What you need to know about glass composition in triple glazing

Everyone knows that windows are made by placing glass into a frame. But what is that glass made of and how does it get special properties to make it suitable for thermal insulation? Here are all the facts that you need to know about glass composition in triple glazing.

How is glass made?

Glass is made by melting sand at temperatures exceeding 1700°C, adding waste glass, soda ash and limestone to it, and then pouring the molten mass into a tin tub and allowing it to set. This floating process creates perfectly even and clear glass sheets, called soda-lime-silica glass.

Sheets of floated glass typically come in a various thicknesses, from 4mm that is used in standard residential applications, 6mm to 10mm for larger sheets for commercial use and up to 25mm for safety glass.

Glass coatings for triple glazing windows

The 3 layers of glass in a triple glazing window all have specific properties to ensure maximum efficiency of the unit.

Low Iron Glass

These glass panels are made with the same floating method, but sand or silica with a very low iron content is used. This allows an extremely clear glass to be made, without the blue or green tint of other glass products.

All of the layers in a triple glazing window are typically made with low iron glass to allow the maximum amount of light and long-wave infrared heat energy to enter the home.

Low-E Glass

The interior glass panel of a triple glazing window is covered with a clear film to create low-E or low-emissivity glass. This microscopic film is added to the glass to decrease its emissivity, or its ability to radiate energy.

By reducing the emissivity of the glass, the insulating properties of the window is increased. The coating is applied to the glass during manufacturing on the float line while the glass is still hot, thereby fusing the coating to the glass and creating a very strong bond or hard coat.

The specialized coating minimizes the amount of ultraviolet and long-wave infrared light (heat) that can pass through a window, without blocking the amount of visible light. By applying this layer to the interior panel, heat is then reflected back into the home and not escaping through the glass to the outside.

Tempered Glass

The central pane in triple glazing is made with tempered glass. This type of glass is 4 times stronger than regular glass, and instead of breaking into shards, it crumbles into small, fairly harmless pieces.

The glass panels are heated to approximately 650°C and then quickly force-cooled, causing edge and surface compressions that strengthen the panels.

Because of its strength, it not only performs as security glass, but it is also resistant to thermal stress cracking.

Self-cleaning glass

Especially suitable for hard-to-reach windows, self-cleaning glass is an option offered by some triple glazing manufacturers.

The exterior glass is covered with a thin film that has a dual action. The first step in the cleaning process is photolytic, so daylight breaks down the organic dirt on the window surface.

The second step is hydrophilic, where the rainwater creates a film on the glass instead of forming droplets, thereby washing the dirt off. The film is also formulated to dry quickly and prevent streaking.

Aside from these characteristics, you will need to look at the energy rating of the glass that you choose for your triple glazing. An A++ rating ensures that you will get the best possible performance and efficiency from your new windows.

Published on : 26th October 2016

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