After I swallowed the anchor (a naval term for retirement), I settled down with my wife and two kids in an independent house in a suburb of Bengaluru. I was thrust into managing one’s own resource in terms of electricity, water and waste we generate unlike the days when the navy took care of all this.
My home is designed to be capable of generating its own power with minimal need of utilising power from the grid, and taking care of its water needs through proper conservation techniques, also a cool home which is not energy guzzling.
The principles that constitute a sustainable home can be put in four categories :-
- Energy generation and conservation
- Harvesting rainwater
- Utilising grey water
- Utilising food waste to generate compost and create a garden
So how does one build a self-sufficient and sustainable house on a 30×40 site?
We keep hearing about 30×40 size being too small for incorporating these ideas. But It is very much doable while adhering to the bye-laws and various other conditions laid down in building laws.
- Energy generation and conservation
Energy generation for home use is through implementation of a Solar Roof Top Photovoltaic system (SRTPV). The solar panels are mounted on the terrace on top of a canopy. Typically, 1 kw of panels occupies around 6 sqm (roughly 70 sq ft).
The other accessories and batteries would take less than 4 sq ft and all of them can be mounted on the wall (generally this can be done in the space below the overhead water tank). The canopy, if well constructed, also provides shade to the entire house ensuring that the top floor does not heat up, thus reducing the need for air conditioning.
Other sustainable features such as solar water heater, fans with Brushless DC motors, LED lamps and other energy efficient home equipment ensures that energy conservation is taken care of. Typically, 4 kw solar panels would generate around 16 kw of energy per day and even at 50% consumption, the rest can be exported to the BESCOM grid.
A system of this kind would cost around Rs 5 lakhs. The larger impact is uninterrupted power supply with no dependency on the whims and fancies of BESCOM. This was put to the test during the lockdown with three working members being cooped up in the house and one school going child hogging the internet and the fans running throughout the day.
2. Harvesting rainwater
Water, the precious resource which quenches peoples’ thirst or the boiler’s needs, was always in my mind whilst ensuring the maintenance of various critical assets which generates potable water out of sea water in the Indian navy’s fleet of ships and submarines.
But at home, I turned towards the sky for water. Rainwater harvesting (RWH) is cost effective, simple and effective to meet your water demands. Bengaluru with an annual rainfall of 1000mm in a year would yield almost 75,000 litres of water in a year (allowing for proper construction of the house as per bye laws). A typical home consumes around 500 litres per day, which means the water from RWH is sufficient for five months of usage.
Every house has drain pipes on the roof to prevent stagnation of rain water. All that needs to be done is to connect these drain pipes, filter the water and store it in a sump tank. No house is without a sump and overhead tank. Fitting a water controller ensures that the water is automatically pumped from the sump to the overhead tank.
In an independent house, this can be installed at any time, either during construction or later. Since an existing house is equipped with a sump tank, overhead tank and drain pipes, it’s only a question of connecting the drain pipes through a filter to the sump tank. The overflow water from the sump can be used for recharging the groundwater, or let into the storm water drain to flow to the lakes. This method of rainwater harvesting will not only ensure reduced dependence on Cauvery during the monsoons, but also mitigate flooding of neighbourhoods and also prevent overflow of sanitary lines to which stormwater lines are usually connected. The cost of RWH, filter and ground water recharge pit will be less than Rs 30,000.
Sadly, people are unwilling to take these measures due to lack of knowledge/inertia. But the positive thing is that, people outside the city’s core areas (without Cauvery water supply or largely dependent on borewell/tanker water) have done this in large numbers and have benefitted.
3. Grey water harvesting
My childhood summer holidays were spent in my maternal grandfather’s house in a suburb of Chennai. A two ground plot with a house and large vegetable garden with coconut trees, mehndi, lime tree, canna flowers, roses and a well brimming with water, flashed in front of my eyes. The trick in maintaining this garden was in the intricate network of gutters/moris in which flowed all the grey water generated by washing of clothes, utensils and bathing. The planting of the flowers and trees was done in a manner which takes care of the chemical nature of the water. (Voila! A truly circular ecosystem in the usage of water)
Whilst my grandfather had the luxury of open space for his intricate design of nallahs/gutters in the garden, I had to make do with the small piece of land on which my humble house stood. However, it struck me that I could go vertical. Studying the pipelines, I realised that the sewage water lines and gray water lines were separated. All that was needed was to trap the grey water in a set of drums at the ground floor, filter it and pump it to the overhead tank. Additionally, I connected this tank to all my WCs for flushing purposes.
The fresh water which we use for bathing and washing our clothes runs to the drains after our ablutions. This water is called grey water. Can this be used for any purpose? Yes, it can be. A dual piping system where sewage goes to the city’s sewage network and the gray water into a separate piping system can be put in place at the time of construction of the house.
The grey water is trapped in tanks and filtered and pumped to a separate overhead tank. This water can be used for watering plants and also for flushing purposes.
A family of four generates around 150 litres of grey water per day. So what is the impact? Since grey water, rather than fresh water, is used for flushing, almost 25% water saving is achievable. So the daily consumption of water will reduce from 500 litres to roughly 400 litres per day which means your harvested rainwater lasts for one more month.
In terms of monetary saving, I saved the cost of water tankers which would have been required for the purpose of flushing the loo. What a waste of fresh water for flushing purposes! Instead the grey water powers the loo and also waters the garden on my terrace.
On implementing this, my wife insisted that the quality of water was not good as it was using chemical soaps and detergents. This point was reinforced by my son, a chemical engineer who talked about the ill effects of SLS/phosphates, etc. Her long held desire to convert me to using organic soaps for bath and organic detergent for washing clothes fructified. Thus the grey water system with organic contents was born. It has served us well for five years.
4. Utilising food waste
My wife’s green fingers acquired from her paternal grandfather stuck roots in the form of 150 pots on the terrace of our home, where she grows vegetables. Besides water, this vegetable garden required other nourishments too, which was made possible by looking inwards to food waste.
Food waste, instead of being dumped, can be composted and converted to manure. The manure can be used for nourishing your kitchen garden or exotic plants on your terrace. Remember, the solar canopy protects the plants from direct sunshine and the compost and the grey water provide the necessary nourishment. Using this technique, I have over 150 pots on my rooftop.
All these are achievable in a 30 x 40 site. The net impact has been no problems during the lockdown, no energy outage, no water scarcity, you can even grow your own food.
The pandemic has made us reevaluate many aspects of life that we had taken for granted. Being at home 24X7 for over 18 months has suddenly opened our eyes to the true meaning of the term ‘Home Sweet Home’. Many people have redecorated their homes, sprouted green fingers and pursued their hobbies enthusiastically as they can devote time to being at home.
My interest was building a sustainable home. And this idea of a sustainable home was put to test during the pandemic induced lockdown.
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- 12 years after Bengaluru’s water board made RWH a rule, how are we doing in harvesting rainwater?
- Rainwater harvesting: Apartment’s water bill goes from over a lakh to zero in monsoons
- What the Jal Jeevan Mission must focus on to fix urban water supply