2. Green roofs
3.1 Components of a green roof
3.2 Types of green roofs
3.3 Benefits of green roofs
3.4 Design considerations
3.5 Health and safety
3.6 International design
3. Green walls
3.1 Types of green walls
3.2 Benefits of green walls
Green or living roofs are those that are purposely fitted or cultivated with vegetation. It is important to understand that there are different types of green roofs and each performs and looks differently, as they provide different habitats and impact energy and performance different ways. The main types of green roofs are either extensive (planted with simple plants such as sedum) or intensive (planted with shrubs and even trees). They can provide such benefits as improving air quality, fire protection and stormwater management. Green roofs were common within the UK and Europe industrial revolution began. Renewed interest developed at the end of the 19th century in Germany where they were used for their fire protecting properties. (1) At present there are no specific British Standards relating to green roofs. However the German FLL standard is being used by British suppliers as well as the UK green roof codes of practice. Green Walls
Green or living walls are walls covered in some form of vegetation. Generally they are comprised of climbing plants and are designed so as to support such vegetation. These walls are now being constructed to provide an additional structure to which vegetation can actually be planted. Depending on the species used living walls can provide environmental benefit such as biodiversity, thermal insulation and cooling benefit to the building. Components of a green roof
A green roof will be made of these four main components
* The vegetation layer
* The substrate
* The drainage layer
* The root barrier
The vegetation type will depend on the design goals for the roof and site conditions. There are four main types of vegetation on a green roof vegetation mats, plug planting, seed and cuttings and natural colonisation (allowing a bare substrate to colonise naturally). The substrate
The purpose of the substrate layer is to provide nutrients, mechanical strength, open pore structure, chemical composition and drainage properties. They can be made up to suit different vegetation types and can vary in depth depending on the type of green roof.
The drainage layer
The drainage layer controls, along with the substrate, the level of water retention of the roof. The purpose of this is to maintain the correct conditions to allow plants to survive, control the amount of stornwater runoff and reduce the risk of water ponding. The local climate must be taken into consideration for design of the drainage layer. The root barrier
The root barrier prevents the plants penetrating through to the waterproofing and damaging the membrane. The type of root barrier will vary depending on the system and the type of plants that are used. This root barrier can be applied on top of the waterproofing with a heavy grade polythene based material or provided within the waterproofing. Types of green roofsIntensive green roofs
The substrate depth of an intensive roof can vary from 150mm to 1500mm. The vegetation used for these roofs can include herbaceous plants, grasses, shrubs and sometimes even trees. Intensive roofs can allow for human access if safety provisions have been made and can be compared to a park at ground level. The weight of this type of roof can be significant due to the size of plants used, the depth of the substrate and the volume of water that it retains. As a result of this additional weight inclusion for reinforcement or extra building structural support may be necessary. Intensive roofs require a lot of maintenance, regular irrigation and fertiliser.
Simple intensive green...