Glazing Material
The type of glass will also affect the energy efficiency of the window.
- Low-Emmissivity (Low-E) Glass is coated with a special compound that reflects off 40-70% of the heat that is normally transmitted through ordinary glass, thereby reducing heat gain. Light is still allowed to pass through.
- Heat-Absorbing Glass contains tints that can absorb up to 45% of the solar heat, thereby reducing heat gain. Light is also reduced.
- Reflective Glass is covered with a film that cuts down the heat and the light passing through the glass.
- Plastic Glazing can be made of acrylic, polyester etc. They are lighter and cheaper. Their efficiency can also be controlled.
Number of Panes
Single-pane glass windows have very little insulating properties. Double or triple pane windows provide better insulation as the heat has to pass through multiple layers of air and glass. Some windows are now manufactured using an inert gas like argon in between the panes of glass. It has been found that inert gases provide better insulation than air.
Here is an excellent comparison of the energy efficiency of single-, double-, triple-pane windows and low-e windows. A must-see site.
External Shading Devices
Simple shading devices like curtains, awnings, shutters or screens can also be used to make windows more energy efficient.
The next article will focus what to look for when you go out shopping for energy-efficient windows. So see you then!!
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