Roofs, rain and recycling of precious water
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The way to transform a city is to transform the way we design our roofs.
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RECYCLING ON THE SPOT: Not a drop of `waste water' need go out of the roof.
Every building has a roof. An poorly designed roof simply acts as a heat sink, capturing the sun and radiating it into the house, making it uncomfortable and calling for cooling devices such as fans and air conditioners. A smart roof, however, can take all the natural resources endowed, convert it into an asset and help drive the house itself.
A city when looked from above is about 40 to 50 per cent roofs. The way to transform a city is to transform the way we think, design and work our roofs.
Consider this:
Water: A 100 square metre roof area receives anywhere between 90,000 to 100,000 litres of rainwater in Bangalore.
All this water can be used productively by storing or recharging it.
A bathroom located on the roof can be designed to separately collect grey water from the washing machine and from the bathwater. This water can be treated on the roof and reused to grow vegetables and plants on the roof itself.
It is also easy to dry clothes washed on the roof using the sun’s energy.
An Eco-san toilet built with a light material such as bamboo can be located on the roof. This will collect solids and liquids separately. The liquids are excellent fertilizers for plants and can be used up on the roof garden itself. The solids can be composted again on the roof and after enough decomposing time can be applied on the roof garden.
Not a drop of ‘waste water’ need go out of the roof.
Energy: The same roof receives enough sunlight to supplement or replace cooking, water heating, lighting and other energy needs.
A solar cooker of the box type or the parabolic concentrator type can cook for you most days in a year. Keep that on the roof.
A solar water heater can meet hot water requirements of the house for most of the year. Sizing depends on the needs and can vary from 50 litres to 500 litres. A solar water heater is best kept on the roof and properly oriented.
Solar photovoltaic systems can provide all lighting requirements of the house in conjunction with LED bulbs or CFL bulbs.
The photovoltaic panel is ideally placed on roofs to collect and transfer solar energy to batteries for storage.
Composting: Kitchen waste can be segregated and the biodegradable part composted in such a device as the ‘Khambha’ composter on the roof. Since there is adequate sun and ventilation the decomposition and conversion to compost is faster on the terrace.
Cultivation: Since there is adequate light and water, a roof is a great place to cultivate vegetables, fruits and yes, even paddy. Using the grey water from the clothes wash and bath, a nice crop of food for the kitchen can be raised. A small poly house helps protect the plants and crops against the vagaries of the weather and enhance productivity.
How about a small fish pond to raise the fish that you want to eat?
This is absolutely possible on the roof. How about raising nutritious algae such as spirulina? A small water body on the roof will do this too.
Biodiversity: So you want to get some birds and bees and butterflies and be in their company for some time of the day or week?
A small water body, plants with a lot of flowers like a creeper and some foodgrains will bring them flocking.
String up a mosquito net on a cot in the non-rainy days and be prepared to experience the stars. Do not forget a blanket; it does tend to get cold in the early mornings.
Smart roofs can do a lot of things and in the process keep the house cool, mitigate the impact of flooding, reduce your ecological and carbon footprint and provide water, food, energy and ecological security.
Get yourself a smart roof and yes, any old flat roof can become a smart roof with a little bit of planning and about half-an- hour of your time every day.
Try it. This is being water wise.
S. VISHWANATH
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