Types of window glass

Plate glass is widely used in the building of homes and offices. Sometimes called as float glass or rolled glass, it is usually made from silica with additives such as lime and the oxides of magnesium and aluminium added to lower the melting point and to improve strength. Often called soda-lime glass, it accounts for around 75% of all glass production. The Pilkington brothers in the UK introduced the 'float glass' method of production which floated the molten glass on a bed of molten tin to output good quality sheets of plate glass, free from distortion. Cheap, transparent, colourless and available in large, thin sheets, float glass or plate glass has become the standard basic material for architectural and building work. Thicker sheet glass tends to become light green in colour.

Tinted glass is made by adding coloured pigments during the manufacturing process. It can be used for design or aesthetic reasons but, as more colour is added, it reduces light. Standard colours for tinted glass are grey, blue and bronze and may be used on roof skylights, vehicles or screen panels. Strong tints or the thick glass not only cut the amount of light transmitted, but they also increase the heat absorption so tinted glass panels can become very hot and may need to be toughed if panes are not to get overstressed and break.

One of the main disadvantages of sheet glass is its brittleness. Glass is hard but is easily fractured and, when broken, splits into many sharp fragments. Laminated glass was developed to counteract this and offer a more robust material that has all the properties of normal glass but is much harder to break. Laminated glass also has the benefit of not breaking up into small shards. It is made by fusing two panes of glass bonded around an inner layer of a polyvinyl compound. Laminated glass, sometimes called 'safety glass', not only offers greater durability it can also reduce noise and give higher thermal protection. It is often used for shop windows, secure buildings as it stays intact even when broken.

Toughened glass is often mistaken for laminated glass but there are important differences between the two. It is not just differences in manufacture that separates them, they have distinctive properties that make tithe more or less suitable for various applications. Toughened glass, sometimes called tempered glass, is a high strength material made by heating glass to a very high temperature then rapidly cooling it. The rapid cooling compresses the glass surface to create a strong outer layer that makes tempered glass up to five times stronger than normal glass. Toughened glass is used in products that require both strength and resistance to heat such as shower cubicles, splashbacks and protector screens.

As more glass is used in buildings they developed problems with dissipating the heat produced by strong sunshine. Also called solar control glass, reflective glass can be clear or tinted and has a thin layer of metal oxide applied to the surface. Available in an array of tints, it reduces the solar heat while allowing most of the visible light to pass through unimpeded. Solar glass units are usually double glazed so they have good insulation against heat and noise. In sunny weather, it reduces the heat gain in a room and in cloudy weather it allows the maximum level of natural light.

This type of glass is a high tech product that allows light to pass through but reflects heat, so indoor spaces stay light but remain temperate in any weather conditions. The low-E stands for 'low emissivity' and combine high heat insulation with relatively high visibility. Thus letting light through but not heat. Low-E glass has a transparent metallic coating that reflects longer wavelength heat-carrying light without impeding short-wavelength natural light. It works in both directions, reflecting heat back into the room on cool, winter nights. The drawbacks are a slight green/blue tint and a lack of durability. As coatings are very thin they can be easily scratched during window installation or deteriorate over time. They are also more expensive than other glass windows.

This type of glass is textured or patterned after manufacture using a variety of etching or sandblasting techniques. Designs can also be 'imprinted' into heated glass using patterned rollers or etched into the glass with acidic chemicals. Frosted glass panels admit plenty of natural light but obscure the view by limiting the transparency. They are frequently used on bathroom windows or area that require both light and privacy. The decorative patterns are useful for special features such as glass door panels or statement windows.

This is not really a type of glass as pretty much any glass can be used in panels that are double glazed or triple glazed. Panes of glass are sandwiched in layers with spaces between filled with an inert gas such as argon. Panels sometimes include a desiccant to prevent condensation forming between the panes. Double and triple glazed units are thermally efficient and form a noise barrier.