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.

Stanford Hospital Project Demands Versatility and Surgical Precision

The new Stanford Hospital is currently under construction in Palo Alto, Calif. The 824,000-square-foot facility connects to the existing hospital by a bridge and tunnel. The project includes a multi-level parking garage and with additional office buildings. Photo: Stanford Health Center.

The new Stanford Hospital is currently under construction in Palo Alto, Calif. The 824,000-square-foot facility connects to the existing hospital by a bridge and tunnel. The project includes a multi-level parking garage and with additional office buildings. Photo: Stanford Health Center.

Dennis Olson is used to dealing with large health care projects with multiple scopes of work, but the new Stanford Hospital project he’s currently working on might be the most challenging job he’s ever faced.

“I’ve never been involved with a project that’s been this complex and this difficult to roof and manage,” says Olson, the owner of Letner Roofing in Orange, Calif. “There are 16 different types of roofing and waterproofing systems, and each one is a little bit different at each location around the building.”

Located in Palo Alto, Calif., the new Stanford Hospital is an 824,000-square-foot facility that connects to the existing hospital by a bridge and tunnel. Olson is convinced his company is perfect for the job. He has been in the roofing industry for almost four decades, and he’s worked at Letner for more than 30 years. Olson worked his way up through the company as a foreman, project manager, and estimator before becoming the president and owner 15 years ago. “I have been estimating and managing health care projects for more than 25 years,” he says. “This job is right up our alley.”

The Company

Located in Orange, Calif., Letner Roofing specializes in commercial work including all types of roofing and below-grade waterproofing systems. “We are licensed with all of the major manufacturers to install their products,” Olson says. “We install basically every roofing and waterproofing system that’s available to the market. We have a sheet metal division that produces metal wall panels, roofing and general sheet metal.”

The new hospital features green roofs on the main hospital, central plant and parking structure. The garden roof section on level three of the main hospital building is shown here. Photo: Stanford Health Center.

The new hospital features green roofs on the main hospital, central plant and parking structure. The garden roof section on level three of the main hospital building is shown here. Photo: Stanford Health Center.

Olson believes the company’s success begins with its great alliances with top general contractors and owners. “Our strengths are our customer service and quality control, and our ability to get projects done efficiently and on time,” he says. “I think that’s why general contractors choose us. We do what we say we’re going to do, we do it efficiently, and we take a lot of pride in the finished product.”

Communication is the key, according to Olson. “We have weekly sales meetings where all of the project managers and sales staff get together,” Olson says. “We share information, which allows us to learn from our failures and successes. It’s a team atmosphere. There is no real competition between the sales guys other than the innate competition that you each have to be better. We don’t compete against each other; we all work together for the common goal.”

Keeping the lines of communication open with industry partners is a key part of the puzzle. “As far as communication with the general contractor, that’s pretty simple, but a lot of people miss that,” he says. “You have to return phone calls. You have to return emails. If you have an issue on a project, handle the issue efficiently. Bring scheduling problems or details issues to the attention of the general contractor early. Nobody like to be surprised. People like to be informed.”

Due to their expertise in design-build situations, members of the Letner team are often called in by general contractors at the design and budgeting stage to offer advice on the right materials and methods for a project.

That was the case with the new Stanford Hospital project and general contractor Clark/McCarthy—a joint venture of Clark Construction Co. and McCarthy Building Cos. “McCarthy is a contractor I’ve been dealing with for more than 25 years. I’ve done a lot of health care projects with them, so when Stanford came out, they certainly wanted our input and help developing the budgets,” notes Olson.

Underground, Overhead

For Letner, the project involved several scopes of work including roofing on the main hospital and below-grade and underslab waterproofing.

Below-grade work included a pre-applied blind-side waterproofing application by Cetco. Letner also waterproofed underground tanks for domestic water, fire suppression, and sewage with a hot rubber system by Gaco Western. “The hospital was built for the worst-case scenario,” Olson notes. “If there is a big earthquake, and services are interrupted, the hospital can sustain itself for a while.”

This aerial photo shows the new Stanford Hospital, which is currently under construction. When completed in 2018, the complex will showcase 16 different roofing systems on 12 different elevations. Photo: Stanford Health Center.

This aerial photo shows the new Stanford Hospital, which is currently under construction. When completed in 2018, the complex will showcase 16 different roofing systems on 12 different elevations. Photo: Stanford Health Center.

As the superstructure was being completed, the roofing work began. “As I said, there are 16 different roofing systems on this project. There are 12 different elevations,” notes Olson.

Systems range from urethane and urethane and polymethyl methacrylate (PMMA) coatings to split-slab and inverted hot rubber systems, PVC roof systems and hybrid dual waterproofing system. The largest roofing systems include a Sarnafil PVC roof on the main hospital and a hot rubber system by Cetco for use under the garden roofs. Letner is installing garden roofs on the third floor of the main hospital and another on the central plant building.

Both of these garden roofs were constructed over flat concrete decks. The first step was to provide positive slope for drainage. Cell-Crete Corporation of Hayward, Calif., provided lightweight insulating concrete (LWIC), which was used to create positive slope. After the LWIC cured, crews from Cell-Crete installed quarter-inch cement board over the LWIC.

The hospital’s surgery rooms are directly beneath the garden roof on the main hospital, so the system has to be bulletproof. “This roof area requires intricate detailing along with a Cetco hybrid dual waterproofing system,” Olson states. “After the lightweight concrete and cover board are in place, Letner will install 60 mils of Hydrofix urethane membrane, followed by Cetco Corflex, a unique combination of a re-enforced KEE membrane bonded to an active polymer core membrane. Both garden roof areas will be protected with an in-place leak detection system by Internal Leak Detection.”

The overburden at the hospital garden roofs will include insulation, drainage mats, various types of plants and trees and pedestal paver systems.

Letner installed PVC roof systems from Sika Sarnafil level three of the hospital and on the main roof of the hospital. The 60-mil PVC membrane was installed over insulation and DensDeck cover board. Insulation was a minimum of R-20 near the drains. Some sections of the PVC were topped by ballast rock.

On the adjoining multi-level parking deck, Letner installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing of Irvine, Calif.

Safety Precautions

Letner and the general contractor help ensure safety is always top of mind at the site. “On this project, like any other, the safety issues were extremely important,” notes Olson. “We have our crews stretch and flex daily, and everyone must wear the personal protective equipment required for each task. Fall protection is a concern at every elevation, and hot rubber is extremely hazardous activity that requires additional protection and monitoring.”

Elastizell lightweight insulating concrete from Cell-Crete was used to provide slope for drainage on the flat structural concrete decks. It was later topped with cement board. Photo: Cell-Crete

Elastizell lightweight insulating concrete from Cell-Crete was used to provide slope for drainage on the flat structural concrete decks. It was later topped with cement board. Photo: Cell-Crete

The perimeter walls were being constructed during the project, so extra precautions had to be taken at the roof edge. “We had to wear harnesses and be tied off at all times,” Olson says. “We are very concerned about safety. We have a safety manager, and he does a very good job of identifying possible hazards on each job. We identify those per deck and apply the proper safety measures required for each elevation.”

Waterproofing the tanks also required special care. “The domestic water, waste and fire tanks and are in the ground, so you have to have people certified to do that work with specialized equipment,” Olson states.

Challenging Schedule

Construction of the hospital is still underway. Work is expected to be completed in 2018. The sheer size and multiple scopes of work were obvious challenges on the project, but the schedule was also tight—and subject to change. Some roof details were changed and others were developed as the job progressed, so Letner’s crews had to make some adjustments on the fly. Letner continues to work with the consultant on the project, ABB, to iron out the details.

“Sometimes you have to adjust the schedule when you are coordinating the work with other trades,” Olson notes. “The schedule, coordinating with other trades and the number of changes on the job have been the biggest issues we’ve faced. It’s is still a challenge, as the work is ongoing.”

When it came time to stage equipment and materials, the large job site suddenly seemed small. “The site was kind of tight, so of course logistics came into play with loading and off-loading each different area,” he says. “Some areas were hard to get to, and sometimes we had to wheel the product through corridors to get to the decks. Not everything was easy to get to. Logistics were difficult, but we were able to overcome those problems. Clark/McCarthy helped out quite a bit with logistics and loading.”

Despite the complexity of the job, the installation work has gone smoothly, according to Olson. “As far as the application for our field crews, there’s not that much difficulty for them. They are all very talented at what they do,” he says. “It’s just a very difficult building, and there are a lot of details that are not typical.”

The key to overcoming difficulties? “It’s constant communication,” Olson says. “Our strengths are our management teams, from the field operations to office staff. We’re honest with our customers. They understand the level of customer service and quality we deliver. Our success is a testament to the service we provide to our customers. We are often praised for our service and workmanship, and we are very proud of our quality installations as well.”

On the adjoining multi-level parking deck, Letner Roofing installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing. Photo: Stanford Health Center.

On the adjoining multi-level parking deck, Letner Roofing installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing. Photo: Stanford Health Center.

TEAM

Architect:
Rafael Viñoly Architects in association with Lee, Burkhart, Liu Inc.

General Contractor:
Clark/McCarthy—a joint venture of Clark Construction Co. and McCarthy Building Cos.

Roofing and Waterproofing Contractors:
Main hospital building and offices: Letner Roofing, Orange, Calif.
Adjoining parking structure: Courtney Waterproofing and Roofing, Irvine, Calif.

LWIC Provider and Installer:
Cell-Crete Corp., Hayward, Calif.

Walkable Roofing Membrane Features Aggregate Pebble Look

Pebble Beach brings an aggregate pebble appearance to outdoor spaces in a simple, one-step application while maintaining the reliable, low-maintenance waterproof protection.

Pebble Beach brings an aggregate pebble appearance to outdoor spaces in a simple, one-step application while maintaining the reliable, low-maintenance waterproof protection.

Duradek, the original Walkable Roofing Membrane expands its response to market demands for naturally inspired textures and colours for outdoor living space in its addition to the LEGACY line with the “Pebble Beach” designer aggregate pebble look in a 60-mil vinyl membrane.

Duradek, a brand of pedestrian traffic waterproof membranes features the trend of a natural stone look on low-maintenance vinyl outdoor walking surfaces by introducing Pebble Beach, an addition to the ‘Legacy’ line of PVC membranes.

Pebble Beach brings an aggregate pebble appearance to outdoor spaces in a simple, one-step application while maintaining the reliable, low-maintenance waterproof protection.

Snow-retention System Is for TPO and PVC Membranes

Sno Gem Inc. introduces the Sno Barricade TPO and PVC Membrane Deck Mount Bar snow-retention system.

Sno Gem Inc. introduces the Sno Barricade TPO and PVC Membrane Deck Mount Bar snow-retention system.

Sno Gem Inc., a snow-retention system manufacturer, introduces the Sno Barricade TPO and PVC Membrane Deck Mount Bar snow-retention system. It is a membrane-coated and pre-skirted continuous-bar snow system (patent-pending) for new construction or retrofit applications.

The base plates are custom-coated in either TPO or PVC with a standard white, gray or black. Custom colors are available to match the roofing membrane. To ensure an easy installation, Sno Barricade Membrane-Coated Diamond Series System is available with a pre-skirted target patch, heat-welded directly to the TPO- or PVC-coated base plate. Installers can heat-weld Sno Gem’s target patch to the membrane of the roof, reducing labor cost on a watertight system.

Sno Barricade Systems are available in 1- or 2-inch bar size with single, double or triple bar retention. Square or round bars are offered to best match a building’s aesthetics. The Sno Barricade Plate, an accessory to the system that prevents snow and ice from sliding under the bars, is available in mill finish or custom colors.

Carlisle SynTec Systems Achieves IRE Best New Product

Carlisle SynTec Systems’ Sure-Flex KEE HP PVC was honored with the Best New Product award at the 2014 International Roofing Expo Product Showcase. A panel of industry experts selected Carlisle’s KEE HP PVC as the roofing industry’s Best New Product for its excellent performance characteristics.

Carlisle’s KEE HP PVC membranes contain a solid KEE HP (high-performance) plasticizer with a higher molecular weight than standard KEE. Featuring improved aesthetics, enhanced thermal performance, a wider window of weldability and superior cold temperature flexibility, KEE HP PVC is an ideal roofing membrane for virtually any job. KEE HP membranes also offer a high level of resistance to chemicals, microbial growth and dirt pickup.