Unappreciated Advantages of Green Roofs

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While a cityscape’s concrete slabs and dirty sheet metal blanket what was once vegetative abundance, green roofs inspire nature to strike back. Nestled across the urban and suburban skyline, green roofs provide a real opportunity for production as well as a host of environmental benefits. Despite this, green roofs remain less appreciated than they should be. Let’s look at the:

  • Benefits of green roofs
  • Types of green roofs
  • Largest green roof in the United States
  • Green roof cost estimates

Green Roof Design

With a big mention on the new season of the podcast Start Up, the green roof at the Ford factory clocks in as the largest in the United States. Since it’s completion 13 years ago, all original plant species have survived, largely on rainwater, and after over a decade of operation no replacements have been necessary. The roof is made from drought resistant sedum, spanning 10.4 acres (about 8 football fields) and sustaining a dynamic ecosystem of over 35 insect, spider, and bird species and 11 plant species.

ford factory green roof

Ford Factory Green Roof

Compared to a normal roof, this design offers a number of benefits for the facility (from their site):

  • Cleaner Storm Water: The Living Roof’s primary function is to collect and filter rainfall as part of a natural storm water management system. Working together, the Living Roof, porous pavement, underground storage basins, natural treatment wetlands and vegetated swales significantly reduce the amount of storm water flowing into the Rouge River, while also improving water quality.
  • Cooler Surroundings: Planted with sedum—a drought-resistant perennial groundcover also known as stonecrop—the Living Roof helps reduce the urban “heat effect” created by acres of tarred and paved surfaces. It also insulates the building, reducing heating and cooling costs by up to five percent. The sedum traps airborne dust and dirt, absorbs carbon dioxide, and creates oxygen, all of which help improve air quality. The living roof also creates a habitat for birds, butterflies and insects.
  • Longer Roof Life: By protecting the underlying roof structure from ultraviolet radiation and the thermal shock (expansion and contraction) caused by warm days and cool nights, the Living Roof is expected to last at least twice as long as a conventional roof. This could save millions of dollars in roof replacement costs.

And these ideas are catching on in areas where storm water remediation is a top priority like this proposed site for a new FBI headquarters along the Anacostia River.

Types of Green Roofs

Besides their inherent aesthetic appeal, green roofs have real advantages. There are two main types of green roofs: extensive and intensive.

Extensive green roofs are characterized by a shallow soil depth and are usually populated by species like sedums, small grasses, herbs, or flowering herbaceous plants, with little needed maintenance and no permanent irrigation. Extensive green roofs are also often cheaper than intensive green roofs, running between$50-100/square foot. The Ford factory roof above is an example of an extensive green roof.

Intensive green roofs are designed for vegetative production. These could include roofs covered in planters, roofs with deeper soil depths than extensive roofs, or greenhouse roofs (though some in the industry may argue on that point). These require more maintanance in water but offer more options of species for cultivation. They are also more expensive, running upwards of $90/square foot. Below are examples of intensive green roofs. system. http://www.urbanharveststl.org/food-roof-farm/ [awesome video]


Gotham Greens Green House Greenpoint

Gotham Greens in Greenpoint


Brooklyn Grange: check out this article where the photo came from that showcases some other very cool rooftop farms

Not only are these farms environmentally friendly and visually inspiring (a relief from the industrial greys of a city), but they can nourish the community and local food scene as well. There are more green roofs now than ever before (go figure), and they are only gaining in popularity. With the host of benefits they provide, it’s no wonder why.

What do you think is the most useful rooftop application? Leave your comments below. And if you liked this article, you would probably enjoy this one about green walls as well.

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