Green roofs can be divided into the following types; extensive, semi-intensive, intensive and brown/biodiverse.Roofs covered by vegetation offer aesthetic, environmental and economical benefits. The vegetation in most cases comprises hardy, short growing, self-renewing species of grass, sedum, heather, or bushes that can withstand soak and drought during long periods. Green roofs reduce noise in the environment due to a sound absorbing surface. They also absorb noxious exhaust fumes and carbon dioxide as well as produce oxygen.
Extensive Green Roofs
Extensive green roofs are not usually accessible and therefore the management level required is often significantly less. Plant types selected are more naturalistic and self-reliant often surviving on a thin soil or substrate layer. This, compared to intensive green roofs, can allow for reductions in the overall self-weight of the system and could be regarded as a lightweight green roof.The costs of establishing extensive roof gardens are lower than of intensive ones.
Semi-intensive Green Roofs
Semi-intesive green roofs exhibit intermediate characteristics. Whether irrigation is necessary or not depends on the regional climate and on the kind of plants that are used. Maintenance is still quite labour intensive because the design of most semiintensive green roofs is still garden-like.
Intensive Green Roofs
Intensive green roofs are usually accessed by people in a similar way as to any garden or terrace, and as such, require an intensive level of maintenance. Soil depth or substrate depth is usually thicker and often they require artificial irrigation. Selection of plants is important and the supporting structure must be capable of supporting the additional soil or substrate loading.
Brown/Biodiverse roofs are designed to replicate brownfield land which has been left to naturalise and become a home for a variety of birds, insects and other wildlife. Crushed brick and rubble form the main components of the substrate and often logs and stone piles are added to provide nesting areas. These roofs are either left to naturalise or can be assisted by overseeding with wildflowers.
Both GreenGrid and Prelasti are tested and approved for use as a waterproofing membrane under vegetation and green roofs. The GreenGrid system was developed and designed by engineering, roofing and horticultural experts to produce an efficient, integrated green roof product, consisting of a modular design that arrives at your site pre-planted and ready for installation. Prelasti is a roofing membrane based on EPDM, where both the membrane and the seams are root resistant, resulting in superior longevity (service life exceeds 50 years) and low impact on the environment. Prelasti membranes are chemically stable and do not release any substances that could harm the environment during its service life.
Benefits of Green Roofs
- Helping Nature. By adding a green roof to a building, not only does it provide a much more pleasing visual effect, it encourages wildlife such as birds, insects and other creatures into areas which may have been lost due to building construction. The plants also provide filtration of the atmosphere in the most natural and pure way resulting in improved air quality. Careful planting can help buildings blend in with the surrounding environment.
- Extended Roof Life. By covering the roof surface, the waterproofing is protected from UV radiation and weathering. This can greatly extend the service life both of existing roofs and new build.
- Sound Insulation. The growing medium, plants, and layers of trapped air serve as excellent sound insulators. Tests have shown that green roofs can reduce the indoor noise pollution from outdoor contributors by as much as 10 decibels per every 75mm of soil media.
- Stormwater Management. Green roofs help alleviate stormwater runoff through retention and detention of rainfall and detention of runoff from roofs. This benefit can cut costs associated with required municipal on-site stormwater retention.
- Reduced Urban Heat Island Effect.The Urban heat island effect occurs in most of the large cities of the world and has actually been shown to change weather patterns in some. Roads and building rooftops absorb a significant amount of heat during the day, which in turn is radiated back into the atmosphere, causing further warming. Green roofs help insulate and shade buildings. Plus, the plants on the green roofs transpire, cooling the atmosphere around them.
- Reduced Energy Costs.When the outside air temperature reaches 35°C, traditional black rooftop surface temperatures can be as high as 80°C. The heat load of a roof impacts the amount of energy necessary to cool the building to the desired temperature. Due to their insulating properties, green roofs can significantly reduce the heat load of the roof in warm seasons.