Back home, the municipal corporation has big plans for the city, but most of these are on paper. Developers, too, haven't warmed up to the idea, essentially because of the cost factor.The Brihanmumbai Municipal Corporation (BMC) proposes to award ratings to residential buildings which have eco-friendly fittings. For every eco-friendly feature that a building incorporates, it is given one star. The important features under consideration are rainwater harvesting, solar panels, sewage treatment plants, among others. The builder can then use this rating for tax rebates.

A BMC official, however, said the plan hadn't got off the ground. "We have proposed, for instance, that for every star that a builder is awarded, they get a 10% rebate. However, the approval for it is still pending for the past year."

Builders, the official said, could avail of the rating without fringe benefits. However, despite the BMC's ad campaigns, no one has come forward. A well-known city builder said, on condition of anonymity, that the concept would gain more acceptance among commercial builders than residential. Also, the BMC proposal restricts the benefits to areas within its jurisdiction.

While government officials feel the IGBC target is modest, real estate developers insist that the high cost of constructing green buildings is a deterrent. They feel the cost of raw materials for a green building is very high, in turn increasing the overall investment cost by up to 7%. Energy-efficient products like solar panels, wiring equipment are often imported, as the country has just a handful of manufacturers.

However, according to Bureau of Energy Efficiency director general Ajay Mathur, within two years, energy-efficient products that are imported would be relatively cheaper. "Solar fittings will not gain acceptance unless the cost comes down. This is possible only if more companies invest in R&D and manufacturing of photovoltaic cells which are used in solar panels," says Milestone Capital Advisors MD Ved Prakash Arya.

Other builders feel that green buildings are feasible only for residential townships as a whole than individual buildings, to bring costs down. "The concept has caught on amongst commercial buildings because corporates and MNCs insist on green buildings. Residential buildings haven't caught on yet. We should not only promote "green" as an efficiency, but also as a happiness factor. This will reach out to residents," says Shree Ram Urban Infrastructure VC and CEO Vikas Kasliwal.

Mr Mathur says power ratings per square feet should be made available, in order to make green buildings more lucrative to builders and customers. "One should have ratings for power that will tell a person how much energy will be consumed per square feet and at what cost. This will attract people to green buildings."

Real estate funds, however, see it as a good financial proposition. "Either green buildings have to be made mandatory or energy and water constraints will force people to make this investment. In the future, green buildings will see a large premium," says Mr Arya of Milestone Capital Advisors, which recently entered into a joint venture with UK-based Ecofirst, a developer of sustainable buildings.

Builders like the Hiranandani Group have taken already taken to green buildings. "We have won over 10 awards for our gardens and landscaping. Our Powai township has the largest sewage recycling plant in the city, which can treat 2.2 million litres per day. We have also planted three lakh trees and all of this has been out of our interest," said MD Niranjan Hiranandani.

A few builders say that to reach the 1 billion sq ft footprint, existing buildings should be made energy efficient by changing the electrical fittings and recycling water. "I fear we might not achieve the 1 billion target. We should convert old buildings into green buildings to achieve this target," said director (general works) Central Public Works Department Anil Kumar.

However, there are a few who feel all that's needed is a change in mindset. "Change of perception is needed in the minds of developers. It is not expensive. The cost of materials has come down considerably in the past four years," said IGBC chairman (Delhi chapter) Vidur Bhardwaj.