Page 79 - Hong Kong Green School Guide

3. Green School Guide - 3.3 Energy Saving
Hong Kong Green Building Council 77
3.3.2 Double Glazing
Benefits
• Reduce heat gain through windows, hence lower energy requirements for air
conditioning (estimated annual energy saving is 130 kWh/m2 of air conditioned
area for the difference between double glazing and single glazing. This is
equivalent to a 25-Watt light bulb for 5,200 hours’ operation);
• Improve thermal comfort near the window area; and
• Improve acoustic insulation and therefore reducing noise transmission from
outdoors.
Issues to Consider
a. Opportunities
• Schools can adopt double glazing for new developments or replace existing
windows with double glazing;
• Compared with single glazing, double glazing:
- - offer more thermal insulation;
- - offer better insulation from outdoor noise;
- - reduce internal condensation; and
- - are more expensive.
b. Constraints
• For retrofits, window frames fixed on wall openings might also need to be
replaced as double glazing are thicker.
c. Solutions
• Colour coating and/or low-e coating can reflect radiant heat;
• Useful References (1) & (2) provide details of double glazing and coating
type (colour or low-e);
• For retrofitting existing window frames, the following should be noted:
- - Scaffolding may be required;
- - Window frames must be securely and rigidly fixed to window opening on
walls;
- - Waterproofing between window frame and window opening required;
- - Water seal required at window frames;
- - Useful Reference (3) provides further details regarding window frame
replacement; and
- - Consult RegisteredGeneral Building Contractor to evaluate the practicality.
Applies to NS & ES