Allocate 30pc of area to plants: report Thirty per cent of all development sites should be covered with greenery to help reduce the city's soaring temperatures, according to a consultancy study commissioned by the Buildings Department. The study also recommends that a much-criticised policy which rewards developers with extra gross floor area for adding so-called green features to their projects be scrapped and that the developers be required by law to provide such features. The consultancy was commissioned amid a storm of criticism after a government audit report disclosed that the green feature policy - aimed at making projects more environmentally friendly - had provided a loophole for developers to increase the density of their projects. It comes as intense public pressure against massive developments with wall-like towers that block air flow appears to be yielding results, with the Kowloon-Canton Railway Corporation trimming the density of development along its West Rail line. A source close to the department said the study - which reviews building design in relation to the city's urban environment, looking at such things as air flow and green features - was reaching the final stage and professionals' views would be sought in October after it was completed. Recommending that 30 per cent of development sites be devoted to greenery, the researchers note that past studies had shown that a 10 per cent increase in green coverage could reduce average city temperatures by one degree. In some places such as Japan and the mainland, 30 per cent green coverage was required by law, the source said. The study found that existing sky gardens and podium gardens - green features for which developers receive floor area credit - are not as effective as they should be in increasing air flow and diluting pollutants from the surrounding area. It criticises developers for placing sky gardens too high in buildings or on fire escape or 'refuge' floors that are too cramped and do not allow space for vegetation growth. And podium gardens often contain large club houses, which block the flow of air. Since 2001, developers who add environmentally friendly features - ranging from balconies, to bigger mailboxes - are awarded bonuses of up to 8 per cent of the total permitted gross floor area. But in 2005, the Audit Commission criticised the bonus scheme for increasing the density of developments, which could add to the 'canyon effect' at pedestrian level. An investigation by the South China Morning Post later revealed that several developments, including Henderson Land's massive Grand Promenade at Sai Wan Ho, had added floor space worth hundreds of millions of dollars under the scheme - at little cost in land premiums. The Council for Sustainable Development urged the government to review the effectiveness of measures promoting sustainable building design. Secretary for the former Housing, Planning and Lands Bureau, Michael Suen Ming-yeung, promised a review of the policy last year. 'Giving incentives such as gross floor area is controversial and the practice is fading out globally,' the source said. The study recommends requiring sky gardens to be created at lower levels and podium gardens not to be blocked with structures. It also recommends relaxing the limits on the ceiling height of sky gardens and on the size and number of balconies. 'Some balconies are so small they lose the function of shading sunlight and reducing noise pollution,' the source said. If developers strongly opposed the introduction of new laws, the study proposes setting up a comprehensive labelling scheme for green buildings as an alternative.