Up on the Roof

This week's newspaper column:

Green roofs are the latest thing in sustainable building technology.

Well, not quite.

Planted roofs were around as long ago as the seventh century B.C. when King Nebuchadnezzar adorned roofs with vegetation in what famously became known as the Hanging Gardens of Babylon.

In Scandinavia and Iceland, people have utilized sod roofs to insulate homes from the extreme cold for centuries.

Fast forward to the twenty-first century and green - or “living” roofs - are making a big comeback.

Cities like Chicago and Portland, Oregon are aggressively encouraging the installation of green roofs on as many rooftops as possible. Ford Motor Company’s River Rouge manufacturing plant sports a 10 acre living roof, and you’ll even find a green roof on the Pentagon.

Why?

Green roofs offer a plethora of environmental, economic, and aesthetic benefits.

While conventional roofs bake in the summer sun hiking surface temperatures to well over 100 degrees Fahrenheit, a planted roof remains roughly the same temperature as you would find under a nice shady oak tree. Extreme heat and ultraviolet rays degrade roofing materials, but a roof protected by vegetation typically lasts two or three times as long, and the insulating characteristics of a green roof keep the inside of a building cooler in the summer and warmer in the winter saving energy year-round.

Municipal officials always complain about the ever-increasing costs of storm water drainage systems. Water falling on hard surfaces (such as concrete, asphalt and roofing) rushes into underground drainpipes that must be sized for maximum capacity. Collectively, green roofs (along with planted areas on the ground) relieve the system of that extreme sudden surge of water runoff minimizing the need for costly expansions of underground piping.

Urban spaces act as “heat islands” and are typically several degrees hotter than the surrounding countryside. Planted roofs lower the ambient temperature of the surrounding area while simultaneously improving the air quality as they absorb carbon dioxide and emit oxygen.

And green roofs have aesthetic qualities too, as vegetation softens the hard edge of the built environment. As living roofs grow more popular, they’ve even been utilized as private patio gardens and as bonus public recreational space.

The cost?

Green roofs can be installed for as little as $10 per square foot and can easily be accommodated on new construction. If added to an existing building, it might be necessary to beef up the structure as planted roofs add at least 25 pounds per square foot to the roof load when saturated.

Want more information? Go to www.greenroofs.com or just type in “green roof” on your computer’s browser and you’ll find a wide variety of interesting planted roofs and resources.

Think about a green roof next time you’re planning a building project; the idea is old, but the benefits are timeless.

Update: A link from Robert to an article about a very cool Richard Neutra house with a green roof:

http://www.treehugger.com/files/2009/03/nothing-new-about-green-roofs.php