System Operator

Cool Roofs: Your Questions Answered

Last month Secretary Chu announced that the Department of Energy had installed a “cool roof” atop the west building of our Washington, DC headquarters. The announcement elicited a fair number of questions from his Facebook fans, so we decided to reach out to the people behind the project for their insight on the specific benefits of switching to a cool roof, and the process that went into making that choice.

Jim Bullis (Facebook): So what is the percentage saving of energy bills for this building?

Answer: The West Building cool roof is estimated to save about $2,000 per year in reduced energy costs. In the spring, we will also be installing a cool roof on the Headquarters’ South Building, which will save an additional $6,000 per year. While this represents just a small portion of the total annual energy costs for the building, it is important to note that this cool roof was a no cost initiative, meaning that the West Building roof was already due to be replaced and opting to switch to a cool roof added no additional cost to the project. As a result, these small savings offer an immediate payback.

Kim Greenfield (Facebook): Why aren’t these solar panels instead?

Answer: The roof of our North Building already hosts a 205 kW photovoltaic solar array,which was installed in September 2008. At the time, it was the largest PV array in Washington DC and it generates over 230,000 kWh of electricity per year. We decided to install a Cool Roof on the West building since it would showcase a different type of technology at no additional cost and save money on lower energy bills for taxpayers.

Rakesh Kamal (Facebook): Why cant they just paint it white, instead of installing all those sheets?

Answer: The roof design and construction was awarded through a competitive solicitation. The General Service Administration, which was in charge of the selection process, considered many factors in their decision to award the contract, including cost, durability, and recycling of existing roofing materials. Ultimately they found that while cool roof coatings are available for low-sloped roofs, they would not be best option in this case.

Pwwora (YouTube): Wouldn’t it have been much smarter to use a foam roof with white elastomeric coating?

Answer: Spray foam roofs would have been another option. However, these roofs are really not frequently used on buildings where there is quite a bit of roof traffic because they are not meant to support this abuse.

Be sure to check out the ongoing discussion about cool roofs on Facebook and Twitter, and if you haven’t already, watch Secretary Chu explain how he hopes the Department can set an example for the rest of the nation.

John Schueler, New media Specialist with the Office of Public Affairs, blog.energy.gov