On a typical summer day most cities in the world are several degrees warmer than the
adjacent countryside. It is known as the heat island effect. Our cities have become
hot and harsh environments and require a vast amount of energy to make life
comfortable. The strain on power lines is enormous, and electric companies must
scramble to meet peak demand. In fact, heat waves kill more Americans than all other
But now there’s a way to make urban centers environmentally friendly and Chicago
has a project going that could help the planet go greener and cooler, and all we have
to do is to look up to the roof tops. Taking it’s queue from Germany, which 10% of
all roof tops have been “greened”, Chicago City Hall now has a green roof. 20,000
sq feet of prairie, 12 stories above street level of downtown Chicago. Green roof
tops like this can be 60 degrees cooler than conventional black tar rooftops.
The air conditioning intake is located directly over the green roof. That makes
it easier to air condition the inside. Which brings the air conditioning costs down
and makes the ambient environment cooler. The prairie garden has saved Chicago
City Hall $6,000 per year in energy costs. Eliminating the need for power plants
to produce 45 tons of CO2 emissions.
It also helps to reduce the amount of storm water that floods into Chicago’s over-
taxed sewer system. The roof has between 2 to 4 inches of super light soil, 80
percent of which is inorganic allowing it to absorb the rain water and hold it for
48 hours during which time the plants use it or it evaporates.
Most black tar roofs need to be replaced every 20 years. But Chicago City Hall’s
green roof may not have to be replaced for 50 years or more. Because the layers
of soil and vegetation, protects the roofs membrane from harmful ultra violet
rays. A movement is underway in Chicago to encourage the greening of rooftops across the city.
If all roofs in a city were “greened”, temps could drop by 12 degrees. Altho the
initial investment is high, the results could ultimately save millions of dollars.
Not to mention, the view flying over Chicago will be much more appealing seeing
green rooftops versus black rooftops emitting shimmering waves of heat.
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