Residential and commercial construction continue to go strong in Maricopa County and throughout Arizona. With that growth we are seeing a push for using more sustainable products made from a variety new “green” materials. Few places on the map cook summer temperatures as hot as we do in Arizona, so it makes sense that “cool roofs” would find their way to the top of a growing number of commercial and residential properties. Builders are increasingly using them to combat urban heat islands and to save on energy use. Arizona has the optimal climate for cool roofs. But while cool roofs may lower utility bills in the short term, research shows they may not be so cool for the environment in the long term.
What is a cool roof?
The U.S. Department of Energy defines cool roofs as roofs that reflect more sunlight and absorb less heat than standard roofs. They achieve this effect by using a light-colored, highly reflective paint on the tiles, shingles or sheet coverings that go on the roof. The impact is dramatic. A standard dark roof will heat up past 150 degrees in the summer, while a cool roof will stay at least 50 degrees cooler.
What are the benefits of a cool roof?
In addition to lowering the temperature of the roof itself the benefits of a cool roof include:
- Reduces air conditioning use.
- Improves indoor comfort for non-air-conditioned spaces such as covered patios
- Combats the heat island effect and helps cool neighborhood.
- Lowers peak electricity demand and helps avoid outages.
Where do cool roofs work best?
Cool roofs are best for residential and commercial construction in hot, dry climates with mild winters. Phoenix and Tucson fit the bill perfectly. In areas with very cold winters, a cool roof can translate into a higher heating bill. The cool roof of summer also means a much cooler roof in cold weather too. Any gains made in summer energy savings can evaporate in winter if you have to crank up the heat more than you normally would.
Wait, cool roofs can make it hotter?
If Arizona is the perfect place for cool roofs, then why not push to replace every roof? Climate researchers say, not so fast. In fact, a couple of studies suggest this is not a good idea. The authors of a 2011 Stanford University study, poses that reflected heat from cool roofs could re-heat brown and black soot particles in the air and actually increase local temperatures, rather than lower them.
Arizona State University did a study as well, in 2014, that presented equally disconcerting conclusions. If all roofs in an urban city were replaced with cool roofs, researchers believe the deflected heat and sunlight back into the atmosphere would actually cause a multitude of impacts on our weather system. The result would be thinner clouds and less rain. Imagine monsoons rolling over the state and never dropping rain.
An alternative to cool roofing may be simply increasing the amount of vegetation and trees planted. Researchers say adding true greens rather than just green building materials can replace some of the natural vegetation lost during construction and provide natural shade.
Cooling the urban heat island
Phoenix’s extensive urbanization has led to an urban heat island that increases steadily at a rate of almost one degree every ten years. The city studied the impact of cool roofs, tree shade and various landscaping models on this urban heat island. While cool roofing did show a temperature reduction, the greatest cooling came from shade trees, vegetation and grassy yards. In fact, bumping the number of shade trees by 25 percent showed the largest cooling effect.
Plant trees
The use of cool roofing is expected to grow at a healthy rate not just in the US, but around the world. It fits in with a move toward building sustainable buildings with “green” materials. However, cool roofs represent a mixed bag in terms of cooling our urban heat islands. The lower energy bills may exact too great a price from our environment, however shade trees and rethinking the landscaping in both commercial and residential neighborhoods may offer us a truly green alternative.
At Landmark Title, our residential and commercial teams have extensive experience assisting clients with their real estate transactions. To use Landmark Title’s residential title and escrow services contact us at (602) 748-2800.