A master plan for the roof can include lots of plants to be grown in boxes, even as home-drip irrigation kits can provide the water required for the plants, says S. Vishwanath

Peak summer and 2.30 in the afternoon is a good time to walk on your terrace with bare feet and learn a lesson on solar energy and heat transfer. If your feet are not toast then you can come inside, switch on the air conditioner and reflect. Up to 85 per cent of the heat gain in a building can be from roofs. The reason that the air conditioner is on is because the roof has become hot and is transferring heat albeit with a time lag. Now switch on your google earth map and take a look at your city. Almost all you can see will be rooftops and a bit of roads.

Up to 60 per cent of a city can be rooftops as they generally tend to be densely built-up. A home gets hot from the terrace and the city gets hot from the rooftops that occupy its geographical space.

Paradoxically and to complete the vicious circle, cities are losing their greenery as trees are chopped to make way for buildings, roads and flyovers. This further heats up the city and demands more energy for cooling buildings and cars.

What can be done about it?

Part of the solution may lie in redesigning our roofs and rooftops. A master plan for a roof can include lots of plants to be grown in boxes. Greens are the easiest and can be planted in thermocol boxes lying around as junk, wooden crates or the conventional pots. These will provide organic ‘methi’, ‘palak’, ‘dhaniya’ for you as well as keep the roof cooler. The more adventurous can place a layer or two of pond-lining plastic sheet material, create a brick rim of about four inches, fill this with a mix of compost, vermin-compost and earth and plant almost anything including rice. Home drip irrigation kits can provide the water required for the plants.

A solar water heater is usually ubiquitous but note that it not only heats water for you but cools the roof below it. Solar photo-voltaic panels can provide energy for lighting and for fans and indeed for the entire home and again cool the roof below it. A solar box cooker or a parabolic cooker can also do your cooking for you and keep the roof cool.

A rain barrel can collect rainwater from raised portions of the roof such as the staircase room. This water can be led into the kitchen, filtered and used for drinking and cooking purposes.

Grey water

A grey water treatment system full of reeds, cattails and plants can clean up your bath water and washing machine water, fill the roof-top with green and provide supplemental water for flushing toilets and for gardening.

Kitchen waste composters can be placed on roof tops, safe from rats and bandicoots, for converting kitchen waste into manure.

A small fish pond of 1 m x 1 m x 1m can grow fish for you to eat if you are a fish eater or allow you to observe ‘koi’ fish and go into a Zen state of mind. This will also keep your home inside cooler.

A bamboo gazebo can be strung up with creepers which can grow flowers as well as vegetables. This will look beautiful, provide for the kitchen, be a good place to sit under and cool the building.

A smart roof can be a productive roof, serve several purposes and reduce energy consumption for a building. It is truly time to be roof-smart in a hot city.