WHI T E is the Greenest Color
Although white walls are widely accepted to
be aesthetically pleasing, they are not used
as much as they should be.
reflect much of the sun’s energy back into space,
while a black roof absorbs most of the sunlight
and turns it into heat. A black roof can get more
than 60°F ( 33°C) hotter than a white roof, sig-
nificantly heating both the building and the out-
door air. As a result, buildings get heated twice
by their black roofs — once directly through
the roofs, and secondly by the increased air tem-
perature of the neighborhood. Cities can be as
much as 16°F ( 9°C) warmer than the surround-
ing rural areas due to the extra absorption of
dark roofs and pavements and the lack of trees.
This “heat island effect” also increases pollution
levels in cities.
White buildings can also reduce the energy
required for lighting a building. White ceilings
and interior walls make electric lighting more
efficient, and white roofs and exterior walls can
make daylighting more efficient in urban areas.
Because daylight enters windows from the sky,
most of the light ends up illuminating only the
indoor spaces near the windows. On the other
hand, much of the light reflected from white
walls and the roofs of lower buildings enters
windows from below, thereby illuminating the
the largest and most cost-effective opportunities we have to counter
global warming, improve health and strengthen security.”
— U.S. SeCre TAry OF eNerGy STeVeN CHU
48 July/August 2012 SOLAR TODAY solartoday.org
When it comes to solar-responsive design, perhaps the lowest- hanging fruit is choosing white. Selecting white design elements can save much energy, thereby
saving money and helping to save the planet.
White roofs dramatically reduce overheating
in both buildings and cities. A white roof will