Greenroof Benefits
© Roofscapes, Inc.

Benefits

Vegetated roof covers add value by:

  • Extending the service life of roofs,
  • Reducing energy costs,
  • Conserving valuable commercial space that would otherwise be required to provide stormwater runoff controls, and
  • Increasing property values.

The multiple layers protect the underlying roof materials from the elements by:

Protecting from mechanical damage (mostly from humans, but also from wind blown dust and debris, and animals),

Shielding from ultraviolet radiation, and

Buffering temperature extremes, minimizing damage from the daily expansion & contraction of the roof materials.

 

Mature growth at the Fencing Academy of Philadelphia.

© Roofscapes, Inc.

Temperature data from the Roofmeadow®

installed at the Fencing Academy of Philadelphia.

What about weight?

Vegetated roof covers can be readily engineered to conform to the load requirements of most roofs. Beautiful vegetated roof covers weighing 15 pounds per square foot have been installed. This weight is comparable to the weight of gravel ballast placed on many conventional roofs.

Where heavier loads can be supported, dramatic landscaping accents can be incorporated, including garden walks, flowering shrubs, and rock gardens.

Vegetated roof covers furnish many of the amenities of open space, by:

  • Moderating the temperature on and surrounding the roof
  • Filtering dust from the air
  • Absorbing rainfall
  • Insulating the host building from the elements
What about moisture?

Control of stormwater runoff is achieved by mimicking the processes that occur in nature, intercepting and delaying rainfall runoff by:

    • Capturing and holding precipitation in the plant foliage,
    • Absorbing water in the root zone,
    • Slowing the velocity of direct runoff as it infiltrates through the layers of vegetated cover.

For small rainfall events, little runoff will occur and most of the precipitation will eventually return to the atmosphere by evaporation and transpiration. For larger storms, vegetated roof covers can significantly delay and attenuate the discharge of runoff from roofs.

Compared to many other stormwater management practices, vegetated roof covers are unobtrusive, low maintenance, and reliable management systems. Vegetated roof covers are particularly effective when applied to extensive roofs, such as those that typify commercial and institutional buildings. They can be designed to achieve specified levels of stormwater runoff control, including reductions in:
  • Total annual runoff volume (reductions of 50 to 60 percent are common place for vegetated roof covers), and
  • Peak runoff rates for selected design storm events
Stormwater runoff for a 3.35-inch, 24-hour rainfall event. This Roofmeadow incorporated a 3-inch deep layer of growth media.
© Roofscapes, Inc.

Vegetated roof covers may offer the only practical "at-source" technique for controlling runoff in areas that already are highly urbanized. Due to their potential for addressing flooding impacts in our cities, vegetated roof covers have been featured in many recent stormwater management handbooks.

For German case studies in which green roofs are an inegral part of urban stormwater control, see

Study of Extensive “Green Roofs” in Berlin, by Manfred Köhler and Marco Schmidt and Production and Transportation Center Bondorf, Germany.

 

 

 

 

Want to know more?

Consult Green Roof FAQs.