Green Roofing 101

by Rana WaxmanFebruary 6, 2019

Driven by the enthusiasm for sustainable design, green roofs (and green walls) are growing in popularity. Also called “living architecture” by Green Roofs for Healthy Cities (GRHC), the structures are both pretty and practical.

There’s an indication that the first green roofs—the Hanging Gardens of Babylon—were around in 500 BC, so it’s not a fading trend. That said, there’s a proper way to build a green roof so don’t try to simulate the experience with potted plants. Rather, think of them as a form of design that is becoming more popular as cities who want to be eco-friendly look for ways to conserve energy and protect the environment.

Green Roof

What is a Green Roof?

A green roof is an engineered roof with a purpose. You may also see buildings where a patio or ledge converts to get the same results as a roof, but this is usually for large edifices.

Mostly, green areas are permanent and pre-planned extensions of the roof itself. There are two ways to build them: (1) modular or (2) using component-based systems. Either way, they aren’t designed to grow trees with long roots but instead use specific types of greenery (like sedum plants). They also have a waterproof base and per the GRHC, include some other features such as:

  • Root repellant system
  • Drainage system
  • Filter cloth
  • A lightweight growing medium
  • Vegetation – there may be mandates about the type

Importantly, green roof development involves a “contained” green space which means that the entire roof may contain other installations like a walkway or paved surface. The latter will depend on the type of building (residential or commercial) and the amount of space set aside for the green roof. Since water-saturated soil can be heavy, each roof structure must also be engineered to bear the load.

The Many Uses of Green Roofs

Centuries past the Babylonians, the Europeans used green roofs to keep their home cool in summer and insulated in winter. These are practices which are still in effect today, though in more sophisticated ways.

For instance, a green roof can boost energy efficiency and filter pollution. For communities, they can lower the temperature in cement-laden cities (Urban Heat Island Effect) and absorb rainwater. As a result, green roofs may improve a city’s overall stormwater drainage and thus help to improve its resiliency to flooding. For this reason, the laws governing green roofs may fall under the purview of a city’s water department.

The Advantages of Having a Green Roof

The pleasing aesthetics of green roofs are one of many benefits. In any space, they can serve as a heavenly oasis which may amp up the value of any property. Apart from the lovely optics, green roof technology can benefit private homeowners by:

  • Serving as a fire retardant
  • Reducing the usage of heating, ventilation, and HVAC systems
  • Diminishing noise from outside
  • Bringing a tax abatement, green roof rebate, discount on water utility fees, etc.
  • Insulating a home

How are Green Roofs Energy Efficient?

Studies show that green roofs are energy efficient. When it rains, the rooftop plants slow the flow and remove CO2 and pollutants from the drain water. Also, green roofs reflect solar radiation (unlike black roofs) and thus help keep temperatures low even inside. If you’ve ever worn a black t-shirt in the middle of summer, you know that the darker color is like a magnet for heat, whereas lighter colors seem to keep you cooler. It’s similar with green roofs.

The Getty Center

10 Cities that Top the Charts for Green Roofs

The GRHC’s Annual Green Roof Industry Survey ranked North American cities with the greatest square footage of green roof installations. The top were:

  1. Washington, DC
  2. Newark, NJ
  3. New York City, NY
  4. Seattle, WA
  5. Portland, OR
  6. Toronto, ON (Canada)
  7. Philadelphia, PA
  8. Chicago, IL
  9. Culpeper, VA
  10. Gaithersburg, MD

As more cities (like Denver) mandate green roofs, look for others to join the list.

Exciting Roof Tops for Your Bucket List

If you intend to build a home with a green roof, you’ll need to start with a sound architectural plan that aligns with your city’s building codes. But that doesn’t stop you from gaining inspiration from the nation’s many well-manicured green roofs. Here are a few to visit!

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About The Author
Rana Waxman
Rana Waxman parlays years of work experience in several fields into web content creation aligned with client needs. Rana's versatile voice is supported by a zest for research, a passion for photography, and desire to provide clients with a purposeful presence online. In her non-writing hours, Rana is a happy yogini, constant walker, avid reader, and sometimes swimmer.