What is Green Roof System?
Green Roofs are Eco-friendly value-adding systems to the buildings by extending the existing rooftop covered with vegetation supported over a waterproofing system along with other layers placed over the roof or sloped roof.
What is the purpose of a green roof system?
The main purpose of the Green roof system is to strengthen/adding value to the existing roof facility without damaging any of the structural components or strength of the roof. It also provides various advantages to the end-user, broadly classified as public, private and design-related advantages which are mentioned in the below sections.
How does a green roof work?
- The overall Process through which the Green roof works is supported by various layers and the working mechanism is depicted below.
This layered mechanism of the green roof system involves the following layers: (1)
- Structural roof support
- Moisture/ Vapor control layer
- Thermal insulation layer
- Roofing membrane support
- Waterproof/ root repellent layer
- Drainage layer
- Filter membrane Layer
- Soil Medium
- Vegetation cover
Structural roof support:
This layer acts as the backbone for the entire structure of the green roof system. This layer provides adequate support by taking the maximum load of all the remaining layers of the system and thus reducing the damage caused by the green roof to the original roof presented. This layer consists of minerals and a lesser amount of organic substance which will be helpful for the other layers.
Moisture/ Vapour control layer:
The vapour control layer acts as a medium between the structural support layer with the other layers and it does not permit the Moisture/vapour to reach the bottom structural layer and damage it.
Thermal insulation layer:
The thermal insulation layer is one of the key layers of the system as it acts as a heat shield by absorbing most of the heat consumed by the green roof system through vegetation and other various layers.
Roofing membrane support:
This is also one of the support layers of the system which acts as a transfer medium between the waterproof layer and thermal insulation layer.
Waterproof/ root repellent layer:
A waterproof/ root repellent layer is useful to restrict the water vapour to reach the bottom layers of the system, thus reducing the impact of dampness on the layers below it. It also does not allow the vegetation roots to further grow through the layers beneath it.
The drainage layer plays a major role in the entire green roof system. This layer contains porous material and is responsible for the entire capillary action between the soil medium and the water provided for the system to grow.
Filter membrane Layer:
This layer filters all the unforeseen material reaching the drainage layer and allows only water that is free from dust and other foreign materials. This will allow faster growth of vegetation cover.
Entire vegetation cover grows on the soil medium provided and the depth varies based on the variety of plants preferred by the individuals. A rich soil medium allows the vegetation cover to grow faster.
This is the topmost layer of the entire green roof system and it varies for every individual based on their requirements. Various vegetation covers available in the market are sedum-mix blanket, sedum-herb blanket, bees & Butterflies blanket, wildflower blanket, place's go sedumtray etc.
What are the advantages of the green roof system?
The green roof system has various advantages like thermal insulation in winter, Rainwater/stormwater buffer which will reduce the peak load on the sewerage system and risk of flooding
in the low-lying areas, reduces the ambient air temperature, extends the life span of roofs, Sound barrier for the building by absorbing the outside noises and stopping the inside noises, Acting as a fire barrier for the building, improves the overall Aesthetics of the building, better air quality for the communities, Acts as a barrier for Electromagnetic radiation for the building, Increases the Biodiversity of the system, Better Quality of life and wellbeing of the people etc.
What are the disadvantages of green roof systems?
one of the major drawbacks of green roof systems is that It has some higher initial investment and depending on the type and variety of plants installed maintenance cost also can be added.
How much does a green roof cost?
The cost of Green roof systems depends on various factors which include total depth of the soil medium, extent/size of the installation, selection of plants, Usage of water and whether the system is to be reachable or inaccessible. The cost of a green roof varies between $15 and $25 per square foot for intensive roofs, and between $10 and $20 for extensive roofs. (2)
This cost includes cost of soil medium, selected plants and transportation expenses are also included.
What are the types of green roof system?
There are mainly three different types of green roof systems available- Extensive, Intensive & Semi-Intensive.
An Extensive Green roof system has a medium to Shallow depth soil profile (generally less than 6 inches) with a very less roof load, Limited choice of plants, basic water requirements, and most often not accessible.
An intensive Green roof system has a deeper soil medium available for plants to grow, which can support various plant types including small trees. They have more structural load than an Extensive roof system and need more regular care and watering of plants. In most cases they are accessible.
The semi-intensive Green roof system has features of both types. The overall depth of the green roof system depends on the structural capacity of the roof, the plants are chosen, Yearly rainfall and stormwater storage need.
A comparison of Large and Thorough roofing system is presented below.
Broad Green roof system
Thorough Green roof system
|Overall weight of the system is low
||Overall weight is high as the soil medium is deeper
|Selected plants only can be grown
||Many varieties of plants can be adopted
|Suitable for sloped roofs (0-300)
||Suitable for flat roofs
How to maintain a green roof system?
A green roof system can be maintained based on the type of system that has been adopted. The initial two seasons are particularly important for the system to grow faster and healthier. Following methods can be followed for maintaining a green roof system effectively.
Removal of unwanted plants:
Soil medium for the green roof systems sometimes having unwanted plant seed mixed with the desired plants thus, they create hindrance for the desired plants to grow. Hence in regular intervals, a green roof system is to be scrutinized for unwanted plant growth.
Adding manure or compost to the soil at least twice a year helps the soil medium and thus the vegetation to grow faster.
Adding a few amounts of water possible:
Generally, for the Intensive green systems, we should provide a minimal amount of water for the vegetation so the overall weight on the roof system can be balanced and maintained. Desert type plants which need less amount of water and light in weight are preferable for the green roof systems.
Check for the Pests and Diseases:
Periodic maintenance checks should be done for green roof systems to verify the pest and diseases caused by them. Early identification of such things helps in reducing the effect caused by these insects so that the entire plantation will not get affected.
Practical Implementation of Green roof systems?
Green roof systems are most often seen in various developed countries as the growing demand for eco-friendly environmental products is increasing.
Various countries in which this is successfully implemented are Australia, United States, Canada, Germany, France, Finland, Greece, Sweden, the United Kingdom etc.
I hope the blog provides you with adequate knowledge of the Green Roof System and its associated features. Please feel free to like, share and comment.
P. Dinesh Kumar
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