What Are the Different Types of Double Glazing Glass?
Double glazing glass options for replacement windows
Whilst the material used for the frames of your windows may be down to personal preference, proper attention should be given to the properties of the glass itself.
Different types of glass may be optional in some areas, but may be a regulatory requirement in others.
Here is our basic buyers guide to the (most often used) different types of double glazing glass.
- Float glass – Pioneered by Sir Alastair Pilkington in 1959 and accounts for around a very high percentage of the way flat glass is made these days.
- Toughened glass – sometimes called Tempered, it’s about 4 or 5 times more difficult to break than float glass.
- Laminated glass – a “sandwich” consisting 2 layers of glass with a “filling” of either PVB (plastic) or resin.
Float Glass: How thick should the panes be in my double glazed windows?
Modern new or replacement windows will typically fit “float glass”. The standard thickness of the glass will be 4mm.
Slightly thicker glass, at 6mm, can be used to help improve both the insulation and sound deadening properties of the sealed unit.
Bear in mind that using thicker glass may result in a thinner air gap between the panes in some cases where you need to keep your frames slim. Adding argon gas to the sealed unit can compensate for the reduced space between the outer and inner panes of glass.
Under normal circumstances, 4mm float glass is perfectly acceptable to use for your double glazed windows in non-vulnerable (high traffic or low level) areas.
If you suffer from low frequency sounds outside, such as traffic, 6mm thick glass can be more effective at reducing sound penetration. It’s also worth considering using different thicknesses in each side of the unit to combat the noise. Check with your surveyor.
Toughened or Tempered Glass
Around the home there will be places where windows or doors are fitted in a vulnerable or critical area. The perfect example is a patio door where the glazing reaches floor level.
In a nutshell, where glazing comes to within 800mm of floor level, toughened safety glass is required. Not only to meet building regulations, but to protect adults or children from serious injury in the event of the glass breaking.
- Good explanation about safety glass regulations here: https://www.leadbitterglass.co.uk/glassroom/safety-glass-regulations/
- UK planning portal here: https://www.planningportal.co.uk/info/200130/common_projects/14/doors_and_windows/2
The standard example is going to make use of 2 x 3mm panes of float glass. The inner layer may be around 0.4mm, giving a total thickness of 6.4mm.
There are 2 types of production:
- PVB laminated: which can make use of 2 or more panes that are bonded to each other by 1 or more layers of polyvinyl butyrain (PVB). These layers under heat & pressure during the manufacturing process become as one piece.
- Resin laminated: The manufacturing process involves introducing liquid resin filling into a gap between two sheets of glass. The resin cures within in the gap and forms a single sheet of laminated glass.
The beauty of laminated glass is that if you break it, the pieces stay stuck to the resin or PVC core – no sharp shards or hundreds of tiny pieces of glass to injure anyone.
This type of glazing is perfect where you want added security, as it is extremely difficult to break through in order to gain entry into a property. Lots of this type of glazing can be seen in shopfronts.
If you want to check if you have toughened or laminated glazing fitted, then look for the British Standard test reference and the letter L for laminated, and T for toughened.
Another way to simply check if you glass is tempered or toughened is to look at it using polarised sunglasses. In this way you will be able to see the heat treatment marks on the glass. Rotating the sunglasses will make the marks visible or invisible.
In most cases, 4mm float glass is fine to use as your standard double glazing glass choice. 6mm glass can help improve insulation and reduce noise ingress.
Toughened or tempered glass must be fitted in vulnerable areas as a regulatory requirement.
Laminated glass is excellent for extra security & safety.