energy efficiency and high levels of dimensional stability, the Sika Sarnafil G410 membrane is frequently installed over an underlayment of DensDeck Prime because its surface treatment provides a stronger bond for adhered membrane applications. Also, DensDeck Prime roof boards’ high pounds per square inch (PSI) compressive strength is an advantage as a durable platform for roofs with heavy equipment, like solar panels, on top.

Adding further complexity to the building’s new roofing system was the fact that the owner chose only to replace the original membrane—from another manufacturer—that had sprung a number of leaks in recent years. Keeping the remainder of the original roof—2 inches of fiberglass insulation, a built-up gravel surface and 1/2 inch of fiberboard—saved considerable time and money, as well as avoided having to send thousands of pounds of materials to landfills.

However, it did require adding the layer of DensDeck Prime to do double duty: carefully protect the layers of the original roof that would remain while forming the foundation for the Sika Sarnafil membrane.

Upon completion of the five-week project, which was conducted only at night and on weekends so the noise wouldn’t interrupt the HP employees during normal work hours, the new roof is aesthetically pleasing. Originally planned to be white, the owners ultimately selected a tan-colored membrane, to reduce glare because two levels of the building have glass-to-ceiling windows that allow visual access to the roof.

Nash notes the new roof’s beauty will only be exceeded by its durability. “With thousands of pounds of solar panels sitting on top of it, the roofing membrane cannot fail. So you get the best materials available to make it last—and that’s exactly what we’ve done.”