Green Living Roof

Green Living Roof

Green roof

Green roof

By Geoff Davis

A green roof (also known as a living roof) is a growing system built on top of a protected waterproof roof. The growing system can be grass, plants, small herbs, etc.

Many benefits. The main ones are:

  • good for small animals and plants
  • add greatly to biodiversity within the immediate local urban environment
  • create extra green open spaces.
  • prevent flooding as water run-off is reduced and slowed down
  • absorb carbon emissions

Water retention is a big factor in urban areas as many gardens are concreted over, paved over for carports, or decked for play areas.

Decking and tarmac greatly increase run-off rainwater. They provide diverse habitats as they can be planted with indigenous flora for bird, insect and arthropod populations. A green roof modifies the urban micro-climate.

Plants cool the air through transpiration, and reduce surface roof temperatures by as much as 40 degrees centigrade in the summer, given the baking heat on a dark flat roof. They also improve air quality, not only absorbing CO2 but also trapping about 85% of airborne particulates.

Roof gardens lose 30% less heat in winter and are cooler in summer, and also provide sound insulation. A green roof can reduce indoor sound by as much as 10 decibels for every 3 inches of growth. Green roofs have been shown to reduce heating costs by as much as 25% and cooling costs by as much 50%, for the floor directly under the roof.

The subsurface protects the roof against aging and replacement. They also add value to a house or building. They look very attractive compared to traditional grey slate or asphalt roofs, and provide a soothing effect for the stressed urban person.

What is a green roof? The subsurface is a high tech system that holds water for dry periods. There is also a waterproof membrane to prevent leaks. They can be very heavy, from 80 to 365 kilograms a square metre . This means most roofs will have to be structurally reinforced.

Amazing fact:
A recent study by US company Weston Solutions estimates that greening the rooftops of all buildings in the City of Chicago would result in nearly $100 million of annual energy savings.

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