A mandatory labelling scheme for environmentally friendly buildings would be better than drafting new laws requiring 'green' features in new projects, developers' representatives said yesterday. But a tree expert said legislation would be more effective and urged the government to assist developers who were asked to green their sites. Their comments came after it was disclosed that a study commissioned by the Buildings Department would call for the government to scrap a policy that rewards developers with extra gross floor area for green features - ranging from sky gardens and balconies to mail boxes. Instead, the consultants' report says the administration should follow the examples of Japan and the mainland, compelling developers to provide such green features by law. Sources close to the department said the study also suggested setting up a more recognisable and thorough labelling scheme for green buildings, as an alternative in case developers strongly oppose new laws. The current green buildings labelling scheme - the Hong Kong Building Environmental Assessment Method, or HK-Beam - mainly assesses a building's indoor environmental performance, but not its impact on air flow. David Yau Kai-cheung, an executive committee member of the HK-Beam Society representing Henderson Land Development, said: 'Legislation for green features might not be the best solution overall, as it introduces more red tape.' Developers needed a clearer policy from the government to encourage green and sustainable buildings, he said. Jim Chi-yung, a tree expert and chair professor at the University of Hong Kong, favours legislation. He said a study by the Ontario government in Canada showed an increase of 7 per cent in rooftop greening areas could reduce the daytime temperature in Toronto by 2 degrees Celsius. He said the Hong Kong government should provide technical assistance for developers exploring vertical greening and rooftop greening.