EarthTalk: I’ve heard that simply painting
your roof white can reduce household electricity bills by
40 percent. Is this something any of us can do?
—Susan Pierson, Sumter, SC
90 percent of U.S. buildings have dark-colored roofs
which, when exposed to full sun can increase in
temperature by as much as 90 °F. A white roof
typically increases temperatures only 10-25 °F
above ambient air temperatures during the day. Pictured:
The White Roof Project at work.
© White Roof Project
anyone can do it—and the benefits can be significant,
especially for those in warmer climates who expend a lot
of energy keeping cool. But most of the world’s roofs,
including on some 90 percent of buildings in the U.S., are
colored roofs absorb more heat from the sun’s rays
than light colored ones, and as such get much hotter. A
black roof exposed to full sun can increase in temperature
by as much as 90 °F (50 °C), meaning the air conditioning
inside has to work that much harder to compensate for the
added heat load.
a white or reflective roof typically increases temperatures
only 10-25 °F (5–14 °C) above ambient air
temperatures during the day. This translates into a savings
of up to 15 percent on air conditioning energy use over
a year for a typical one-story residence, according to the
U.S. Department of Energy (DOE). The upshot of this energy
savings is not only cost savings for the consumer—annual
energy bill savings of 20-40 percent aren’t uncommon
for single story homes in America’s Sun Belt—but
also reduced air pollution and greenhouse gas emissions
generated in the production of electricity.
white roof also helps keep buildings and houses without
air conditioning cooler in the summer than they would otherwise
be. And it also helps mitigate the “urban heat island
effect” whereby a city can be 6-8 °F warmer than
its surrounding areas on warm summer days.
non-profit White Roof Project promotes the concept across
the U.S. and last year painted some 30 buildings, helping
hundreds of families lower their energy bills in the process.
white roof project is low cost, easy to implement, relieves
stress on the power grid, cuts down on smog, and creates
tangible change for individuals, our communities, and even
globally,” reports the group, which is looking to
expand its work across the country significantly in 2013
and expand internationally in 2014.
White Roof Projects gives away instructions (via a free
downloadable “DIY Packet”) to help do-it-yourselfers
paint their own roofs white without hiring a painter or
roofer. All it takes is a few painting supplies, a couple
of cans of highly reflective elastomeric white paint, and
a plan for how to cover all relevant surfaces properly and
safely. Those who would rather hire someone to do the ladder
climbing and paint application can hire any local painter
green roofs may be preferable from a strictly environmental
perspective in that they contain plants that filter pollutants
and reduce run-off, white roofs may indeed provide more
overall environmental benefit for the cost of a couple of
cans of special white paint. Indeed, painting the roof white
might be the best energy efficiency improvement you can
make to your building or house.
Roof Project; DOE
Cool Roof Fact Sheet.
NEW SET OF ANSWERS IS FEATURED EACH WEEK!
EarthTalk: Why is it that airplane exhaust
is so much worse for the environment than engine emissions
on the ground?
—Winona Sharpe, New York, NY
Intergovernmental Panel on Climate Change reports
that CO2 emitted by jets can survive in the atmosphere
for upwards of 100 years, and that its combination
with other gas and particulate emissions could have
double or four times the warming effect as CO2 emissions
© Hemera Collection
While air travel
today accounts for just three percent of worldwide greenhouse
gas emissions, the carbon dioxide (CO2) and other pollutants
that come out of jet exhaust contribute disproportionately
to increasing surface temperatures below because the warming
effect is amplified in the upper atmosphere.
Panel on Climate Change (IPCC), a scientific intergovernmental
body set up by the United Nations (UN) to provide comprehensive
scientific assessments of the risk of human-induced climate
change, reports that CO2 emitted by jets can survive in
the atmosphere for upwards of 100 years, and that its combination
with other gas and particulate emissions could have double
or four times the warming effect as CO2 emissions alone.
Modern jet engines
are not that different from automobile engines—both
involve internal combustion and burn fossil fuels. But instead
of gasoline or diesel, jet fuel is primarily kerosene, a
common home heating fuel used around the world. Just like
car engines, jets emit CO2, nitrogen oxides, sulfur oxides
contributions to global warming, airplane emissions can
also lead to the formation of acid rain and smog, as well
as visibility impairment and crop damage down on the ground.
The U.S. Environmental Protection Agency (EPA) reports that
aircraft engines contribute about one percent of total U.S.
mobile source nitrogen oxide emissions and up to four percent
around airports in some areas.
environmentalists is the fact that the number of airline
flights is on the rise and is expected to skyrocket by mid-century,
meaning that if we don’t get a handle on airplane
emissions, our other carbon footprint reduction efforts
could be for naught. The U.S. Federal Aviation Administration
(FAA) reports that commercial flights grew nine percent
from 2002 to 2010 and will rise another 34 percent by 2020.
standards are based on guidelines established under the
U.S. Clean Air Act and are set by the International Civil
Aviation Organization (ICAO). Current standards were created
in 1996 and updated in 2006, but environmental leaders want
even stricter limits on greenhouse gas and other emissions.
The IPCC recommends
funding more research into aviation’s effects on climate
to guide the development of aircraft and engine technology,
promoting more efficient air traffic operations and expanding
the use of regulatory and economic measures to encourage
In regard to
economic measures, the European Union (EU) is leading the
way with new rules that assess fees on foreign airlines
based on their CO2 emissions. The new system, which would
require airlines using an airport in Europe to trade for
or purchase permits corresponding to the amount of greenhouse
gases they emit, was supposed to go into effect in 2013
but has been postponed due to intense opposition from foreign
governments which consider it a barrier to trade. EU officials
have threatened to put the plan into effect nonetheless
if airlines or their governments can’t agree on new
stricter emissions limitations.