Page 77 - Hong Kong Green School Guide

3. Green School Guide - 3.3 Energy Saving
Hong Kong Green Building Council 75
3.3.1 Window Films Applies to NS & ES
Benefits
• Reduce heat gain through window, hence energy requirements for air
conditioning; and
• Improve thermal comfort near the window area.
Issues to Consider
a. Opportunities
• Schools can install window film to reduce heat transferred through the
window.
b. Constraints
• Life expectancy of window film;
• Direction the window faces (windows facing directions other than south-west
and south-east will have limited solar radiation reduction, therefore it may not
be cost-effective to implement films);
• Installation technique; and
• Maintenance commitment.
c. Solutions
• Three major types of window film: tinted film, reflective solar film and Low-E
(Low Emissivity) film;
• Tinted film is less expensive than solar reflective and Low-E film, but may
block a large portion of visible light (hence creating a darker room), which
increases the demand for artificial lighting. Tinted film may also create glare
for neighbours;
• Reflective solar film is more expensive than tinted film but reflects more solar
radiation and reduces heat gain. However, it can create glare for neighbours;
• Low-E film is more expensive than tinted and reflective solar film. However, it
allows more visible light to pass through windows, lessening the demand for
artificial lighting. It also has less impact on the transparency of the window
and glare is not an issue;
• In order to increase the longevity of the window film, professional installation
(inclusive of with a warranty) is recommended; and
• Proper maintainence to preserve the film from scratches during cleaning.