WINDOW AND GLASS PERFORMANCE
We should always consider the window frame and glass as a total unit when assessing performance. Also the actual fitting of the window unit into your dwelling is critical. Gaps and spaces around the window frame will adversely effect window performance.
Below are some issues that clients raise and are worth considering.
GRADING GLASS TYPES
In an attempt to rate the performance of glass usage we have listed below glazing methods from basic to most effective.
| Low Performance | Clear Glass |
| | | Tinted glass |
| | | Coated glass (usually termed ‘Low E’ glass) |
| | | Coated, laminated glass |
| Highest Performance | Coated laminated glass in double glazing |
This is a very simple assessment of glass effectiveness but may assist in selection. Other factors such as geographic location, direction faced (N, S, E or W) and shading will also influence performance.
THERMAL INSULATION
All materials lose heat, but some more quickly than others. The rate of heat loss depends on the surface emissivity of the material. Emissivity is defined as the rate of emitting (radiating) absorbed energy. the lower the surface emissivity, the better the glass reduces heat gain or heat loss.
Ordinary clear glass has a surface emissivity of 0.84, meaning 84% of the absorbed heat is emitted from the surface.
When ‘Low E’ coatings are applied to the glass, the surface emissivity is reduced to less than 0.20. So the heat gain or loss is much lower in Low E glass than in ordinary glass.
SAFETY GLASS
- Laminated Safety Glass – Remains intact. Use where there is a risk of human impact. Grade A designation.
- Toughened Safety Glass – Breaks into small harmless particles. Use in situations requiring strength and resistance to temperature fluctuations. Grade A designation.
SOUND REDUCTION
- Thicker Glass – Generally the thicker the glass the better sound insulation.
- Laminated Glass – The interlayer assists to give higher sound insulation than normal float glass.
- Double Glazing – Best results for sound insulation are gained by using glass panes of different thicknesses or having laminated glass as one or both of the glass panes.
Note 1: Where double glazing is not feasible, the most cost-effective method of reducing sound is by using a thicker glass or installing laminated glass.
Note 2: Areas around windows. There should be no air gaps or cracks around the windows frame. A gap of no more than 1% of the total window area will result in a 10db loss in sound insulation.
AUSTRALIAN STANDARDS
All windows supplied by WINDOWS 1 comply with current, relevant Australian standards.