How much do you pay for your electricity bills? Let's assume an average of Rs 5,000 every month. What if you could cut it down by half? Over the life cycle of your building (50 years), the savings invested in a systematic investment plan  at 12 per cent amounts to Rs 9.86 crore, if other factors remain constant. Not a bad investment.

This is just one of the reasons to build an eco-friendly house or convert your existing house into an eco-friendly one. We have built our case based on the experiences of Arna Seal, a 42-year-old consultant sociologist who lives in Kolkata.

What's an eco-friendly house?

For Tata Energy Research Institute (Teri), an eco-friendly home is one that "depletes the natural resources to the minimum during construction and operation". Happily, it also depletes your income the least.

Why go green?

The reasons are many, the benefits both tangible and intangible.

Cost cutting: "Let us talk money. Incidentally it is also green, is the approach that goes down best with clients," says architect Karan Grover, who has designed in Hyderabad the first Platinum (highest) rated building outside the US under the Leadership in Energy and Environmental Design Green Building Rating System.

While construction material works out to be cheaper, installation of certain equipment cost more initially, but are worth it. According to CII-Sohrabji Godrej [Get Quote] Green Business Center, which promotes green businesses in India, the incremental costs can be recovered in 2-3 years. "After you recover the costs, it translates into savings," says Harsha Sridhar, chief anchor (design and architecture), Biodiversity Conservation, an enterprise that provides green solutions for urban living.

Healthy and wise: Eco-friendly houses are good for the environment, and also for the people staying within as they improve the quality of air inside the house.

Environment-friendly: If you are worried about Arctic glaciers melting and blame it all on industries and thermal power stations, think again. With a house that is eco-friendly, you can ensure that the next generation has that much of more oxygen to breathe and that much of more greenery to feast their eyes on.

Having been part of the development sector for over a decade, Seal was always interested in alternate technologies. She got in touch with Bangalore-based green architect Chitra Vishwanath, who agreed to help. Since then Richa Bose, a Kolkata-based architect, has been her companion in the green endeavour.

How to make a start

While the things related to construction and design can be implemented only when a house is being built from scratch, most can be effected even in an existing house. For those who live in an apartment, it has to be a community initiative.

Energy efficiency

Reduce need for lighting: The house needs to be designed in such a way that it receives ambient lighting and does not require artificial lights during the day. The working areas of Seal's house face the south and receive sufficient light. Use energy efficient lamps and appliances.

Try replacing incandescent light by CFL lamps. Light Emitting Diode (LED) lamps are even more energy-efficient. While an incandescent bulb costs Rs 12, a CFL costs Rs 120. However, it works out cheaper because it saves energy and lasts longer. LED lamps, too, are expensive initially. Six LED lamps plus a solar panel cost Rs 5,000.

"When buying any electronic equipment, check the Bureau of Energy Efficiency (BEE) ratings," says Mili Mazumdar, associate director, Sustainable Building Science, Teri-Griha, Teri's green building arm. A list of products and their ratings can be found at www.bee-india.nic.in/.

Minimise cooling and heating costs: "Give the west facing windows ample sunshade so that the room stays cool at night," says Jaigopal G. Rao, managing partner and director (designs), Inspiration, a team of eco-friendly builders. An extra layer of ceiling or high albedo (that have a high light reflecting quotient) roofs also helps. The roof in Seal's house is partly covered with glazed tiles that reflect light and block heat transmission inside. There is a layer of earthenware below the ceiling for insulation. The bricks in the walls are arranged in a rat-trap bond (invented by famous green architect Laurie Baker).

Says Vishwanath, "In humid places, cross ventilation is important." That was kept in mind while designing Seal's house. Explains Bose: "Wind from the south enters through the entrance on the ground floor, makes its way up through an open courtyard in the center and passes out through vents in the north. This airflow keeps the house cool and airy." She says there is no need for air-conditioning except during the hottest days in summer. A solar thermal heating system on her roof preheats the water to a standard temperature so the geysers need lesser time and energy.

Water efficiency

All of the following can help you cut down on water usage by 40 per cent.

Water-saving equipment: "Water savings fixtures, low-flow showers, double flushing cisterns can save water," says Mazumdar.

Rainwater harvesting: In areas with scarcity of water during summers, such as Chennai, you can actually harvest rainwater," says Rao. The stored rainwater is soft, arsenic free and can be used for drinking purposes by using a normal candle purifier. Seal has a system in place to use rainwater. "Allowing the rainwater to percolate into the ground can also help gradually increase the water table in the area," says G. Shankar, founder and chief architect, Habitat Technology Group, an NGO working in the building sector.

Recycling: Water used for washing and showers can be reused for flushing.

Materials and resources

Going local: Seal wanted to use compr-essed earth blocks for the walls. However, the soil in Kolkata is different. Transporting the blocks from Bolpur, which has the required soil, was turning out to be expensive. So, she decided to capitalise on local material and settled for bricks instead.

Building material: Use steel and concrete minimally; they consume a lot of energy when being produced. Go for alternate building materials like flyash bricks, ferro-cement (built with using minimum cement around a wire mesh) and compressed earth blocks.

Steel has not been used for pillars in Seal's house as the rat-trap bond wall supports the building. It also reduces use of mortar by 25 per cent. Wherever possible, ferro-cement has been used for doors, walls and roofs. Locally made earthen pots have been used as filler slabs (alternative material used to replace concrete in the lower bottom half of roofs that does not take in tension).

All these also brought down construction costs. While ferro-cement channels work out to be 17 per cent cheaper than regular RCC slabs, filler slabs with Mangalore tiles cost 11 per cent lesser. Using the rat trap bond technique is cheaper by 14 per cent than conventional bricks, while compressed earth blocks are 28 per cent cheaper.

Recycling: "Recycle as much as possible," advises Sridhar. Seal procured the bulk of the wood she has used in doors from an old building site.

Environmental quality

Ventilation and greenery: Proper ventilation maintains the air quality with optimum oxygen quantity. Plants keep the house cool, protect it from dust and noise and ensure a healthy environment.

Non-toxic paints: "Use water-based paints that do not spew harmful volatile organic compounds," says Sridhar.

Check the green claim

Many developers nowadays are blatantly using the green bait to lure customers. "Before investing, you should check such claims, the builder's reputation and clarify who will handle the project," says Prodipto Sen, vice-president (marketing), Alpha G: Corp Development, a real estate firm.

Hurdles on the green path

Eco-friendly housing has not caught up in India for many reasons. With rising land prices, very few people can actually afford buying a plot of land and constructing a house. Says Grover, "The market for eco-friendly homes is still young. It appeals mainly to businessmen who can save money by implementing eco-friendly measures in office buildings." Vishwanath attributes it to lack of awareness.

For Seal, it was an enriching experience. "It has improved the quality of light and life in my house," she sums up.