Cool Roof Resources

There are thousands of product options just for cool roofing (including Conklin), so specifying an appropriate roof can be a daunting task. Cool roofs are available in all colors for virtually every roofing type, although white is still the most efficient option.

You can gauge the energy performance abilities by understanding how a cool roof reflects and emits the sun’s heat back to the sky instead of transferring it to the building below. Once you understand the basic technology of cool roofing, there are several resources available to help you make a confident, informed decision on your next project.

Solar reflectance and thermal emittance are the two key metrics determining how “cool” a roof will stay by its ability to reflect solar energy and emit absorbed heat. Solar reflectance and thermal emittance will appear as a value between 0 and 1, with a higher value signifying a “cooler” roof. Solar Reflectance Index (SRI) is a third metric that is calculated using a product’s solar reflectance and thermal emittance values. It is measured on a scale of 0 to 100 with a higher number symbolizing a more energy-efficient roof. SRI is sometimes used by code bodies or green building programs in place of solar reflectance and thermal emittance as a single-value alternative. Cool roof standards often specify higher reflectance requirements for low-slope, flat rooftops versus steep-slope, pitched rooftops. This difference in values is due to the energy impact the surface type faces, as the flat surface of a low-slope rooftop is exposed to greater solar radiation than a pitched roof.

Another factor in which roofing products are unique is that they are exposed to outdoor conditions that may alter the energy performing ability of the product. Each product is therefore tested initially as available straight off the shelf, as well as after it has been weathered by outdoor elements. A study by the Oak Ridge National Laboratory and DLR consultants found that the loss of effectiveness of solar reflectance for most roof types leveled out at around three years, so it is an industry standard to test roofing materials after three years of aging to determine their aged value. Code bodies sometimes reference this aged value, as it more accurately reflects the performance of the roof through its life cycle.

The Cool Roof Rating Council (CRRC) is a third-party rating program that works with manufacturers to rate their products’ solar reflectance and thermal emittance. The Rated Products Directory is a free online database of roofing products rated by the CRRC. Code bodies and voluntary green building programs define a cool roof by specifying a minimum value for initial and aged solar reflectance, thermal emittance and SRI, or a combination thereof. The CRRC does not set minimum standards for products to be listed on its Rated Products Directory, but provides unbiased and credible ratings for all products. You can search through more than 2,000 products by categories such as material type, color or manufacturer. You can even search by minimum initial or aged solar reflectance, thermal emittance or SRI value in order to fine-tune your search to products that meet a specific code or program standard.

While code bodies set cool roof minimum standards as guidelines, many people find it more realistic to specify a cool roof based on quantifiable benefits. The U.S. Department of Energy (DOE) and the Environmental Protection Agency (EPA) have both created cool roof calculators to determine energy and monetary savings based on climate, building size, HVAC equipment and other important factors.

• The DOE Cool Roof Calculator offers savings estimates for small- and medium-sized facilities with flat roofs.
• The EPA Roof Savings Calculator is designed for both residential and commercial buildings, and it allows you to define information about your existing and proposed roofs for comparison.

The cool roof calculators show the tangible savings gained from cool roofs, yet cool roofs offer several other environmental benefits. Eco-conscious designers may also want to consider the cradle-to-cradle aspects of their material choices, including recycled content, end of life recyclability and toxicity of materials.

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Measuring Weathered Cool Roofs, Updated DOE Roof Savings Calculator

A 2010 Lawrence Berkeley National Laboratory study showed that the average annual savings when substituting a .55 weathered reflectance cool roof for a .20 weathered reflectance gray roof is 5.02 kWh per square meter of roof surface. The study also showed that the savings are greater in areas of the country with higher air conditioning loads where an upper range benefit of 7.69 kWh per square meter was possible.

Cool roofs having the greatest benefit in air conditioning-heavy climates makes logical sense, and is in line with an important change to the most recent version of the ASHRAE 90.1 energy code, making cool roofs a prescriptive requirement for Climate Zones 1 through 3. Roofs in those areas — the South, Southwest, and most of California — that adopt the code must install roofs with a minimum three-year weathered reflectance of .55, and three-year weathered emittance of .75. Infrared emittance is the measure of how much radiation a surface re-emits to the atmosphere.

Using weathered results, as opposed to new, represents a shift in the industry in how cool roof effectiveness is measured, as well. New cool roofs can exhibit reflectance numbers as high as .75 or .80. Energy Star labels roofing products with initial reflectances of .65 on low slope roofs. The industry is beginning to understand that the true measure of how well the roof will perform depends not on its initial reflectance number, but on its weathered. Every cool roof gets soiled and loses performance over time, so it's very important to base energy calculations on aged value, not new.

That is exactly what the Department of Energy Roof Savings Calculator does, and allows you to enter several variables such as area of the country, building type, heat and cooling type, efficiency, as well as characteristics of your existing roof and proposed cool roof including weathered reflectance and emittance ratings. The resulting calculation shows the potential annual energy savings (or loss) with a cool roof.

According to André Desjarlais, group leader of the Building Envelope Program at Oak Ridge National Lab, the calculator was relaunched late last year to accomplish a few goals:

• First, it combines two calculators into one (previously, the Environmental Protection Agency (EPA) and DOE each had its own cool roof calculator). These two calculators were programmed with slightly different assumptions and therefore gave different results. The new calculator combines research and analysis from both agencies to be more comprehensive.
• Second, it's more sophisticated than either of the previous two in terms of how it allows you to enter data about a facility (basically, there are more variables - the old calculators didn't specify a building type, they assumed the roof was floating above space, etc. and now the calculator is more sophisticated and thorough to cover more scenarios).

Part of DOE's Cool Roofs Roadmap is to expand and improve the Roof Savings Calculator and to benchmark its results against actual experimental data. Another part of the plan is to study several different types of roofing, such as vegetative roofs and roof coatings like those from Conklin, to determine energy savings potential.

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Selecting The Right Roofing Products - Climate Considerations

The amount and type of precipitation, temperature and wind are the aspects of climate that should most affect the design and selection of the roof system for a building.

A building located in a dry climate like the desert southwest does not need the same type of roof as a building subjected to daily rains like in the pacific northwest. Places that have high fees for wastewater removal may want to consider a vegetated roof to absorb stormwater. However, rain isn't the only consideration. Snow can drift and collect in corners, topping flashings and cause leaks. Hail can puncture the roof system, requiring a roof that can withstand abuse. If there is a wide temperature spread between winter and summer, a roof system that will expand and contract with thermal movement is a good choice.

Climate also affects the amount of insulation needed. Predominantly hot areas should consider a reflective roof system to save on cooling costs. In mostly cold climates, energy savings depend on the cost of heating energy compared with cooling, the slope of roof, insulation, and overall building dimensions. One resource to determine whether a roof will have energy benefits is the Department of Energy's Roof Savings Calculator. Heat sinks may also be considered for hot climates to lessen the amount of thermal shock that can occur when a roof is suddenly cooled during a rainstorm.

Identifying the wind uplift requirements is important in areas prone to hurricanes or other high wind events. Anywhere the wind gusts more than gale force should take wind into consideration (even a 40-mile-per-hour wind can cause a poorly attached roof to peel).

Tomorrow we will discuss considerations for selecting the right roofing products from the building owner's perspective.

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Cool Roofing at The Ohio State University?

The sheer size and power of The Ohio State University is certainly something to brag about. However, one thing people are not bragging about is the amount of money spent on the energy used to maintain temperatures throughout campus buildings.
As everyone scrambles to find ways to reach carbon neutrality, they may be forgetting to simply look up. By using the U.S. Department of Energy Roof Calculator, converting the University’s roofing to “cool roofing” would not only save $60,000 annually, but also over 1.5 million pounds of carbon each year.

What exactly is cool roofing? It is a type of roofing that increases the amount of sunlight reflected, allowing the roof and building to stay cooler. It comes in various colors but the most iconic, popular and effective is white.

Costing the same or less as normal roofing and having similar life spans, there is no reason not to use this roofing technology. By reflecting more sunlight, the campus roofing saves money, energy and carbon by lowering air conditioning bills.

The University could install a cool roofing system like those from Conklin on Kottman Hall (which desperately needs a new roof) as a trial run and case study. Once the savings are realized, the University could then make a commitment to use cool roofing when replacing future roofs. There is no better place on campus to be a leader in sustainability than Kottman Hall, as it is the home of the School of Environment and Natural Resources.

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Cool Roofing, UPS and Energy Secretary Steven Chu

If you’re not friends with Steven Chu on Facebook, you missed the Energy Secretary’s recent post about a white-topped UPS truck spotted in the nation’s capital. “An encouraging sight drove past my office last week—a UPS delivery truck sporting a white roof,” Chu wrote. “If UPS can set aside its trademark brown color scheme for the sake of a cooler cargo area, hopefully more businesses and consumers will begin to ask themselves: ‘What can white roofs do for you?’”

The answer to that question is that a white, or "cool" roof could potentially lower the surface temperature of your roof by up to 100°F. That's according to the California Energy Commission, which estimates that cool roofs can trim cooling costs by 20 percent on average in the state.

Cool roofs work by reflecting sunlight. Painting the roof white is one approach. Installing light-toned asphalt shingles or clay tiles with a reflective coating like those from Conklin can also redirect the sun’s energy. But cool roofs aren’t for everyone. Those in hot, sunny climate where air conditioning is used a lot will reap the biggest benefits. In other regions, a cool roof could end up increasing heating costs in the winter, so you should use the Department of Energy’s cool-roof calculator to see how much energy you’ll save.

Please also see the June 2011 consumerreports.org article by Daniel DiClerico titled "Secretary Chu makes a friendly plea for cool roofs"

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Cool Roofs In Cool Climates

Even though cool roofing remains a hot industry trend, the science behind cool roofs - things like infrared emissivity and solar reflectance, isn’t exactly top on mind for facility executives researching roofing options.

To most people, cool roofing is a cut-and-dry issue: Roofing systems like those from Conklin that reflect the sun’s rays can save energy (and thus, money) in warm climates year-round and during hot summer months in more seasonal climates. Less clear and more controversial is whether cool roofing is beneficial in climates where, over the course of a year, heating energy loads dominate cooling. In other words, can cool roofs be advantageous in cold climates?

The answer to that question begins with a more complete picture of how a cool roof functions. “A cool roof is a roof that combines reflectivity and infrared emittance to keep the roof temperature cool,” says Andre Desjarlais, program manager for the Building Envelope research program at the U.S. Department of Energy’s Oak Ridge National Laboratory.

• Reflectivity is a measure of the percentage of solar radiation that is reflected when it strikes the roof surface.
• Infrared emittance, or emissivity, is a measure of the amount of remaining solar radiation that is released from the roof surface to the sky.

Solar radiation is made up of three forms of energy: about 5 percent ultraviolet, 45 percent visible light, and 50 percent infrared. When that energy strikes a roof, it is dealt with in several ways. For cool roofs, the largest portion is reflected, but energy is also emitted as infrared energy to the atmosphere. The energy that is absorbed and converted to heat is transferred through convection with the air directly above the surface, and the remaining heat is conducted into the building.

Most industry experts agree that reflectivity has a greater impact than emissivity on the energy performance of the roof during hot weather. If a majority of the initial solar radiation is reflected, then a smaller portion is left for infrared emittance. Many cool roofs have reflectivities of 75 to 80 percent, or 0.75 to 0.80, which means that only 20 to 25 percent of the sun’s energy is absorbed into the roof.

According to Lawrence Berkeley National Laboratory (LBNL), at an ambient temperature of 98 degrees, raising a roof’s reflectivity from 0.25 to 0.40 while keeping emissivity constant results in a surface temperature reduction of 13 degrees. A change in a roof’s emissivity from 0.75 to 0.90 while keeping reflectivity constant results in a surface temperature reduction of only 2 degrees.

The combination of high reflectivity, usually a result of light-colored or white surfaces, and high emissivity during hot summer months results in a surface temperature sometimes as much as 60 to 70 degrees cooler than a non-reflective roof. With less net heat energy to deal with, the air conditioning system doesn’t have to work as hard to keep the building at a comfortable temperature.

While the reflective and emissive properties of a roof are most important for its coolness, other factors such as insulation, roof orientation and roof pitch contribute to a building’s overall thermal efficiency. “Building owners should never agree to a roof based solely on the fact that it’s a white roof,” says Jared Blum, president of the Polyisocyanurate Manufacturers Association and a board member of the Solar Smart Roof Alliance.

Some of the long-term performance issues of roof selection should also be considered, including maintenance costs, such as power washing or recoating, that might be necessary to keep the roof performing as it did when it was initially installed. Another consideration is a roof’s long-term ability to match functionality with aesthetics.

But even if the roof is kept in mint condition, the question remains of whether the cool roof will be a thermal detriment in a heating-dominated climate.

“The ideal roof would be 100 percent reflective in the summer and 100 percent absorbent in the winter,” says Art Rosenfeld, California Energy Commissioner. Unfortunately, a roof can’t change its reflective and emissive properties, so the general energy efficiency of a cool roof must be assessed by comparing the energy saved during the hot summer months to the energy consumed, or the “heating penalty,” during the heating season.

Skeptics of the energy benefits of cool roofs postulate that in cold climates, such as Minneapolis or Chicago, where heating degree-days vastly outnumber cooling degree-days, the heating penalty would be severe enough to render a cool roof counterproductive.
Heating and cooling degree-days are measures of the number of degrees the average daily temperature falls below or above 65 degrees. For instance, if the average temperature for a 24-hour period is 23 degrees, that day chalks up 42 heating degree-days. The main purpose of heating and cooling degree-days is to serve as an index of heating and cooling energy loads over defined time periods. But they also help determine whether certain building strategies are appropriate for a particular geography.

This use was the impetus behind their inclusion as variables in the development of calculators that predict how much energy and, by extension, how much money per square foot would be saved with the use of cool roofs vs. non-reflective roofs in specific locations. The calculators, developed separately by the U.S. Environmental Protection Agency and the Department of Energy’s Oak Ridge National Laboratory, allow users to enter the thermal properties of the proposed roof, amount of insulation, cost of energy and efficiency of the building’s HVAC systems, among other things.

The calculators are not meant to be precise indicators of specific building performance. Rather, they help give a general indication of how certain roofing materials with specific thermal properties will perform in various parts of the country. In other words, they can help settle the argument, from strictly an energy usage and monetary perspective, whether cool roofs can be beneficial in cold climates. In many cases, even in the cold climates, the calculators still yield a yearly net savings for using cool roofs.

There are at least five reasons why the heating penalty in the winter time isn’t nearly as severe as it could be and why the summer cooling savings, to some degree, are able to counteract the winter heating penalty in cold climates:

1. During the winter, the solar angle is lower so reflectivity and absorption aren’t as important. Reflectivity and absorption are more critical during the summer when the sun is higher in the sky and solar radiation is hitting the roof directly.
2. The days during winter months are shorter so less total energy is hitting the roof to be absorbed or reflected over the same period of time as during the summer.
3. The ratio of cloudy to sunny days increases during the winter, so again, not as much solar energy is striking the roof.
4. Snow piled up on the roof during parts of the winter reflects the sun’s energy. Therefore, it doesn’t matter how reflective or absorbent the roof is.
5. In many cases, resources cheaper than electricity, such as natural gas or oil, are used to heat buildings in the winter.

Still, in far northern climates like Chicago, the actual savings, strictly in terms of energy use, if any, might be fairly minor, says Desjarlais.

The debate doesn’t end there, though, as cool roofs in seasonal climates can be beneficial for other reasons. That’s because cool roofs can have more impact on energy costs than energy use. Cool roofs cut energy use during peak demand times during summer when rates are highest. What’s more, cool roofs can help reduce the demand charge that a facility pays all year on the basis of its greatest energy use. Additionally, some northern utility companies offer rebates and incentives for tactics like cool roofs that help facilities cut down on the peak demand load. The idea is to help ensure that there will be enough energy to go around, thus avoiding brownouts.

“The peak demand benefits of cool roofing are the same no matter how far north you march,” says Desjarlais.

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

“The only building that won’t benefit from a cool roof energy-wise is one that’s not air-conditioned,” says Hashem Akbari, staff scientist and group leader for Lawrence Berkeley National Laboratory’s Heat Island Group.

Akbari’s group also researches measures cities can adopt to mitigate the urban heat island effect, another area in which cool roofs are invaluable, even in seasonal climates. The urban heat island effect is a phenomenon wherein dark building materials, dark pavement and lack of vegetation create a 6 to 8 degree difference between downtown areas of major metropolitan cities and outlying suburban areas. The elevated temperature means that cities as a whole and buildings specifically consume more cooling energy. Additionally, as the air temperature increases, air quality decreases, putting people at further risk for smog-related health problems.

Because of the lower roof surface temperature on roofs with a high emissivity and high reflectivity, urban heat islands can be reduced with widespread use of cool roofs. This is true even in cities with seasonal climates. A study performed by Akbari and his team in Toronto shows that if heat-island-reducing measures, including cool roofs, were adopted widely, the city could save more than $10 million a year on energy costs.

On a national level, widespread adoption of cool roofs, independent of other mitigation measures, could save close to $750 million in energy costs in major urban areas, LBNL estimates.

“It’s a collective thing for building owners,” says Greg Crawford, executive director of the Cool Metal Roofing Coalition. “If several buildings begin installing reflective roofs, it will lower the temperature of the urban area and reduce the natural load on building systems.”

Please also see the March 2004 facilitiesnet.com article by Greg Zimmerman titled "Do Cool Roofs Fit In Cool Climates?"

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Reflective Coatings for Asphalt Roofs

If you spend more money and energy on cooling than on heating, you can cut this summer's air conditioning bills by investing in a reflective roof coating.

The main options for coating an asphalt roof are white polymers (like those from Conklin) and asphalt-like resins with reflective aluminum flakes. Both are reasonably priced, and offer short payback periods.

Why use a reflective roof coating?
Flat asphalt roofs reach up to 200 degrees Fahrenheit and absorb up to 70% of the solar heat blasting onto the building. By contrast, the best reflective roof coatings reflect up to 80% of solar heat, and can reduce surface temperatures on a roof by 80 degrees.

This can cut internal building temperatures by up to 10 degrees, increase the effectiveness of the insulation, and cut cooling energy costs by 25-70%. It also makes the building more comfortable in hallways or other areas that may not be air conditioned, and the roof will last longer without as much heat-related cracking and deterioration, saving money and materials in the long run.

White Reflective Roof Coatings
High-quality white polymeric coatings like those from Conklin are made with acrylics or similar materials mixed with an opaque, white and reflective pigment. They are probably the most effective reflective coating for the majority of asphalt roofs. There are also polymeric coatings that are tinted for aesthetic reasons, but they are less reflective and therefore won't save as much energy.

Tests at Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory showed white elastomeric coatings offer about 60% solar reflectance, leaving the roof temperature 36 degrees higher than the ambient air temperature - a much smaller difference than that generated by a black asphalt roof. All polymeric coatings must be chosen and applied carefully, particularly on rough asphalt roofs.

Aluminum Reflective Roof Coatings
Metallic reflective coatings may be better for some rough asphalt roofs. They use asphalt-like resins and other materials mixed with aluminum flakes. The aluminum rises to the surface of the coating as it sets, creating a solid, reflective surface. Metallic coatings are rated at 55% reflectance, which is similar to the elastomeric coatings. But aluminum typically has higher average temperatures than elastomeric-coated roofs. The aluminum retains heat more than elastomeric coatings.

Calculate Your Savings
The federal government does not offer energy savings rebates for reflective roof coatings, but you can look for Energy Star-rated roof coatings, which guarantee a minimum level of reflectance.

Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory also have a roof savings calculator. It uses weather data and your building information to estimate the cost of a new roofing system or coating, and the potential energy savings. The calculation tool is in the beta phase and is not fully automated. After you plug in data, the lab will email you results.

Again, buildings in hot climates and heavily use air conditioning will benefit in comfort and energy savings from a reflective roof coating like those from Conklin.

Please also see the May 2010 networx.com article by Steve Graham titled "Reflective Coatings for Asphalt Roofs"

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ROOFING CONTRACTORS NEEDED IN MULTIPLE STATES!
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