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Types of Green Roofs

Page history last edited by Charlene 17 years, 3 months ago

Types of Green Roofs

 

What are Green Roofs?

 

A green roof system is a 'contained' green space on top of a human-made structure. The extension of the existing roof includes a high quality water proofing and root repellant system, a drainage system, filter cloth, a lightweight growing medium and plants. Green roofs can be installed using modular sections or created at the site.

 

Although green roofs are more expensive to install, they last twice as long as a normal roof and confer many more benefits to industries and communities.

 

 

 

Green roofs can provide a wide range of public and private benefits.

 

Green roofs provide the building owners with a proven return on investment and a significant opportunity for social, economic, and environmental benefits, particularly in cities.

 

However, in North America, green roofs are a vastly underutilized technology and there is huge potential for market expansion. Although efforts of several industry leaders have been made, the technologies are still poorly understood, unlike in Europe where green roofs have become very well established. Currently, there is a multi-million dollar green roof industry in Germany, France, Austria and Switzerland. The industry continues to experience growth, both in millions of square metres of green roofs and in the market for green roof products and services. In Germany, for example, the number of green roofs constructed increased from 9 million square metres in 1994 to 13.5 million square metres constructed in 2001.

 

This has been a direct result of government legislative and financial support

 

In BC, the Community Charter and Local Government Act allows vegetated roof systems. However, there should clearly be policies enacted to increase the number of green roofs built in Vancouver, and more specifically, at the SE Marine Drive site.

 

 

Green roofs typically fall into two categories:

 

1. Extensive Green Roofs:

  • What is it?: Low-maintenance ground-cover system

 

  • Where is it ideal for? Large flat-roof buildings and apartments and sloped residential roofs.

 

  • Vegetation planted:: Desert grasses and succulent plants are embedded in three-six inches of lightweight growing media.

 

  • Maintenance:After one year, they do not require watering although annual spring weeding of tree seedlings brought in by birds is needed.

 

  • Example: The Vancouver Convention Centre will have 2.4 hectares of very low maintenance green roofing in preparation for the 2010 Olympics.

 

 

2. Intensive Green Roofs:

 

  • What is it? Fully landscaped roof top gardens that can accommodate many uses

 

  • Vegetation Planted: Diverse plants and trees are planted in 8-12 inches of soil amid features such as walkways, railings and lighting. Parks, playgrounds or vegetable gardens are possible.

 

  • Maintenance: Requires regular maintenance.

 

  • Example: In Greater Vancouver, Electronic Arts has a rooftop park, while the Vancouver Fairmont Hotel grows herbs on its rooftop for the hotel kitchen

 

Intensive vs. Extensive?

  • Although intensive green roofs may require extra costs, they may confer more benefits
  • Extensive roofs are less expensive to build and maintain
  • Depending on how thin the profiles are, some extensive green roofs may not require extra structural support
  • A cost-benefit analysis for an intensive roof must be done on a project-by-project basis

 

 

 

 

PolicyExtensive Green RoofIntensive Green Roof
Soil Depth8-25 cm (3-10 in)25-100 cm (10-40 in)
WeightLessMore
UtilizationLess DiverseMore Diverse
SpeciesLess DiverseMore Diverse
Opportunity for Urban AgricultureNoYes
Low Maintenance and IrrigationYesNo
AccessibilityLowHigh
Code ComplianceMinimalWalkways, railings, lighting, access

 

Sources:

 

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