When it comes to buying new windows, there is an endless number of options available to you.
Whether it’s the style, frame material, or even frame colour, the type of glass is often low down on the list of decisions.
However, the glass itself also comes with a range of options….
There are eight main glass types used in double glazed windows throughout the UK:
1. Annealed/float glass
Nowadays, most windows are made by floating molten glass over molten metal to give the glass a consistent thickness and a flat surface.
This is annealed glass, also known as float glass.
All of the following forms of double-glazing start out as annealed glass, made by this method.
Double glazing is made by connecting two panes of annealed glass with a pocket of heavy gas such as argon in between.
The gas is heavier than atmospheric air, and this is what gives double-glazing qualities such as strength, insulation, and even soundproofing.
COST: This form of glass is the most cost-effective and sets the standard throughout the range.
2. Tempered/toughened glass
This option stays in good condition between 5 – 10 years longer than standard annealed glass so it doesn’t need to be replaced as often, which could balance out the higher initial cost factor.
For safety, when tempered glass breaks it shatters into small pieces which reduces the chance of serious injury in comparison to standard glass which breaks into long shards. Building Regulations require tempered glass for:
- Windows which have been fitted 800mm or lower from the floor level,
- Windows which have been fitted at a distance of 300mm or less from a door, and up to 1500mm from the level of the floor,
- Glazed doors fitted up to 1500mm from the floor level.
COST: Up to 25% more expensive than standard glass.
There is a plastic interlayer in laminated glass which coasts the pane and holds the glass is place when the window is shattered, reducing risk of injury. This glass is often used in shop windows and car windscreens.
This option has the additional benefit of security against break-ins as the glass holds tightly in place when broken. This glass also protects carpets and furniture from sun bleaching.
COST: Up to 40% more expensive than standard glass.
4. Low E glass
Low E – short for ‘energy’ – glass reflects heat back into the home using a thin film of metal which coats the glass pane.
The metal film is transparent, allowing heat and light to pass through the glass.
COST: Up to 25% more expensive than standard glass, however savings made on energy bills can balance out the cost of the initial investment.
5. Self-cleaning glass
Self-cleaning glass has a thin layer of titanium dioxide on the outside – thin enough to allow a minimum of 95% light of a standard window through.
The titanium dioxide is stimulated by UV rays to extract water from the air.
These water molecules react with the titanium dioxide on the surface of the window to break down any organic matter.
The organic matter is either washed away when it rains, or when gravity causes the thin film of water molecules to run down the window, cleaning away the organic matter.
The glass inside the home still needs to be cleaned manually, and the effectiveness of self-cleaning glass is limited in areas with high pollutant levels, or significant airborne salt levels.
COST: Up to 20% more expensive than standard glass.
6. Noise control glass
This option is best for properties located in areas of high noise pollution.
Described as ‘acoustically insulating glass’, this option incorporates a specially manufactured interlayer to limit noise by up to 75%.
The interlayer also provides a shatterproof quality, for added safety.
COST: Up to 25% more expensive than standard glass, so it may be worthwhile installing this option in select windows, such as those at the front of the property if the property faces the main road.
7. Fire protection glass
As well as being fire-resistant for up to 180 minutes at temperatures of up to 870oC, this glass can also withstand smoke which can be even more detrimental to health.
The clear resin interlayers between the glass panes are fire-resistant, and the panes themselves are thicker than standard glass. The thicker glass also offers noise reduction, and UV protection.