Varieties of window glass

Window glass comes in many forms

When replacing windows or doors, people can often overlook the various types of glass used in product construction.
Choosing the right kind of glass for your project can be crucial to getting the most out of the selection available. It is not simply a matter of choosing which type of glass is the cheapest. Today, there are so many types of glass on offer that it can be tricky to make the right decision.
The question of the insulating properties of different glass types is at the forefront, as this can be a significant factor when it comes to heating bills.
Some glass treatments let light in and keep heat out. Other types of glass protect against harmful ultraviolet rays. Some types of glass offer greater security, while others help keep out noise.
It is a matter of weighing up all the options and balancing the benefits and the costs. Here we explain the various types of glass to help you make the right decision.

Plate glass

Plate glass is widely used in homes and offices. Sometimes called float glass or rolled glass, it is usually made from silica with additives such as lime, magnesium and aluminium oxides. Aluminium is added to lower the melting point and improve strength. Often called a 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 that were 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.

Tinted glass

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. Intense tints or thick glass not only cut the amount of light transmitted but 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.

Laminated glass

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

Toughened glass

Toughened glass is often mistaken for laminated glass, but the two have important differences. It is not just differences in manufacture that separate 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 and 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 regular glass. Toughened glass is used in products that require both strength and resistance to heat, such as shower cubicles, splashbacks and protector screens.

Reflective glass

As more glass is used in buildings, they develop problems 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 various tints, it reduces the solar heat while allowing most visible light to pass through unimpeded. Solar glass units are usually double-glazed, providing good insulation against heat and noise. In sunny weather, it reduces the heat gain in a room; in cloudy weather, it allows the maximum level of natural light.

Low-E glass

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 combines 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.

Frosted glass

This type of glass is textured or patterned after manufacture using a variety of etching or sandblasting techniques. Designs can also be 'imprinted' into the heated glass using patterned rollers or etched 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 areas that require light and privacy. The decorative patterns are useful for special features like glass door panels or statement windows.

Insulated glass

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