As well as looking beautiful without the need for regular maintenance, green roofs perform vital environmental functions such as providing a place for insects, birds, wildlife and other plants to breed and germinate. If all of the flat roofs in London had Green Roof Coverings, the air would be so much cleaner.
Green Roofs also store rainwater and can slow down the rate of storm-water during flash rainstorms, and prolong the lifetime of your roof coverings. The reduction of rain into the storm drain system ensures that it is recycled naturally. Many towns and cities have a combined storm and sewer system which means that all water going into the storm drains has to be processed through the sewerage system and is treated with chemicals.
Green roofs in Cities and urban areas also rely on green roofs to replace much needed green belt land which is used up for building new houses.
Because our Green Roofs prevent the sun's rays from reaching the roof covering, its life will be prolonged even more due to the extra protection on its surface. A weatherproof membrane is laid onto the roof covering before the Sedum or other type of Green layer is introduced for added protection. This will reduce the temperature that the roof surface rises to in the summer.
A Green roof installed in Portland, Oregon has been installed and its underlying roof coverings have not been maintained since 1975.
There is quite a bit of evidence to support the suggestion that Green Roofs also help to reduce the amount of heat loss and heat entry into buildings in the winter and summer. This is a huge benefit in urban areas where the temperature and humidity is often greater than it is in more rural areas. This helps keep heating bills down and reduce the amount of money spent powering air conditioning units
Types of Green Roof
The 2 main types of Green Roofs used in the UK are Extensive Green Roofs and Semi-Intensive Green Roofs. Green Roofs can be installed on most flat and pitched roofs.
Extensive Green roofs are usually made up using mosses, Sedum, succulents, Herbs and a few grasses. Extensive Green roofs do not require any watering as they hold the rainwater and release it slowly. These are classed as a low-maintenance roof and are generally low in cost to install. Typical weights of an Extensive Green Roof would be around 3-5 inches high (75mm - 125mm), and weigh 65kg per square metre. New module style sedum comes in plastic baskets and is laid in a grid, these roofs can be as low as 48kg per square metre.
Semi-Intensive Green Roofs contain more perennials along with some Sedum, Grasses, herbs and Shrubs. The average height of the plants would be between 125mm and 175mm weighing between 100 and 165 kg per square metre. Some serious consideration to the structural capacity of your roof should be given with these roofs. Irrigation will be needed during dryer spells with this type of Green roof and both maintenance and costs are classed as medium with this type of Green Roof Covering.
The other type of Green roof is Intensive. This would be normally found on rooftop urban development and can contain turf and small trees.