April 13, 2008

Landscape- Sustainable South Bronx: Green Roofs

Green Roofs:

A green roof system is an extension of the existing roof which involves a high quality water proofing and root repellent system, a drainage system, filter cloth, a lightweight growing medium and plants.

Green roof systems may be modular, with drainage layers, filter cloth, growing media and plants already prepared in movable, interlocking grids, or, each component of the system may be installed separately.Green roof development involves the creation of "contained" green space on top of a human-made structure. This green space could be below, at or above grade, but in all cases the plants are not planted in the "ground'. Green roofs can provide a wide range of public and private benefits.

"Heat Island Effect":

Heat absorbency by roofs and pavement, air conditioner use, and the power plants that supply electricity for them help to create what is known as the Urban Heat Island Effect. This can exacerbate certain health conditions, and lead to more air conditioner use in a vicious cycle that costs government and individuals money. About 20% of NYC’s surface area is covered by non reflective roofs, so there is plenty of room to work with.


Temperature Reduction and Energy Conservation:

Reduced cooling costs by keeping the heat off the building and increasing the amount of insulation. Improved longevity for the roof by minimizing wide temperature fluctuations and exposure to the elements.

Stormwater Management:

Green Roofs provide a way to prevent overflows by absorbing and holding onto the majority of water that falls on them during a typical rain. This water is then slowly released from the soil and into the atmosphere through the foliage – in a process called transevaporation.

Improved Air Quaility:

The amount of Oxygen produced by one tree with a 16 foot diameter canopy is equaled by the amount of Oxygen produced by a 16 square feet patch of green roof with 15 in. high foliage.
In NYC, it costs over $1000 to plant a small tree that takes years to grow that big, but it costs far less to build 16 square feet of green roofs today.

Vegetative surfaces also trap harmful airborne particulates and keep them from entering our lungs, and can dampen noise pollution too. Pollutants in the air are less harmful under lower temperatures that these roofs maintain.


Retrofitting and existing building with a green roof costs more than a conventional roof, but this investment yields cost savings over time through energy conservation and rooftop longevity. A green roof can also increase the resale or rental value of a property, as well as provide aesthetic enjoyment for you in the meantime.


Sustainable South Bronx:

Founded in 2001 by life-long South Bronx resident, Dr. Majora Carter, SSBx addresses land-use, energy, transportation, water & waste policy, and education to advance the environmental and economic rebirth of the South Bronx, and inspire solutions in areas like it across the nation and around the world.

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