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LCQ19 : Green roof or flat roof projects

Following is a question by the Hon Choy So-yuk and a written reply by the Secretary for the Environment, Transport and Works, Dr Sarah Liao, at the Legislative Council meeting today (June 28) :


In its progress report regarding the motion on "Conservation of Energy" passed by this Council on 14 December last year, the Environmental Protection Department points out that the Architectural Services Department has incorporated green roof or flat roof landscaping into new government building projects wherever possible since 2001, and almost 40 related projects are either being planned or under construction; moreover, the Government will continue to implement green roof or flat roof projects wherever feasible.  In this connection, will the Government inform this Council:

(a)  of the details of the 40 projects and those that involve roof greening;

(b)  among the projects which involve roof greening, of the percentage of the area of the roofs on which greening work has been carried out, in the total roof area, and the average cost per square foot for roof greening; and

(c)  of the criteria for deciding whether green roof projects will be implemented on buildings, and whether such criteria include energy conservation?


Madam President,

(a)  Government buildings projects under planning/construction that involve roof greening include schools, community centres, hospitals, office buildings, crematoriums and recreational and cultural facilities.  The extent of greening will be determined by the use and design of the roof, which usually include provision of planters, soft and hard landscaping, paving, decking and related waterproofing, irrigation and drainage system works.

(b)  Greening accounts for 10% to 80% of a building's total roof area, depending on the building services and communication facilities located on the roof.  Similarly, the unit cost of roof greening, normally ranging from $75 to $190 per square foot (excluding the cost of structural works), is determined by the design, material specifications and site conditions, etc.

(c)  Apart from enhancing the landscape and the environment of our city, attenuating the heat island effect and improving air quality, roof greening can also improve the performance and increase the life span of waterproof and insulation facilities on the roof.  Consequently, roof greening is also conducive to energy conservation.  The Architectural Services Department, therefore, aims to implement green roof projects for new government buildings under planning, wherever practicable.

End/Wednesday, June 28, 2006