There' never been a wider choice for homeowners when purchasing brand new double glazing. We're all very familiar with the different types of frame - uPVC, timber, and aluminium. We also know the type of window we want for our homes too - casement, sash, tilt and turn, and so on. But how much do you know about the types of glass used in double glazing?
You might be surprised to hear that there are eight main types of glass used in double glazing installations in the UK including:
- annealed (or float) glass
- tempered (or toughened) glass
- laminated glass
- low E glass
- self-cleaning glass
- noise control glass
- fire protection glass
The best way to find out which is the right type of glass for you is to speak with a professional and experienced installer. Here at CompareCompanies, we work with hundreds of reputable and established double glazing companies with strong and reliable track records of customer satisfaction, quality materials, and industry-leading professional installation.
It’s even better to speak to three or four at once because encouraging competition between installers has been shown to bring down the size of the quotes you receive by up to 40%. We’ll put you in touch with these installers at no charge and you’re under no obligation to accept any of the quotations you’re offered.
Annealed (or float) glass
Annealed glass (or float glass) is manufactured using a process known as the Pilkington process. Most modern windows are made using this process – it involves floating molten glass on a facet of molten tin (or another metal) and this method gives the glass the very same thickness throughout and the desired surface flatness. Every other type of glass mentioned in this article starts off as annealed glass.
Float glass is the least expensive type of glass on the market however its affordability does not affect its suitability for use in double glazing, triple glazing, or in conservatories in people’s homes.
Annealed glass is very strong and it can withstand six thousand pounds per square inch of pressure. To put that into context, six thousand pounds per square inch of pressure is equivalent to the weight of a grand piano concentrated into one square inch.
Because of the way that double glazing is manufactured, it’s very difficult to break or smash it no matter what type of glass it’s made from – and that includes competitively-priced annealed glass.
This is how double glazing works. Within a double glazing frame, there are two panes of glass held in position between which is a gas, like argon, which is heavier than the air in the general atmosphere.
It’s the heaviness of the gas between the panes which makes double-glazing really strong. If something is thrown at one of these double-glazed windows with force, the argon naturally pushes back against the object that’s hit your window. This pushing back gives your double glazing enormous strength and, at the same time, it provides sound-proofing against noise from the outside and its superb insulation properties.
Annealed glass is thin, light, strong, and malleable – those qualities together with its competitive price make it the most popular choice for British homeowners.
Tempered (or toughened glass)
Up to 25% more expensive than standard glass, tempered or toughened glass is popular among homeowners whose budgets can accommodate the extra expense because it has a longer lifespan. It generally keeps its optimum condition for up to 5 or 10 years longer than annealed glass so you don’t have to replace it as often meaning that it may actually end up costing you less over time.
Toughened glass is manufactured by placing a pane of annealed glass in an oven for baking. The oven Is set at a very high temperature of 620°C and after a short time in the oven, it’s then immediately and quickly cooled straight away in water.
As opposed to standard glass which, if it breaks, shatters into long shards, toughened glass breaks into very small pieces putting your family (and particularly your children) at a much reduced chance of sustaining an injury. Manufacturers of shower doors and glass-covered tables choose tempered glass for this very reason.
There may be a time when an installer insists that you use toughened glass in your home. Current Building Regulations stipulate that tempered glass must be used for:
- any window fitted 800mm or lower from floor level,
- any window 300mm or less from a door and up to 1500mm from the level of the floor, or
- on any glazed door up to 1500mm from floor level
Toughened glass can withstand twenty-four thousand pounds per square inch of pressure before breaking – that’s the same as 1.7 tyrannosaurus rex or the anchor of a cruise ship placed on one square inch of the window pane.
However, please bear in mind that, when your toughened glass double glazing is being fitted, you should make sure that your installer drills the absolute minimum number of holes needed into a pane because these screws significantly weaken the strength of the glass.
Laminated glass is even safer than tempered glass when shattered – it’s safer because of a special interlayer made of plastic which covers the entire pane. The interlayer is made out of either ethylene-vinyl acetate or polyvinyl butyryl and this interlayer actually holds the glass is place if your window is broken. This further reduces the chance of injury to family members.
As well as being heavily used in the double glazing industry, laminated glass is also used on shopfront windows (where broken glass on the floor would cause a risk to shop staff, customers, and passers-by) and on your car windscreen.
Laminated glass offers additional protection against forced entry burglary because, when broken, the plastic interlayer holds so tightly and strongly in place that there is not enough room for a thief to climb through it. In addition, in recent years, some laminates used on double glazing offer enhanced protection against UV rays protecting the colours of your carpet and your furniture from prolonged exposure to the sun.
Laminated glass is up to 40% more expensive than standard glass
Low E glass
“Low energy” or Low E glass is specially manufactured for homeowners wishing to save as much money on their electricity and gas bills as possible by reducing their reliance on their central heating and cooling systems.
Low E glass is coated with a transparent metal film which reflects heat from your rooms back into your home and allows light and heat from outside to pass through the panes. While all modern, energy-efficient double glazing offers these features, the low E does it better because of this special metal film.
Depending on which company supplies your installer, there are two types of Low E glass currently on the market in Britain.
If you’re offered a “hard coat” method, your double glazing panes will be manufactured by Pilkington. When a pane of glass is hard-coated, the manufacturer adds a very thin layer of molten tin onto the sheet of glass while the glass itself is stolen molten hot. The molten tin and the molten glass then fuse meaning that the tin becomes incorporated into the final pane – as a result, they have a stylish grey or light blue tint to them.
The “soft coat” method is offered by Saint Gobain. With soft-coating, atomised tin, zinc, or silver is released into a vacuum chamber along with the pane of glass and a gas with electrical charge. This atomised silver, zinc, or tin is then sprayed onto the surface of the pane – similar to the way that gold-plating or silver-plating is added to jewellery. Only one side of each pane is sprayed and, when your double glazing frame is being manufactured, the sprayed sides always face inwards towards the inert gas in the layer between.
Low E glass generally costs up to 25% more expensive than standard glass. However, if you live in a large property and your heating bills are high, the amount you save every year on your utility bills may be equal to or more than the premium you pay for your Low E glass.
Up to 20% more expensive than standard glass, self-cleaning glass’s stand-out property is that the way it is constructed means that the glass facing the outside of your building will clean itself, whether it’s been raining or not.
Your toothpaste and any white paint you’ve used to decorate your home contains an element called titanium dioxide. Self-cleaning glass uses this same element – it’s placed on your window panes during manufacture as a thin layer. In fact, the layer is so thin that it’s completely transparent and your window still lets in nearly as much light as a standard annealed window – 95% or more.
When the UV rays of the sun come into contact with the titanium dioxide, the electrons within the film are stimulated and the effect of that is that it extracts water molecules from the air and brings them towards the surface of your window. When the water and titanium dioxide come into contact, there is a chemical reaction which creates something called “hydroxyl radicals”. Those radicals start to break down the composition and structure of anything organic on your window. All of the marks and dust on your window are then washed away when it starts to rain.
Self-cleaning glass also works when it doesn’t rain. The titanium dioxide still grabs water molecules from the air and this water starts to spread itself evenly over the surface of your window pane like a film. Over time, gravity starts to force the very thin film of water down your window washing away the broken-down dust, marks, and any other matter.
Please be aware that you will still have to clean the glass on the inside of your home and that self-cleaning glass is of limited use in areas with high airborne salt or pollutant levels.
Self-cleaning double glazing carries a premium of up to 25% over and above the cost of standard annealed glass.
Noise control glass
Noise control glass, often referred to by installers as acoustically-insulating glass, is ideal for homes underneath flight paths or near very busy roads. To control the level of sound coming into your home, noise control glass uses a special interlayer manufactured to reduce the level and the range of noise reaching the inner pane of your double glazing. Independent tests have confirmed that there is up to a 75% reduction in sound and sound levels when noise control glass is installed.
The interlayer also provides the same shatter-proof protection offered by laminated glass for extra safety around your home.
Noise control glass is up to 25% more expensive than standard glass so you may wish to choose to use it on windows facing a busy road, for example. If the back of your home is much quieter, you may save money by choosing a different type of double-glazing for these less noisy areas.
Fire protection glass
Fire protection not only holds back fire – it holds back smoke too. Smoke is, in many ways, more injurious and deadly than fire itself and fire protection glass can be manufactured to provide protection for 30, 60, 90, 120, or 180 minutes – ask your installer for advice for your situation.
Whereas normal glass shatters at 500°F, fire protection glass offers protection at temperatures of up to 1,600°F. They do thing by using clear resin interlayers which are placed between the panes of glass in your frame. The interlayers are fire-resistant and the panes of glass used are much thicker than the panes in more standard installations. A by-product of the thicker glass and the additional interlayers is enhanced protection from the sun’s UV rays and against noise from outside.
Get a range of quotes of double glazing you’ll love
There’s more choice available to you than ever before with double-glazing for your home. Both the technology and the manufacturing processes have significantly progressed in the last 20 years meaning that there’s far more choice available to homeowners now than ever before at lower prices.
The type of glass you choose for your double glazing installation is important. You don’t have to choose the same type of glass for every window in your home either – the choice is truly in your hands.
At CompareCompanies, we put homeowners in touch with experienced, qualified, and certified double-glazing companies across the UK – all of our installers are FENSA or CERTASS registered. Our service is free and there’s no obligation on you to accept any quote given to you by our chosen installers.
By getting companies to compete with each other for your business, you could save up to 40% on your installation. And because double-glazing is such a major investment in your home and in your family’s comfort and security, it pays to work with a company you feel you can trust at a price you can afford.