Single glazing is a single layer of glass and isn't effective in reducing the transfer of heat, light, sound, or U.V. It is not often used in external situations as there are more effective options.
Glass
Single glazing
Double glazing
Laminated
Low-E
Obscure
Tinted
Double glazing or an insulated glazing unit is made of two layers of glass with a sealed air space between. Performance can be optimised by selecting the correct spacer gap and types of glass.
Laminated glass is a type of safety glass with two panes held together by a clear vinyl interlayer. Laminated glass is often used for sound reduction and to reduce fading. It is also one of the most effective types of safety glass for security purposes.
Low-E glass has a coating which improves its thermal efficiency. The coating is virtually invisible but will have a positive impact on the heat transfer through the glass.
Obscure glass is used for privacy as it restricts visibility through a window. It is commonly used in areas like bathrooms.
Tinted glass can be used to reduce the glare and fading from the sun or as an aesthetic feature. Grey tinted glass is common in New Zealand homes.
Glass tint colours
In summer, Low-E glass reflects the sun’s heat is back outside, reducing internal heat gain.
During winter, Low-E glass reflects heat back into the room, so less heat is lost through the windows.
Double glazing
Low-E plus
Low-E EnergySaver™
Low-E max (inc Argon gas)
Low-E Xcel (inc Argon gas)
Low-E Xtreme (inc Argon or Krypton gas)
Low- E Lightbridge™ (inc Argon Gas)
Low-E Performatech™ (inc Argon Gas)
Energy efficiency (low > high)
WEERS rating Thermal performance using standard aluminium frame. Rating out of 6.
Lower power bills
Low-E glass has a coating which reflects the heat back from its source, either from the inside or the out and reduces the amount of energy you need to heat or cool a building internally, providing energy savings over the course of a year.
Reduced condensation
Low-E double glazing increases the internal glass surface temperature, which reduces the likelihood of condensation on the inner glass surface. Condensation is also relative to the humidity inside an area, sometimes a dehumidifier helps to reduce the humidity.
Warmer healthier home
Low-E glass reflects heat back into a room, so less heat is lost through the window. The resulting reduced condensation on the inner glass surface means your home stays drier, which in turn makes for a more healthy living environment.
Improved insulation
Low-E glass reduces heat loss and solar gain, reducing heating needs in winter and cooling requirements in summer. Better insulation makes it easier to keep temperatures constant, so the internal comfort level is increased.
Reduced fading
Low-E double glazed windows can help protect furnishings in the home from fading by reducing levels of UV light from the sun.
Sound
UV / Fading
Heat gain
Light and glare
Heat loss and condensation
Safety and security
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Sound
With compact housing and traffic or industrial noise, sound reduction is an important factor when choosing glass. There are a range of glass types that will reduce sound, but it does depend on the frequency and pitch of the sound as to what type of glass is most effective.
A double glazed unit has significantly better acoustic performance compared to single glazing, however, laminated glass is the most effective option.
*PSR - Perceived sound reduction % in comparison to 3mm clear float glass. Percentages vary depending on glass combinations.
UV / Fading
UV damage or fading to furnishings is something that is often thought about when selecting glass. You can reduce fading by selecting glass that reduces the UV transmission through the window.
Tinted glass is an effective option for reducing fading as the interlayer absorbs the UV light. To further reduce fading we suggest combining tinted glass with laminated glass. Reflective glass is the best to reduce fading.
*FRC = Fading reduction coefficient compared to 3mm clear float glass. Performance depends on glass combinations.
Heat gain
Heat gain from the sun is a common challenge in New Zealand homes. Double glazing can help regulate inside temperatures by reducing the heat transfer from outside.
Tinted and Low-E glass will further reduce the heat gain as they absorb solar energy.
Reflective glass is the best option to reduce solar heat gain, but it is not commonly used in homes.
*Reduced solar heat gain in comparison with clear on clear double glazing. Percentages vary depending on glass combinations.
Light and glare
The glare from the sun can be frustrating in areas exposed to the sun. Glare can be minimised by choosing glass that reduces the light transmission.
Low-E coating helps to reduce light transmission, and tinted glass will further reduce the glare. Reflective glass is the best to reduce light and glare, but it is not commonly used in homes.
*VLT% is the approximate visible light transmission. Percentages vary depending on glass combinations. Clear on clear double glazing has a VLT of approximately 80%.
Heat loss and condensation
A standard double glazed unit will effectively reduce heat loss and condensation in comparison to a single glazed window.
To further enhance the insulation, we recommend combining double glazing with Low-E and Argon gas as the best solution. This gives a heat loss reduction of up to 70% compared to 4mm clear single glazing as it keeps the inner pane of glass warmer. Thermal spacers can further enhance performance and help reduce condensation.
Note: Double glazing does not eliminate condensation.
*Improved heat loss reduction in comparison with 4mm clear float glass. Percentages vary depending on glass combinations.
Safety and security
Safety is important and the NZ Building Code stipulates that certain sizes or locations must be able to withstand impact without breaking.
Standard safety glass will shatter rather than break. However, there are special glass types with varying penetration resistance through to bullet-resistant glass.
All UNO windows and doors comply with the NZ Building Code. For standard safety requirements, toughened or laminated glass is sufficient. Glass designed for forced entry protection is usually only selected when high security is required.
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