Green Roofs are also known as Living Roofs or Eco-Roofs.
Sods or plants are used a well-researched sustainable design methodology
to provide a water tight, sustainable roof surface. Whilst green
roofs are common in under-developed countries, their introduction
to the modern building practices is providing an exciting new development
in the sustainable building movement, and gaining in popularity
across the world.
Types of Green Roofs
There are two basic types of green roof:
Intensive Living Roofs - using plants between
1 to 15 feet high, including shrubs and trees. This type of planing
requires deep levels of soil, and thus a heavy weight-loading
roof. Due to the high level of ongoing maintenance and extensive
irrigation required, this type of green roof is generally not
suitable for domestic buildings.
Extensive Living Roofs - use only low-lying
plants from 2 to 6 inches high. Only a few inches of soil is needed
- and only a low weight-loading roof. Plants are specifically
selected for their sunlight tolerance and low maintenance.
Both types of green roofs can be used for flat or pitched roof
construction up to 45 degrees. Sloped roofs require design elements
to allow for impact on drainage and soil loss.
Constructing a Green Roof
A green roof system consists of layers to allow for a natural
growing environment whilst also protecting the building and roof.
There are four main layers:
Standard metal roof top
Root repellent membrane
Filter cloth -to allow water to drain but prevent soil escaping
Foam - creates a moisture blanket to ensure sufficient water
retention for plant life
Drainage system - to drain excess water
Soil substrate - recycled aggregates such as crushed porous
4 inches of lightweight and free draining soil with good moisture
Video - Green Roof Construction [3:00]
Plants should be low growing, rapid spreading, drought-tolerant,
with a fibrous root system (to protect roof membranes). They should
also require low nutrient levels to minimise care.
Allergen free native species are ideal, as are short perennials,
wildflowers and succulents.
Benefits of Green Roofs
There are a number of social, economic and environmental benefits
to green roofs, including:
Increasing home energy efficiency - cooling in summer, insulation
Moderate temperature - lowering overall ambient air temperature
outside as well as moderating the heat within the home.
Filtering and cleaning toxins from both air and water
Attract local bird life - preserving and enhancing biodiversity
Reducing carbon dioxide emissions
Retain rainwater before it evaporates - reducing flooding
Reducing urban temperatures and associated smog
Insulating against sound / noise
Providing aesthetic appeal and 'green space' recreational opportunities
Using recycled materials like aggregates and plastic sheets
Green roofs are growing in popularity, with over 10% of houses
in Germany with green roofs. Many countries are integrating green
roofs into their building standards and regulations. Some even provide
subsidies and incentives.
With current growth of 10-15% in Europe, and increasing interest
worldwide, green roofs are becming an increasingly important option
for builders and planners.