Cool roofs are roofs consisting of materials that very effectively reflect the sun's energy from the roof surface. Cool materials for low-slope roofs are mainly bright white in color, although non-white colors are starting to become available for sloped roof applications.

Cool Roofs must also have high emissivity, allowing them to emit infrared energy. Unfortunately bare metals and metallic coatings tend to have low emissivity and are not considered cool materials.

Cool roofs reduce the roof surface temperature by up to 100oF, thereby reducing the heat transferred into the building below. This helps to reduce energy costs, improve occupant comfort, cut maintenance costs, increase the life cycle of the roof, and reduce urban heat islands along with associated smog.

How can I benefit from a Cool Roof?

Some benefits of Cool Roofs include:

• Save on annual electricity bills by reducing summer air conditioning costs.

• Save peak electricity demand costs if you have time-of-use metering.

• Reduce roof maintenance and replacement expenses by extending roof life.

• Increase indoor comfort in summer by reflecting heat from the roof surface.

• Reduce the heat island effect in cities and suburbs.

• Reduce air pollution and smog formation.

• Reduce roofing waste added to landfills

Did you know? 7-10% of U.S. landfills are comprised of roofing waste.

Case Study: Nationwide® Scottsdale Insurance Company

In the beginning of August 2009, we installed HOBO data loggers (Onset Computer Corporation) on the roof of Nationwide® Scottsdale Insurance Company headquarters in Scottsdale, Arizona, as well as on the roof of a similar building next door in the same corporate plaza.

We collected temperature readings on the roof surface and directly beneath (specifically, the temperature of the bottom of the roof deck, which is the ceiling of a low-traffic, non-air conditioned stairwell) once per hour for a month on both buildings to measure the roof surface temperature differences, as well as the energy efficiency difference between the original roof system (a ballasted EPDM over 4” of insulation on a concrete roof deck with 2” of river rock blanketing the rooftop) and the new roof system (Polyglass Poly ISO board insulation under a self-adhesive Polyglass Elastoflex SA membrane and a PolyKool cap sheet).

Download the Starkweather Roofing Cool Roof Case Study

Read the Western Roofing Magazine article about this project

If you have any questions about this study, please email us.

If you would to read the summary version of the case study instead, please click here.

· If you would like to review the data and Professor Richard Bird’s analysis, please click here.

The bottom line? Even with a 6” concrete roof deck (not typical in Arizona) and a roof surface material with a solar reflective index (SRI) value of only 84, Nationwide® still decreased their monthly energy consumption by 7.8%. If the building had a plywood roof deck (very typical in Arizona) and/or had a high quality roof coating with an SRI value of 100 or greater, the energy efficiency of the building would be 2-3 times greater. Starkweather Roofing is conducting another analysis using these conditions and will post the results to this page in October 2009.

An article based on this cool roof case study is scheduled to be featured in the June 2010 edition of Professional Roofing ECO magazine.

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The Future of Cool Roofing?

A team of recent MIT graduates have developed roof tiles that change color based on outside temperature, and are now working on creating a commercially-viable roof coating that does the same thing. Read our article on this exciting new development.

Here are pictures demonstrating the process to install the HOBO data loggers

NationwideGainey - Data Loggers 02.JPG

Placing the data logger sensor on the

Scottsdale Insurance Company roof.

NationwideGainey - Data Loggers 03.JPG

Securing the sensor to the roof with a

piece of PolyKool cap sheet.

NationwideGainey - Data Loggers 11.JPG

Placing the data logger sensor on the building

next to the Scottsdale Insurance Company building.

NationwideGainey - Data Loggers 12.JPG

Sensor is placed directly to the

ballasted EPDM roof membrane.

NationwideGainey - Data Loggers 14.JPG

Securing the sensor to the roof with a

ballasted EPDM roof membrane.

NationwideGainey - Data Loggers 15.JPG

Secured sensor is recovered with 2” of river rock

NationwideGainey - Data Loggers 20.JPG

Sensor secured to the underside of the

roof deck in a non-air conditioned stairwell

Starkweather Roofing, Inc.

28248 North Tatum Boulevard, Suite B-1 PMB 612 | Cave Creek, Arizona 85331

Phone: (602) 997-0529 or Toll-Free (888) 997-0529 | Fax: (602) 395-0369 or Toll-Free (888) 995-0369 | Email: Starkweather@StarkweatherRoof.com

Arizona Commercial License R.O.C. # 120218 | Arizona Residential License R.O.C. # 120219 | New Mexico License # 363970