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Within a short period of time the entire rooftop is covered with a solid
layer of dense vegetation forming an ecologically friendly environment where
a potentially harmful one existed. The new roof will perform its intended
design functions in an excellent manner, as well as, deliver a multitude
of additional benefits.
The green roof concept is akin to the popular, but traditionally heavy and
difficult to maintain roof garden found atop buildings worldwide. Roof gardens
are nothing new. Gardens for the enjoyment and relief of city dwellers have
existed atop buildings for decades. Such roof gardens are expensive to build,
often require modification of the structural system of the building to support
the increased load and are fairly high in maintenance requirements.
When it comes to roofing, concern for the environment isnt new either. For
decades roofing choices have had an environmental and energy impact on civilization.
Today, energy efficient and environmentally friendly roof designs are growing
in popularity, as even more and more building owners become aware of how
much their roofing choices can affect the environment as well as their pocketbooks.
Modern green roof systems generally fall into two categories, extensive
or intensive, depending on the type of landscape structural burden. Extensive
green roof systems are designed for lightweight planting burden construction
on flat or sloped roofs. Intensive green roof systems are intended for heavier
landscape construction for flat roofs and landscape planters. There are
distinct differences in the application and design criteria for the load
requirements of each system.
Extensive systems may be installed over any properly designed deck, including
Concrete, wood and steel. Typically a vapor barrier or vapor retarder is
installed over the deck depending on occupancy and local conditions. Over
the vapor retarder or substrate a layer(s) of (optional)thermal insulation
is installed. Mechanical fastening of the insulation may be required depending
on wind uplift conditions, slope, building height and local codes. The waterproofing
membrane and metal flashings are installed to complete the watertight envelope.
Decks with slopes of 8 degrees or more may require the installation of landscape
retainers at the roof membrane elevation. Intensive systems may be installed
over decks designed to accommodate the added load. Typically, concrete decks
are the best design choice.
Eco-roofs are becoming fairly common in parts of Europe, principally in
Germany and the Netherlands, where green roof technology is well researched
and a green roof industry is well developed. The Amsterdam airport has incorporated
a sloped green roof into the design of its terminal building. Some cities
in Germany now require green roofs on flat-roofed buildings; by 1996 over
3.2 million square feet of green roofs had been constructed in Germany alone.
Green roof technology explores and promotes interest in viable solutions
that are aesthetically, functionally and environmentally friendly. It addresses
the urgent ecologically demanding issues of air and water quality and storm
water management. Green roofs help to invest in the protection of our environment
by diminishing developmental impact on our communities while providing a
fresh approach with visually appealing organic architecture. The new paradigm,
variously known as eco-roofs, green roofs or extensive roof gardens, typically
cover the entire roof of a building with a continuous thin growing medium
that supports low vegetation. Eco-roofs are lightweight, modern versions
of he sod roofs that are a centuries-old tradition in Scandinavia. Because
of their light weight eco-roofs require little additional load-bearing capacity
from a buildings structural systems; in many cases they may be installed
on existing buildings with no structural modification. They do not require
flat roofs as do conventional roof gardens but may be installed on roofs
with slopes of up to forty-five degrees if provided with a raised grid structure
to hold the growing medium in place. Additionally eco-roofs typically require
little of no irrigation or fertilizer.
Green roofs create buildings and developments that heal rather than harm
the environment. Green roof structures can become net producers of energy,
clean water and air, as well as part of healthy human and biological communities.
How Green Roofing Works
- Beneath every green roof, a roofing membrane provides the critical
waterproofing layer
- A unique, root-resistant compound prevents plant roots from penetrating
beneath this waterproofing membrane
- A drainage layer draws excess moisture away from the roofing membrane
- A filter layer prevents soil from clogging the drainage system, while
enabling water to penetrate and nurture the plant life.
- Lightweight, specially formulated soil absorbs and retains water in
a controlled manner to nourish the plant life
- A surface layer of plant life is customized to
meet specific functional and aesthetic requirements of individual applications
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