It is already known for the green building must have the green roof which the grass and the trees on the roof are the best show case to visualized the green of the building. The green roof is surely an environmentally friendly alternative to a conventional roof.
Beside its green look, the green roof adds insulation, reduces the amount of construction debris from shingles, and creates a more usable area out of the same space. In the bigger picture, creating green roofs can add more green space to an urban environment which help reestablish former ecosystems that were lost during the constructions and urbanization. During these times, the harmful effects of city construction and maintenance on the existing ecosystem were given little thought. Birds and insects were driven out or forced to survive in urban cityscapes, altering their natural behavior. Green roofs can provide extra living space for animals, restoring balance, and encouraging them to feed on their natural prey instead of human by-products or waste.
However, to build a green roof is not simple when needed to place the layer of soil on the roof and then plant the vegetation over it. With the proper engineering, green roof requires the multiple layer of materials, beginning with a waterproof layer which could be coating or membrane type, to prevent water from entering the roof top of the buiilding. The root barrier is placed on top of the waterproof membrane to stop roots from attaching themselves to the house. Then, the drainage system is constructed providing the drain from excess stormwater and the blanket to prevent the soil to cloak the water drainage. And then, the top layer of the soil ranges from 10 to 30 cm. in thickness depend on the type of plants which is the final component of the green roof.
It sounds complicate when we think of the whole system of the green roof. To make it easy, there are only 2 components to consider. First, what kind of plants or trees you want to grow, and second, what kind of system or which supplier of the drainage system you need to hire to complete your green roof.
For the plants, it would be more easy and sustainable in the long term to choose the local and native plants that grow in the natural condition around the construction site or in the area. These kinds of local plant will require minimum upkeeping. They also consume the water accordance to the season which reduce the water-use to supply the vegetation. However, please keep in mind that those green roofs are not exactlty the natural condition to the plants. Most of the green roofs are placed on the roof top where the moisture was taken by the wind and sunlight easily. Also the plants require additional fertilizer to keep them grow since the green roof is an isolated environment. And to grow the bigger tree, there must be the higher layer of soil for the root. The design of the green roof's plants will reflect to the design for water drainage and the roof top.
The water drainage system is equally crucial, not only benefit for the green roof, but also effect the building in the longterm. If the system fail, the leaked water could harm not only the things in the building but also ruins the building structure too. My suggestion is to searching for the contractor that provide all the solution for its both system and installation work. Start with the waterproof layer that must be well installed or applied. It will be the deepest part which is very difficult to fix if it fails.
The drainage system must be proper selected to suit the need of water flow. In this case, an engineer can calculate the amout of water that runoff and selected the right products. There are plenty of the subsoil water drainge system then you can find. However, make sure that your contractor knows how to put it right.
Overall of the downside of green roof construction is the high initial cost which surely terrify the owner. However, the investment for the best system is payoff which reduce the chance for a future trouble such as leakage. Also a green roof has the potential to significantly lower costs of maintenance within years after its installation which depend on the kind of plants that grown.
Most of all, the need to have the green roof is the major concern for you. As mention above, the green roof is the symbol of green building, which imply to the luxrious of the project. And if you already decide to put the green roof over the rooftop, it is better to plan from the design stage so that the architects, the landscape designers and the engineering team can prepare for the green roof from the start. On the other hand, you also can prepare for the budget of the green roof from that stage too.