Best Glass for Double Glazing

When buying new windows for your home, double glazing remains one of the most popular options for glass available on the market, and for good reason.

With two panes of glass, they are separated by a gas-filled vacuum chamber that thickens the glass and acts as a barrier to prevent warm air from escaping the house and stops any cold air from getting in from outside. Even in the summer, it allows for warm air to remain outside, keeping the inside of your property cool. This allows for you to save a lot of money on your heating bills, stopping you from over-relying on your central heating and helping you to decrease your overall carbon footprint.

Getting double glazing is a no-brainer for when choosing your new or replacement windows, but what are the different options for the glass used in your double glazing? And which one is the best?

What Is The Best Glass For Double Glazing?

It may come as a surprise to you that double glazing comes with different glass options; after all, glass is glass, isn’t it? But there are actually very important decisions to be made when choosing the right kind of glass for your double-glazed windows, dictating just how thermally efficient, secure and personalised your window will be.

The two most popular glass types used for double glazed windows are annealed and toughened glass. Annealed glass (also known as ‘float’ glass) is the most affordable option out there and has been used for decades because of its durability and ability to act as a shock absorber against any blows against it, making it incredibly secure. Toughened (or ‘tempered’) glass, however, is far stronger than annealed and is far less likely to break; if it does break, however, it fragments into small chunks instead of leaving large, jagged shards within the window frame.

Float Glass – Named after its manufacturing process of floating the molten glass in a ‘bath’ of molten tin or lead to create a high quality, smooth finish and give it an even thickness. While it is more likely to shatter when broken, float glass is the most affordable glass option and the most popular option for double glazing, still being incredibly durable, long-lasting and strong.

Tempered Glass – Processed through a chemical or thermal treatment to make it far stronger than typical glass, tempered glass is designed to safely crumble instead of shattering in the event that it is broken, making it less dangerous to dispose of. Far more durable than normal glass, it is able to survive large amounts of excess force without breaking.

Self-Cleaning Glass – A contemporary option for low maintenance, everyday use that prevents grime or dirt from building up over time. The glass itself is covered in a titanium dioxide coating that breaks up the dirt into smaller pieces and allows them to be washed away by the rain without any need to wipe it down. This glass is an excellent choice for roof or skylights or difficult to reach windows around the house, making keeping them clean an easy matter of waiting for the rain.

Laminated Glass – Also known as ‘safety glass’, this glass is far tougher than even tempered glass, with a plastic layer of either ethyl vinyl acetate or polyurethane put between both panes of double glazing. This layer of plastic prevents the glass from falling out in the event that it is broken, holding the broken glass in place and meaning that the person trying to break in cannot climb through a hole in the window. Very popular for commercial properties and shopfronts, preventing any thefts.

Fire-Proof Glass – Fire-resistant glass is specially manufactured to provide far greater protection from fire than other types of glass, being able to survive high temperatures and proximity to flames from 30 to 180 minutes, giving you enough time to escape and giving the firefighters longer to stop the fire before it breaches the glass. While normal glass breaks at around 260°C (500°F), fire-resistant glass is able to withstand temperatures as high as 871°C (1,600°F).

Coated Glass – Also known as ‘Low E glass’, this glass is covered in a Pyrolytic coating during the float-glass manufacturing process, giving it increased durability and allowing it to be far more thermally efficient, helping to trap heat within the home and reducing your reliance on your central heating.

You may have noticed when researching different types of windows that each window has its own rating, from G to A+. But what exactly does that mean?

Since 2010 is has been required for all windows sold in the UK to have a minimum rating of C, helping to reduce our impact on the environment. These ratings mean that the higher the rating of the window, the more thermally efficient it is, with A+ being the highest and the best for thermal insulation. There are a few different rating schemes, with the British Fenestration Rating Council and CERTASS counting from E to A+ (with the Fenestration Rating Council including a rating of A++), while the British Standards Institute rates from G to A+. These ratings also include a measurement for the amount of light energy transmittance and heat retention in a window.

Getting high rated glass for your windows increases your window’s thermal efficiency, saving you money on your heating bills and helping you to decrease your overall carbon footprint.

With the rating ranging from G to A+, obviously, the higher the rating the better insulated the window is. But what is the difference between the A and A+ rating, and does it make that much of a difference?

While ‘A’ was originally set as the highest rating for double glazing and uPVC windows, there have been advances in manufacturing techniques over recent years, meaning that some windows exceed that ‘A’ standard, instead gaining the rating of ‘A+’ and ‘A++’. This added rating just means that the windows you are looking at exceed the highest standard of energy efficiency currently set. Unfortunately, the higher the rating of the window the more it will cost, meaning that you may have to balance how energy efficient you need your windows to be with how much you are willing to spend.

It is important that you get the very best windows available for your home, so what are the standards for double glazed windows?

There are in fact documents available freely online that allows you to find out the energy efficiency of your home and any new windows you are planning on having installed. The standards for glass and glazing is the Harmonised European Norms (hENs), which dictate the technical standards for all windows manufactured and sold within Europe. Windows which comply this these regulations are labelled with a CE logo, and while it is not compulsory in the UK, should always look out for when purchasing a new window.

U Values are the measurement of the insulation and thermal efficiency of a window, used to determine how thermally secure a window is and how much heat is being transferred to the outside through the glass. The higher the U Value is, the more heat is being transferred, meaning that lower U values are much more sought after for windows.

U values for double glazing is typically measured in watts per square meter per degree kelvin (W/m2K), with a U Value of 3.0 meaning that 3.0 watts of heat are being transmitted per square meter across the pane.

The standard U values for glass varies depending on the type of glazing you have:

Single glazing – 4.8

Double glazing – 2.8

Low E Double glazing – 2

Triple glazing – 1.5

The best type of glass for your property is dependant on what you are using your windows for, what kind of property you have and how much energy you want to save. It is recommended to get the hardest wearing glass with the lowest U-Values and highest energy rating possible, but often your budget will dictate just what kind of window you can afford.

The best-recommended type of glass for windows is tempered or safety glass, which is far more durable, heat retaining and stronger against any excess force, keeping your property warm and safely secure.

If you are looking to get a glass door, double glazed, laminated glass is often the way to go. Incredibly strong and with a layer of polyvinyl inside each layer of glass, in the unlikely event that it was to break, any smashed glass remains held together inside the frame to prevent anyone trying to enter your home from climbing in through a hole in the smashed glass.

Like windows, the best choice of glass for your conservatory depends on what you want to use your conservatory for and how much energy you want to save. Double glazing is now often considered the standard, but having self-cleaning glass for your conservatory can save you a lot of time and effort, especially if you have a glass roof that may be difficult to access to properly clean.