Cool Roofs Also Beneficial in Cold Climates

One of the goals of the U.S. Department of Energy's Cool Roofs Roadmap is to answer one of the most fundamental cool roof-related questions: Are cool roofs beneficial in cold climates?

Andre O. Desjarlais and P. Marc LaFrance both say they think so - if not from strictly an energy standpoint, then from the fact that they can help reduce the urban heat island effect.

"If you put a cool roof on a building in a cold climate and run the calculator strictly on energy, it may not save energy because of the heating penalty," says LaFrance. "But if you take into account the urban heat island effect, the indirect benefits may make cool roofs worthwhile."

This is often a tough sell for facility managers only worried about their own bottom lines. But research has already shown the effectiveness of cool roofs like those from Conklin at reducing urban heat islands, pollution and smog. For instance, the Heat Island Group at LBNL showed that Los Angeles spends about $100 million in extra energy costs to mitigate its urban heat island.

Reducing the temperature citywide means less air conditioning energy is required everywhere, which also means fewer greenhouse gas emissions. For this reason, many northern cities like Chicago, Philadelphia and New York City, have mandated cool roofs in their building codes. Utilities in northern states like Wyoming, Minnesota and Oregon offer rebates for the use of cool roofs. And the voluntary LEED rating system specifies cool roofs for a point explicitly for "urban heat island reduction." LaFrance says he hopes the research planned in the Cool Roofs Roadmap will more firmly establish a link between widespread use of cool roofs and reduced air conditioning energy use, pollution and greenhouse gas emissions.

One specific initiative, on which the Department of Energy is already working in conjunction with two other organizations (the White Roofs Alliance and Local Governments for Sustainability), is called the 100 Cool Cities initiative. DOE hopes to engage 100 cities around the world to commit to widespread installation of reflective surfaces by 2020. New York City, Taipei and Athens were the first three cities to sign up.

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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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U.S. Secretary of Energy Steven Chu: Cool Roofs Like Removing All Cars for 11 Years

U.S. Secretary of Energy Steven Chu announced about a year ago that cool roofs (like those installed by Conklin contractors) would be mandatory on all Department of Energy (DOE) facilities. He also urged other federal agencies to follow suit. Chu, also a Nobel-prize winning scientist, stated a potential 10-15% reduction in energy use for those buildings (depending on the configuration of the building and other variables) "simply by having a white roof."

Energy savings aren't the only benefit of cool roofs. The two other reasons Chu mentioned for his advocacy of cool roofs are the role they play in helping mitigating global warming, and their ability to reduce urban heat islands.

Urban heat islands are a result of dark roofs and asphalt pavements in concentrated urban areas increasing the ambient air temperature between 6 and 8 degrees compared to suburban or rural areas. An average 50-65% of urban surfaces are covered with roofs or pavement, and Chu cited a Lawrence Berkeley National Laboratory (LBNL) study that says increasing the reflectance of those surfaces would have the same effect in terms of global warming mitigation as removing every car in the world from the road for 11 years.

Further quantifying the benefits of cool roofing will be the goal of a multi-year long DOE initiative. The Cool Roofs Roadmap lays out research into the exact impact of cool roofing on three levels:

1. Trimming building energy use
2. Mitigating the urban heat island effect
3. Reducing global warming

The Cool Roofs Roadmap, currently in draft version 2.0, is expected to be finalized by the end of this fiscal year according to Marc LaFrance, building envelope program manager at DOE. The roadmap builds on current and past research to provide proof, and therefore act as a basis for policy, of cool roof benefits.

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Cool Roofs are Good for the Environment

Energy savings are not the only reason to opt for a cool roof like those offered by Conklin. Researchers who pioneered the technology in the 1970's were motivated primarily not by the cost savings that cool roofs bring for building owners, but by the significant environmental benefits they offer for cities that widely use them.

Art Rosenfeld (Commissioner of the California Energy Commission) pioneered the study of urban heat islands — a phenomenon in which the air temperature in and around urban areas is raised by 6 to 8 degrees Fahrenheit primarily as a result of the prevalence of heat-retaining surfaces like dark roofs and asphalt streets. Because of their high emissivity and their ability to maintain low surface temperature, cool roofs have a well-documented ability to combat the urban heat island effect.

Urban heat islands are associated with increased pollution and cooling costs, negative health effects, and even decreased workplace productivity because of the impact of poor air quality. “Ozone — call it smog — is extremely temperature dependent,” says Rosenfeld. “In Los Angeles, when the average daily temperature is 72 or below, there is ozone in the air but there are no smog episodes. When it goes up to 92 degrees, you have 100 percent likelihood of smog episodes. When you have an urban heat island, you are artificially increasing that temperature through manmade means, and the negative results for the environment and for public health are significant.”

While the urban heat island effect is most severe in warm climates, it is not just building owners in Los Angeles, Phoenix, Las Vegas, Albuquerque, Houston, and Dallas who should be concerned about it.

“Cities in the north as well as in the south of the country are affected by this phenomenon,” says Rosenfeld. “Believe it or not, the city of Toronto is an urban heat island.”

The environmental benefits of cool roofs are prompting municipal and state agencies across the nation to consider mandating their use as a matter of policy. California blazed the trail of incorporating cool roofs into building code. Following a 1999 analysis that revealed the potential energy savings afforded by cool roofs, Title 24 introduced credits for facilities that opted for cool roofs. Starting in October 2005, California began requiring the use of cool roofs in certain applications. Cities as far north as Chicago have since followed suit.

To learn more about the environmental and other benefits of cool roofing, ask a professional roofing contractor in your area who is an expert in cool roofing.

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Cool Roofing Not Specific to a Single System

Ask any expert to define "cool roof", and his or her explanation will likely include the words “reflectivity” and “emissivity.”

What is a Cool Roof?

Any roof that can boast strong performance in those two areas (the ability to reflect sunlight off a facility’s rooftop while minimizing roof temperature) is a good candidate for the designation of "cool roof".

A cool roof is any roofing system that can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the building) and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy), helping to improve the energy efficiency of the building and mitigating the urban heat island effect.  Most cool roofs are white or other light colors.

The term cool roof can also refer to a geo engineering technique to address global warming through solar radiation management, provided that the materials used not only reflect solar energy, but also emit infra-red radiation (thereby cooling the planet).

Cool Roof Options

The sky is the limit when it comes to choices of systems that qualify as a cool roof - the idea that opting for a "cool roof" limits you to a specific type of product is a common misunderstanding. You can get a cool roof in almost any material you might be considering. For example, Conklin offers cool roofing solutions for fabric reinforced, metal, foam, EPDM, and single-ply systems.

For more information on cool roofing options, please contact a professional roofing contractor in your area that specializes in cool roofing.

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Staying Cool with Cool Roofs

Performance of a cool roof can be adversely affected by accumulated dust or debris, which may reduce the material's reflectivity by as much as 20%. For some applications, ongoing cleaning and preventative maintenance is something every building owner and property or facility manager should consider, so you may want to think twice about putting a reflective roof system on a building where you are going to have a lot of dust and debris if you are not going to institute a regular cleaning schedule.

Aesthetics is another factor to be weighed when considering a white reflective roof system. The color of the roof can be part of the architecture, so that is an important consideration for some people being that cool roofs are typically light in color.

Although the color options available are quickly expanding, as researchers find ways to increase the reflective properties of colored materials. There are many more options for cool roofs today than there were even five years ago. Because of all of the benefits of cool roofing, this is an ever-evolving field.

With today’s cool roofs available in a wide range of types and from a variety of manufacturers like Conklin, making the best choice for a home or building can be a challenge since there is no simple way to determine which roof system is the "best". Efficiency ratings are a key indicator, but this is a tricky issue because when you talk about a roof you’re really talking about a number of different components that may have different efficiency characteristics. The best option is to discuss roofing options with a roof consultant or professional roofing contractor who is knowledgeable about cool roofs.

While the considerations may seem endless, when it comes to cool roofs there are very few drawbacks. In most cases there is little to be lost as a result of choosing a cool roof. If you can arrive at the right combination of insulation and reflectivity, a cool roof is usually a no-brainer.

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Cool Roofs are Affordable and Long-Lasting

The initial cost of a cool roof varies with the type of product specified. For a membrane that is naturally light-colored such as TPO or PVC, there would be no additional cost. But if a membrane is added to make a dark-colored roof reflective, the cost would be higher because it would need to be coated with a reflective roof coating like the ones from Conklin. You may also be eligible to take advantage of one of the rebate or incentive programs that are in place in some areas to encourage the use of cool roofs.

There is a lot of support from utility companies for the increased use of cool roofs, because they are an effective way to decrease peak demand. Offering incentives is a lot cheaper for the utility companies than building a new plant to accommodate everyone’s peak usage.

Emerging evidence points to the possibility that cool roofs actually last longer than standard roofs. Because a cool roof doesn’t heat up as much, it doesn’t go through as much expansion and contraction, which means less wear and tear. RoofPal has data to support the existance of thermal shock, which is caused by rapid and ranging temperatures of the roof surface. Cool roofs do not experience nearly as much thermal shock, which could lead to a 20 percent longer roof life - another savings benefit.

If a roof is well insulated, the effect of a cool roof on energy consumption is reduced because heat from the roof does not penetrate the facility as easily. Insulation does not affect thermal shock or roof life though. There is a “winter penalty” that results when a cool roof reflects solar heat that could reduce heating costs by warming a home or building during winter months, but experts say this penalty is small — perhaps a difference of only about 5 percent.

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