Booming cities with rising skylines are hallmarks of China's development over the past 30 years.

Urban Chinese on a per capita basis have seen their housing space almost tripled from 8.59 square meters in 1985 to 23 square meters last year.

But several of the developers who have prospered from the housing booms now have second thoughts the way they have made money. In a way, they feel they have "sinned" because they fear the construction industry has had its share of guilt in contributing to high energy and natural resource consumption, high waste and greenhouse gas emissions.

And they say they must act to make up for what they have erred by going green.

"We understand that the scale and volume of modern economic activity has brought humanity to a historically critical moment," some 200 businesspeople from their four non-government organizations announced in a declaration made public in Copenhagen yesterday.

They didn't shy away from the harm the construction business has done on the nature, and its responsibility for global warming.

Expanding housing space alone increases urban people's consumption in electricity, Zhang Zaidong, chairman of the Beijing-based real estate company, Tiptop International, said at the Chinese Businesses Responding to Climate Change forum, on the sideline of the UN Climate Change Conference.

To satisfy the insatiable electricity demand, power plants have been built and most of them rely heavily on fossil fuels, he said.

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The use of wood in construction alone has been responsible for the loss of a lot of forests not only in China but also around the world as China is the largest timber importer in the world, Wang Shi, Chairman of China Vanke Inc, said.

By Wang's calculation, 70 percent of the imported wood has gone to construction, and 70 percent of the wood used in the construction business has gone to residential buildings.

To Feng Lun, chairman of the Vantone Group, the future could be bleak for China's urbanization process as there is very little land available for housing development.

China simply cannot afford to cut more trees if it continues the Western path of urbanization and construction, he said. If the best urban center has at least 60 percent of its land covered by trees, then China only has 6 percent of land area for cities' growth.

The proposed ways to go green in construction business vary from one businessman to another, even though they all agree to "initiate a process of harmonization" between nature and man and "create a green model for economic development".

Zhang Zaidong has built a group of residential houses in Nanjing, which is devoted to low-CO2 emissions and renewable energy use. He installed thin tubes in the walls and link the flow of the water to a geothermal system that circulates through a buried loop system in the ground several meters below the Earth's surface.

The system makes the use of the constant temperatures under the ground, cooling off the excessive heat in the apartments in summer and warm the rooms in winter.

Meanwhile, he also has solar panels to generate enough electricity in summer and power the water circulation.

This way, the households no longer use air-conditioning in this city - which can seem like an oven in summer - and save about 80 percent of the electricity bills.

"We should stop building power plants," he said. "Instead, we should use the money to encourage the use of renewable energy."

The government must also clear the hurdles it has erected to prevent electricity generated by households using renewable energy from entering the power grid.

"If we do that and clear the barriers, we'll be able to cut CO2 emissions by 27 percent within the industry by the year 2020 in construction industry," Zhang said.

Wang Shi, meanwhile, said that his technical team has devised ways to replace wood molds with steel molds in the building of houses. Wood panels used in construction are usually recycled only 6.5 times, while the steel could be reused 400 times.

By using steel instead of wood alone, construction alone could not only help save 9,000 hectares of forest, but also the amount of electricity and water used to process wood panels, Wang Shi said.