http://www.nrdc.org/media/2012/120613.asp
Installing green roofs and cool roofs in
southern California could save consumers more than $211 million in
energy bills and reduce emissions equivalent to removing 91,000 cars
from the road each year, according to a new study from the Natural
Resources Defense Council and the Emmett Center on Climate Change and
the Environment at UCLA School of Law. Installing green roofs will
additionally reduce stormwater runoff that pollutes our beaches.
“Southern California is facing a complex, and mostly worsening, set of sustainability challenges but solutions exist,” said Noah Garrison, project attorney for NRDC’s water program. “Green roofs and cool roofs are a solution that can be implemented today. Taking simple steps like installing drought resistant plants
on a roof surface or painting roofs to reflect the sun’s energy can
dramatically reduce our dependence on fossil fuels and, for green roofs,
reduce the amount of pollution that flows to our rivers and beaches.”
According to the report, “Looking
Up: How Green Roofs and Cool Roofs Can Reduce Energy Use, Address
Climate Change, and Protect Water Resources in Southern California,” if green roofs or cool roofs
were installed on 50 percent of existing roof surfaces for residential,
commercial, and government and public use buildings in southern
California, it could save up to 1.6 million megawatt hours of
electricity annually, enough energy to power more than 127,000 homes in
California and save residents up to $211 million in energy costs each
year based on 2012 rates. The energy savings would cut carbon pollution
by 465,000 metric tons annually.
Because green roofs absorb and evaporate rainfall,
installing green roofs on 50 percent of the existing roof surfaces
could reduce stormwater runoff by more than 36 billion gallons each year
- enough to fill more than 54,000 Olympic-sized swimming pools -
significantly reducing the volume of pollution reaching our local
waters.
“The scale of these benefits is truly impressive, and justifies a much
more aggressive set of policies and incentives to help advance the
adoption of green roofs and cool roofs in our region,” said Cara
Horowitz, the Andrew Sabin Family Foundation executive director of the
Emmett Center on Climate Change and the Environment at UCLA School of
Law. “If Los Angeles and other southern California cities provided
better incentives for residential and commercial building owners to
install green roofs and cool roofs, we would have healthier, more
sustainable neighborhoods and save money too.”
Ensuring new development projects install green and cool roofs can also
provide tremendous savings. Installing green roofs and cool roofs on
50 percent of new construction and redevelopment would save up to one
million megawatt-hours per year by 2035 and $131 million in electricity
costs during that time period, while cutting carbon pollution by 288,000
metric tons annually, which is the equivalent of taking more than
56,000 cars off the road each year. It would also result in a reduction
of 20 billion gallons of stormwater runoff in southern California each
year by 2035, significantly reducing the volume of pollution flowing to
local rivers, lakes, and beaches.
Additionally, green and cool roofs can cut urban temperatures. Cities
create their own heat islands—areas where surface and ambient air
temperatures are higher than in surrounding undeveloped or rural land.
The dark, paved surfaces in urban and suburban areas absorb and radiate
heat back into the surrounding communities. These increased air
temperatures worsen smog and other air pollution, and can result in
increased heat-related illnesses. Installing green roofs and cool roofs
across urban landscapes can help cool down neighborhoods, reducing
temperatures in urban cores by as much as 3.5 degrees Fahrenheit, with
air quality and human health benefits.
“Green roofs and cool roofs make sense for southern California – we
have mild winters but hot summers, and these types of roof can keep
buildings and entire cities cooler, saving energy and protecting water
resources in the process,” said Garrison.
Background
Green roofs have a thin covering of soil and live plants growing on
them which provide shade, insulation, and evaporative cooling that
reduces temperatures on the roof surface and in the building interior
below. The temperature of a green roof can often be cooler than the
surrounding ambient air, resulting in less energy needed to cool the
building interior. Conversely, the temperatures on the surface of a
dark, conventional roof may exceed those of ambient air by 90°F (50°C)
or more on a hot, sunny day, and much of that heat transfers into the
building’s interior, requiring more energy for cooling.
Cool roofs, like green roofs, use smarter materials to reduce energy
demand and lower temperatures compared with traditional rooftops. Cool
roofs use reflective materials, often but not always light-colored, to
reflect more of the sun’s energy than dark, traditional roofs, and to
more efficiently transmit heat from the building’s interior. Compared to
conventional dark roofs, the surface of a cool roof can be 50° to 60°F
(28° to 33°C) cooler on a hot, sunny day.
Natural Resources Defense Council (NRDC) www.NRDC.org
Press Release dated June 13, 2012
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