Float Glass

This is the correct term for normal glass. Where old-fashioned plate glass was manufactured by rolling it out and polishing it, float glass is produced by floating molten glass on liquid tin which produces a flat surface with no imperfections.

• Float glass is usually made in thickness of 3mm to 6mm (⅛in to ¼in).

Low-e glass

This glass allows heat from sunlight to pass into a room but prevents heat then being lost in the opposite direction. This is due to an invisibly thin layer of metallic film on the inner pane of glass which only allows certain wavelengths of UV rays to pass through, while still allowing all the light to flood in.

Toughened Glass

Or tempered glass, is normal glass that has been baked to become about five times stronger than float glass. This means it cannot be cut; any shaping, trimming or fixing holes must therefore be cut into the glass before it is hardened.

Instead of breaking into dangerous shards, toughened glass shatters into less dangerous small, blunt lumps.

• Toughened glass may be used as safety glass if it meets British Standard 6206.

Laminated Glass

Is made of a bonded sandwich of tear-resistant, clear plastic film surrounded by two layers of normal float glass. If impacted, the window will break but the film in the middle prevents it from collapsing, and can therefore provide stronger security to your home.

This glass also prevents sunlight from bleaching carpet and upholstery.

• Laminated glass is most commonly available 6.5mm (¼in) thick.

• Laminated glass may be used as safety glass if it meets British Standard 6206.

Fire-Resistant Glass

Made as laminated glass, or with steel wire mesh embedded, this glass might crack, but will not collapse and can therefore prevent the spread of smoke and flames.

• To meet this classification the glass must be certified as FRG30 and meet British Standard 476.

Self-cleaning Glass

This does not permanently remove the need for window cleaning, but will significantly reduce the frequency that the job must be done. Self-cleaning glass is coated with a thin transparent layer of titanium dioxide.

First, this layer works as a ‘photocatalyst’ using UV rays in daylight to break down organic dirt such as tree sap and bird droppings. Then, because this layer is also water loving, or ‘hydrophilic’, rain water is spread evenly over the glass instead of forming droplets, and runs off in a sheet that takes all the loosened dirt with it.

Obscured Glass

Is particularly useful in a bathroom as it allows light to penetrate without permitting your neighbours to see more than they bargained for when you step out of the shower!

Obscured glass comes in variety of forms using colours, patterns, textures and translucence to distort a clear view through the window.

It's also possible to purchase self-adhesive window films that can be applied to a window to give it a frosted and/or patterned appearance.

Solar-Control Glass

Is coated with a tinted, reflective film that controls the amount of heat gained from the sun. In reducing the amount of glare, these windows also reduce the level of illumination.

Electrochromic Glass

This includes a layer of tungsten oxide that changes colour when an electric current is passed through it. This kind of glass must therefore be wired up to an electricity supply so that you can choose the amount of light that is allowed to permeate the window, from completely transparent to totally opaque.

• This glass can therefore be used to shade out sunlight or ensure privacy.

Argon-filled Glazing

This is not strictly a type of glass. Argon is a natural, colourless, inert, non-toxic gas which improves the thermal efficiency of a window when it fills the air gap in between the double glazing. An even greater improvement can be achieved using the similar, but more expensive, krypton gas.

Divided & Simulated Lights

Where a large window is divided into smaller ‘lights’, this can be done in two ways. The most expensive method uses truly separate, individual panes of glass, each of which is held in its own frame.

• The advantage here is that a small pane can be replaced in the event of a breakage.

The cheaper approach uses one large pane of glass on to which imitation glazing bars are adhered.

Further information and useful links

• Types of window
• Window frame materials
• Common sizes of window
• Window requirements of the building regulations
• Making sense of the energy efficiency ratings for your home
• Full list of windows & doors topics

• Find a Double Glazing supplier near you
• Find a Glazier near you