The Buildings Department has modified the 'green building' incentives to allow developers to build communal sky gardens in refuge floors. The move is expected to further encourage developers to include such facilities in new projects because they will not need to build separate floors for the gardens and hence reduce costs. Sky gardens - areas between floors for use as common gardens - are among more than 20 items in the incentives package introduced last year by the department to encourage environmentally friendly buildings. Besides adding greenery, sky gardens can improve air flow between buildings. Director of Buildings Leung Chin-man said in a new practice note the department was prepared to accept the incorporation of communal sky gardens in refuge floors, subject to compliance with fire safety precautions. For example, sufficient area for refuge needs to be provided, and all garden furniture and equipment has to be made of non-combustible materials and be firmly fixed. The buildings authority might impose additional requirements, depending on individual cases, Mr Leung said. Analysts said the department's decision to incorporate sky gardens in refuge floors was a result of lobbying by developers and industry players and would cut construction costs. Other green building features include open balconies, public corridors, lift lobbies and podium gardens. These features can be exempted from the calculation of a development's gross floor area (GFA) as incentives. The cumulative GFA exemption for all green features, excluding sky and podium gardens, should not exceed 8 per cent of the total permitted GFA for a development. Developers are keen to capitalise on the building rules and apply for approval for revised plans. Swire Properties has already received approval to build four floors of sky gardens in a twin-tower, residential redevelopment on the Swire Primary School site in Quarry Bay. Pacific Century CyberWorks last month also secured approval from the Town Planning Board to include sky gardens in seven residential towers in its Cyberport project in Pokfulam.