Most houses have a rooftop, but how many of us actually use that rooftop for anything besides shelter. Green roofs provide a space where individuals can have some contact with nature. Such a place otherwise might be hard to come by in a large city like Dhaka!
If possible, green roofs are meant to be experienced and enjoyed. To feel the breeze which may linger with the smell of the first hint of jasmine on a still spring day. To break off a twig of rosemary for the evening's lamb koftas. To lose track of time, engrossed in a good book and the warm winter sun. To barbecue, chat and laugh with friends and family. To engage with and enjoy nature. Some of this you may get with an extensive green roof. But make it a rooftop with intensive planting and all of these experiences become possible.Green roofs have many benefits at the economic, ecological and social levels. The green roof can provide a rainwater buffer, purify the air, reduce the ambient temperature, adjust the indoor temperature, save energy and promote urban biodiversity. The green roof can be part of the weatherproofing of the building. Besides, people are happier in a green environment than in a gray environment. Let’s look at a few points on the benefits of rooftop gardens given below:
Provides rainwater buffer:
The green roof absorbs rainwater by buffering the moisture in the plants, substrate and drainage layer. This delays the discharge of rainwater into the sewage system purifies rainwater and the water evaporates through the plants. These all help stabilise the groundwater level, reduce the peak load of the sewage system and reduce the risk of flooding.
Purifies the air:
Plants in green roofs filter out particulate matter from the air and convert CO2 into Oxygen. With a green roof, you will contribute to air purification.
Reduces the ambient temperature:Plants absorb sunlight, absorb 50 per cent and reflect 30 per cent; therefore, they help create a cool and pleasant environment. For indoor climates, this means that the air conditioner does not have to work so hard, which in turn means energy saving. This also has an additional positive impact on the climate near the building and the temperature of the city. Overall, this means that the temperature in the city will drop.
Direct-green, low maintenance:
Using vegetation blankets, you can create a green roof with a direct green effect. The mats are carefully pre-cultured, and the coverage rate reaches 90 per cent upon delivery. This means that it is difficult for weeds to take root, and the maintenance required is negligible.
Increases solar panel efficiency
A green roof reduces the temperature on the roof. Thanks to this cooler roof, the efficiency of solar panels is higher and so you reduce your total energy costs.
Reduces ambient noise outside and inside:
The green roof has a sound insulation effect on your building. It absorbs sound, thereby providing a quieter environment inside and outside the building.7
Extends life span of roof:
A green roof protects the roofing material from external influences such as the sun, rain, wind and temperature fluctuations and doubles or triples the life span of your roof to up to 60 years or even longer. You will recoup the investment in your green roof within 8 to 21 years.
The sedum, herbs, grasses, or host plants contained in the green roof can promote the habitat of birds, butterflies and insects, especially in the urban environment mainly made of concrete and asphalt.
Creates a fire-resistant layer:
Plants naturally contain a lot of moisture. With a green roof, you create a natural fire-resistant layer on your house or office building.
Increases the feeling of well-being:
Living and working in a green environment has a positive effect on the well-being of people. Greenery offers relaxation and reduces stress.
Offers healing environment:
Greenery encourages faster recovery for patients, resulting in a shorter hospital stay. A person’s tolerance of pain is higher in a green environment. It is also known as a ‘healing environment’.
More social interaction, less vandalism:
Working or living in a green environment brings people together. The green environment can provide higher perception and user experience. This has a positive impact on the social cohesion of the community. Areas with higher levels of greenery are less affected by aggression, violence and vandalism.
Saves time and money:
In contrast to planting a green roof with individual plug plants, laying a green roof using vegetation blankets is quick and easy to realise. And the subsequent maintenance is minimal. That means you save time and money!
Roofs exposed to a great deal of wind pre-cultivated vegetation blankets ensure that the substrate will not be blown away in a storm. These provide a solid and erosion-resistant top layer to the green roof.
If we create a green rooftop, it becomes a balancing act between greenery and habitable spaces. Our philosophy should be to let the plants win. With this strategy, the rooftop garden feels more like a private oasis, with lush plants surrounding the nooks to relax in and the opportunities are endless. Giving the plant's priority and fitting other functional spaces around is the difference between a roof terrace with a few pot plants dotted around and a successful, thriving rooftop garden.
The writer is a USGBC Faculty Member