Green Roof

Green Roof

This document is organized into the following categories:
* The Roof Garden – an overview of the roof benefits in urban environments.
* Why Have a Green Roof – examination of ecological, technical and financial benefits.
* Garden Roof Assemblies –breakdown of the various components assemblies.
* Water Management – synopsis of water retention and releasing storedwater benefits.
* Design Considerations – description of the various advantages for green roofs.
* Specifications –specification and resources based on individual project needs.

Green Roof Benefits

The Green Roof provides building owners and tenants with many ecological, technical and economic benefits. Some of the advantages include:

Ecological Benefits...
* Enhancesbuilding's appearance
* Mitigates the “Urban Heat Island” problem
* Reduced Energy Costs - reduce heating and cooling costs from 25%-50%
* Processes airborne toxins and re-oxygenates the air
* Creates therapeutic and peaceful environments
* Natural Habitat for Animals and Plants

Technical Benefits...
* Additional Thermal Resistance
* Reduced noise levels - improvesound insulation from 3 dB by up to 10 dB
* Require minimum maintenance
* Reduction of Dust and Smog Levels
* Reduce the risk of flooding, sewer overflows, and subsequent discharges
* Stormwater management - retain 50%-90% of a typical rain fall on the roof

Owner Benefits...
* Extended Roof Life
* Additional Usable Space
* Building Incentives - government agenciesprovide incentives
* Adds space for tenant use and recreation

When the outside air temperature reaches 80 F, surface temperatures of traditional black rooftops can be as high as 180 F. Rooftop heat loads affect the amount of energy necessary to cool buildings to desired temperatures. Because of their insulating properties, green roofs significantly reduced rooftop heat loads in warm seasons,reducing the amount of energy needed to heat and cool buildings effectively, even more than reflective white roof membranes.

The urban "heat island" effect occurs in most of the large cities of the world. Roads and building rooftops absorb a significant amount of heat during daylight hours. This heat, in turn, is radiated back into the atmosphere, causing further warming. These factors canresult in a 6- to 10-degree temperature increase in large cities. Green roofs help to insulate and shade buildings. Also, through evapotranspiration, plants cool the atmosphere around them, significantly reducing the urban heat island effect within these cities.

Green roof systems serve as excellent sound insulators. Green roofs protect exterior roof membranes from ultraviolet radiation, extremetemperature fluctuations, punctures and other physical damage. They can significantly increase life expectancies of roof membranes, diminishing the need for costly roof replacements and maintenance. Especially in urban areas, over 75% of a rain event can become surface runoff leaving pollutants into waterways. Green roofs help relieve this problem through retention of rainfall and confinement of roofwater runoff.

Cities are encouraging green roofs to reduce storm water surges. For example, the City of Portland, OR, is leading an aggressive regional program providing financial, technical, and educational incentives to participants in its green roof initiative; Minneapolis, MN, confers green-area status to green roofs; and Chicago, IL, provides a density bonus for the use of green roofs inits central business district. Other cities have also implemented incentive structures, including tax credits and avoidance of fees assessed for impervious surface cover.

Green Roof Assemblies

The Green Roof is suited for locations that will receive little or no maintenance, or where structural capabilities are a concern. Recommended plants include sedum, herbs, grasses and other...