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Sustenance Roof...

Updated: Jun 7, 2020

Happy world environment day. Perhaps the "Environment" has more share in the days than anything else in the list of days we observe. For example, we have the 'World water day', 'world earth day', 'world biodiversity day, 'world ocean day', and so on. But the irony is, it is the "Environment" that is most misused and abused in spite of so many days in the calendar dedicated to observe and celebrate its magnificence, beauty, and grandeur.

We are today seeing the downside of globalization. Heavy dependence on foreign oil, goods, and services are hurting our economy. We are today realizing the perils of long-distance movement of food and other essentials. Materialistic living, heavy consumerism, unhealthy (and expensive) food habits are a result of infinite choices, which we have, fortunately, realized is not the best thing to have.

The word sustainability, in my opinion, has more relevance now than any other time in the history of mankind. COVID Pandemic has shown us that we cannot take the environment and economy for granted. Call for #atmanirbhar bharat could not have come at a better time. It is high time that we look at hybrid decentralized models of living (and perhaps development).

But the question now is what is sustainability. We hear this word hundreds of times every day. But what exactly does it mean to be sustainable? Is it measurable? Is there an index for our sustainability?. This is no doubt a difficult question. However, the following will give a kind of simple implementable definition.

"The paradigm of development where progress is achieved in all spheres of life and in all segments of the society where resources (Natural, Social, Biological and economic) are used in a manner in which its quality and quantity are not compromised for the future generations."

One of the ways of achieving this sustainability at a very local and decentralized level is to produce most of your essentials rather than buying it. This way you have more control over the quantity and quality of the inputs used and outputs produced and its respective environment footprint.

At a larger scheme of things, from the individual perspective, minimalistic living, consuming less and simple lifestyle contributes qualitatively to one's sustainability (and adds a lot of purpose and value to one's life).

I have been experimenting with both of the above for over a course of time in my home.

I have been working on a model where my roof must meet most of my water and energy needs. In my opinion, this is as de-centralized as it can get. I call it the "Sustenance roof". Though I have not been entirely successful I have made some headway into this. I am writing a gist of my journey so far.


1. I have a roof area of about 105 SqM, considering Bangalore’s rainfall of 970 mm, I get about 970.00 x 0.85 x 105 = 86,672 say 86,500 liters of water per year.

2. As a family of 3 plus significant floating population and a decent rooftop garden, our daily water consumption is about 430 liters.

3. With a rainfall of 86,500 liters, this translates to (86,500/430)= 201 say 200 days of water requirement or about 54%.

4. More importantly, we put a portion of this water collected into the aquifer through a recharge well. This will over a course of time saturate the groundwater and the water will start yielding from the well. So, in a few years, we hope we will be self-sufficient with water.

Sustainability Check (Water):

  1. About 50% of the water that we consume falls right on our head. That means it is replenishable and this 50% of the water that we do not take from the grid can be supplied elsewhere thus adding to equitable distribution.

  2. Avoiding long-distance transmission of water saves the energy associated with it.

  3. With the underground aquifer getting recharged over a course of time, we may not need any water from the grid. This will complete the cycle. Thus we replenish the quantity of water and increase its quality too.

  4. Most importantly, the rainfall falling on our roof is the purest form of water. Thus we consume water in its purest form with the least possible conveyance.

Energy :

1. With a family of 3 plus a floating population, our daily requirement is about 5 units of energy including cooking.

2. We have the following to meet this demand

A. A 3KW rooftop solar PV system

B. A 150 Liter solar water heater.

3. Our solar PV power system produces an average of 12 units per day that is more than double our requirement. So we end up selling about 50% of the energy that we produce.

4. Since the cost of energy from the solar PV system is much lesser than LPG, we have switched to electrical cooking or induction plate for cooking. So our LPG is mostly for emergency purposes.

5. Since the solar thermal line is also connected to the kitchen, water used for cooking is preheated to a certain extent. This reduces the heating load of induction stove or LPG

6. We plan to install a biogas unit to completely eliminate LPG.

7. Heat seal white paint on the roof keeps the house cool and reduces the air conditioning requirement to a maximum of 20 days in a year.

8. Of course, no electricity is used for hot water required for bathing since the solar water heater takes care of the hot water required for bathing.

Sustainability Check (Energy):

  1. All our energy requirements are met by renewable energy.

  2. The transmission of this energy is not more than 5 meters.

  3. We also just consume less.

  4. Arithmetically we produce more energy than we consume.

  5. Not only we consume energy from renewable sources, but we also push excess renewable energy that we produce back into the grid (@ less than market prices).

  6. Both in terms of quality and quantity, this model seems to pass the sustainability check.

Waste :

1. All the kitchen waste goes to our kitchen composter.

2. All the garden waste goes to our leaf composter.

Both the kitchen waste and garden waste is converted into beautiful rich compost which gets into our little garden.

Sustainability Check (Waste):

1. No wet waste leaves the house. All the nutrients are recovered and reused.

2. Plant nutrition is locally produced without spending energy on production and transportation.

3. Plastic and non-bio-degradable waste however are given out for recycling. (we are not sure how much is actually recycled).


We are far from self-sufficiency in so far as nutrition is concerned. I tried growing ragi and rice on the roof without much success. However, the following experiments have been fruitful.

1. The rooftop garden gives us enough leafy greens once in two days.

2. About 10 to 12 days of vegetable requirement like brinjal, ladies finger, tomato, etc are currently harvested from the garden

3. Papaya tree which is very easy to grow gives us an average one large fruit every four days. Two papaya trees can theoretically feed a family.

5. An added advantage of a rooftop garden is that you have full control over the inputs to the plants and absolutely sure what you are harvesting.

6. One is also consuming fresh and pesticide-free vegetables.

7. Most importantly growing your food is fun and a spiritual exercise.

8. The leaf composters and kitchen composters complete the nutrition cycle and the so-called waste gets back into the garden.

Sustainability Check (Food):

1. About 50% of our vegetable requirement is met right on the roof.

2. Not only the food, the water required for growing the same also falls on the same roof.

3. The manure and the nutrient input for the plants are from the kitchen in which the same vegetables are cooked.

4. It is a long way for food sustainability. However, it is a start.

Bums on the saddle :

Using a bicycle for running local errands can save expensive imported oil and at the same time reduce noise and air pollution. it is good exercise too.

Bangalore roads are really not bike-friendly. However, I am trying to use the bicycle at least for local commutes.

Bio-diversity :

Thanks to some of the above initiatives and the presence of many trees around, we are able to attract some common birds in the neighborhood.

Observing the bio-diversity is a wonderful way to stay grounded and connect yourself to the larger scheme of things (and perhaps discover if at all there is a larger scheme of things).

Apart from the above initiatives, we are practicing the below quite regularly ;

1. Plant at least 2 trees a month in any open space anywhere.

2. We are trying to consume as little as possible. For example, we have stopped buying fancy electronics, fine dining is almost stopped, we are reducing car travel, all the members in the family use cycle, buying stuff from the local store, etc

All of the above are baby steps. We as individuals, as a society and as a nation have a long way to go. As mentioned earlier sustainability is now more relevant than any other time in the history of mankind. COVID pandemic has given us an opportunity to relook at our paradigm of living and developing. It will be prudent to introspect and mend our ways before it is too late.

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