Page 20 - Green Builder Magazine Nov-Dec 2017 Issue

the capacity of cool roofs to relieve
the urban heat island effect is more
pronounced during heat waves,
when heat islands are particularly
intense, sometimes deadly.
The growth of cities continues, so
making them cleaner, more livable
and better for well-being is essential.
Where green roofs struggle with
the high costs and special skills
needed for implementation, cool
roofs are cheaper, simpler and more
like conventional installs. They are
eminently doable. Though regular
cleaning is needed to sustain top-
notch reflection, maintenance needs
are much lower as well. Despite
this ease, it is necessary to consider
context. Cool roofs can create glare
for their neighbors, and their impact
depends on local climate. Hotter
places benefit more from their
cooling effect, while suffering less
CREDIT: GRAMICIDIN/FLICKR in cold months. In colder climates,
from their reduced heat retention
the insulation of green roofs may be
more optimal year-round.
Cool roofs are not a new concept,
Singapore special. Nanyang Technological University’s School of Art, Design and Media features a but have been slow to take root
five-story green roof sloped at a 45-degree angle. The roof doubles as a scenic outdoor communal worldwide. They are on the rise in
space and keeps the building’s ambient temperature low.
the United States and European
In October 2016, San Francisco became the first U.S. city to adopt Union, while getting increasing attention, and occasionally official
a green roof mandate. As of this year, 15 percent to 30 percent of commitment, elsewhere. California has been their greatest champion,
roof space on new buildings must be green, use solar power or both. integrating cool roofs into the state’s building efficiency standards, Title
Other cities should follow suit. 24, a decade ago. The success there shows the way forward, including
the importance of regulations, rebates and incentive programs.
A Perfect Patchwork The evolution of cool roof technology is also promising. Traditional
By attending to the life both within buildings and on top of building aesthetics have worked against so-called “white roofs,” but
them, the world’s current patchwork of barren roofs can flower, cool roof materials now come in an array of colors, and adjustable
transforming cities into life-supporting systems. Cool roofs are kith levels of reflection may ultimately address their downside in winter. In
and kin to green roofs, achieving similar impact but doing so with the interest of “bending back” not just solar energy and air temperature
different methods, hurdles and boons. “Reflection” is from the Latin but also emissions, cool roofs hold considerable promise. GB
for “bending back,” and cool roofs do just that. When solar energy Note: This article is taken from Drawdown: The Most Comprehensive Plan
hits a conventional dark roof on a 99-degree day, just 5 percent of it Ever Proposed to Reverse Global Warming, which describes the 100 most
is reflected back into space. The rest remains, heating the building substantive solutions to climate change, as well as their financial histories,
and surrounding air. the carbon impacts they provide, the relative cost and savings and each
A cool roof, on the other hand, reflects up to 80 percent of that solution’s path to adoption.
solar energy back into space. Cool roofs take a variety of forms:
light-colored metal, shingles, tiles, coatings, membranes and more Paul Hawken is an author and executive director of
being developed. climate research coalition Project Drawdown. He is a
Whatever technology is used, in an increasingly urban and keynote speaker at Sustainability Symposium:
warming world, sending solar energy back to where it came from, Champions of Change on Jan. 8 in Orlando, Fla.
rather than absorbing it, is essential. Not only do cool roofs reduce To register, visit www.greenbuildermedia.com/
heat taken on by buildings, driving down energy use for cooling, they champions-of-change-2018.
also reduce the temperature in cities. Recent studies have shown that

18 GREEN BUILDER November/December 2017 www.greenbuildermedia.com

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