Page 57 - Hong Kong Green School Guide

3. Green School Guide - 3.1 Green School Sites
Hong Kong Green Building Council 55
3.1.8 Heat Shield Roof Coating Applies to NS & ES
Benefits
• Reduce heat island effect, i.e. reduce the local ambient temperatures and
therefore reduce discomfort;
• Reduce heat going to floor below hence reduce energy requirements for
air conditioning (up to 10OC drop in room temperature or estimated annual
energy saving is 1 kWh/m2 of roofed air conditioned area, which is equivalent
to a 25-Watt light bulb operating for 40 hours);
• Highly reflective roofing diverts damaging ultraviolet rays away from the roof
assemblies hence slows the aging process of roof structure; and
• Lower roof temperatures reduces the rate of material chemical breakdown
thus significantly decreases premature roof material failure and subsequent
repair or replacement cost.
Issues to Consider
a. Opportunities
• High reflectivity materials (Heat Shield Roof Coating) can be applied to roof
that can divert a large portion of heat radiation back to the atmosphere and
hence lower air conditioning demand.
b. Constraints
• In existing schools, poor condition (e.g. uneven surface, cracks) of roofs due
to aging may be present, which hinders adequate application of coating.
c. Solutions
• For existing schools with roofs in poor condition, schools may consider
replacing the roof’s surface materials (and possibly the waterproofing layer)
before applying the roof coating;
• Please refer to Useful Reference (5) for Building Maintenance Guidebook
– Section 4.1.3 by Buildings Department of Hong Kong for more details of
replacement of roof structure;
• Heat shield roof coating comes with additional benefit of waterproofing
properties; and
• Schools can contact contractors in Useful Reference (4) for practicality.