COPENHAGEN: 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.