![](benefits1.jpg) |
©
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.
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
![](benefits6.jpg) |
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.
|