Page 50 - Hong Kong Green School Guide

3. Green School Guide - 3.1 Green School Sites
Hong Kong Green School Guide 48
3.1.6 Green Roof Applies to NS & ES
Benefits
• Enhance biodiversity;
• Pleasant learning environment for students;
• Reduce heat going to floor below hence
reduced energy needs for air conditioning
(estimated annual energy saving is 3 kWh/
m2 of roofed air conditioned area which is
equivalent to a 25-Watt light bulb operating
for 120 hours);
• Reduce heat island effect, i.e. reduce the local ambient temperatures and
therefore reduce discomfort;
• Filter dust pollutants and improve local air quality;
• Visual enjoyment; and
• Reduce surface runoff to drainage system hence improve storm water
management and improve ground water recharge.
Issues to Consider
a. Opportunities
• Shrubs including flowering shrubs, ground cover and grass can be planted
on the roofs of campuses.
b. Constraints
• Limited roof space;
• Long hours of shading due to surrounding buildings;
• To determine the feasibility of installing green roofs, the following critical factors
that would affect the structural loading should be considered: saturated soil
weight, green roof types, vegetation types, roof usage in respect of amount
and rate of visit, additional load due to growth of trees, etc.;
• Water proofing & potential water seepage issue;
• Additional water supply point, insufficient water pressure to roof for irrigation,
and drainage provision for planted areas;
• Compliance to The Provision of Means of Escape in Case of Fire, such as
restricted number of persons on roof, roof designated as refuge floor thereof
not to be obstructed by green roof construction;
• Frequent irrigation can be labour intensive;
• Additional access and safety devices, such as balustrade, railing, barrier-
free access provisions, etc.;