What Is The Best Glass For Double Glazing Windows?

Double-glazed windows are some of the most popular choices for new windows and doors in homes across the UK, and for good reason. Two panes of glass are separated by a gas-filled vacuum chamber that acts as a barrier to prevent warm air from escaping from the house and stops any cold air from getting in, promoting optimal energy efficiency. Even in the summer, it keeps hot air outside so the inside of your property remains cool. This means you’ll enjoy significant savings on your heating bills, so you can turn your central heating down or off, decreasing your overall carbon footprint.

With other features like noise reduction, vital in busy areas, installing double glazing is a no-brainer! But what are the different options for the type of glass used in your double glazing, and which is best?

Our informative article reviews the range of different glass types offered by double-glazing companies for new double-glazed windows.

What Is The Best Glass For Double Glazing?

Many people don’t realise that double glazing units come with different glass options; after all, glass is glass, isn’t it? But there are very important decisions to make when choosing the right kind of glass for your double-glazed windows, dictating your home’s energy efficiency, security, and how personal your windows will be. You can get an idea about how different glass types might work with different materials for your windows when you build your perfect window using our online quote tool.

The two most popular glass types used for double-glazed windows are annealed and toughened. Annealed glass (also known as ‘float’ glass) is the most affordable option. It has been used for decades because of its durability and ability to act as a shock absorber against impacts, making it incredibly secure. Toughened (or ‘tempered’) glass is far stronger than annealed glass and less likely to break. It breaks into small fragments if it does shatter, 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, float glass has a high-quality, smooth finish and even thickness. While it is more likely to shatter when broken, float glass remains the most affordable glass option. It is the most popular choice for double glazing as it is incredibly durable and long-lasting.
• Tempered Glass – Processed through a chemical or thermal treatment to make it far stronger than ordinary glass, tempered glass is designed to safely crumble instead of shattering if broken, making it far less dangerous to dispose of. Significantly more durable than ordinary glass, it can survive large amounts of excess force without breaking.
• Self-Cleaning Glass – A contemporary option for low maintenance, self-cleaning glass prevents grime or dirt from building up over time. The glass is covered in a titanium dioxide coating that breaks up the dirt into smaller pieces and allows it to be washed away by the rain without any need to wipe down. This glass is an excellent choice for roof lights, skylights, or difficult-to-reach windows around the house.
• Laminated Glass – Also known as ‘safety glass’ it is far tougher than tempered glass. It has a plastic layer of either ethyl vinyl acetate or polyurethane placed between the two panes of double glazing. This layer of plastic prevents the glass from falling out if it is broken, holding the shattered glass in place and preventing an intruder from gaining entry to your property. Laminated glass is very popular for commercial properties and shopfronts to prevent theft.
• Fire-Proof Glass – Fire-resistant glass is specially manufactured to provide enhanced protection from fire. It can survive high temperatures and proximity to flames for 30 to 180 minutes on average, giving occupants enough time to escape and firefighters more time to stop the fire before it breaches the glass. While normal glass breaks at around 260°C (500°F), fire-resistant glass can withstand temperatures as high as 871°C (1,600°F).
• Coated Glass – Also known as ‘Low E glass’ or low emissivity glass, this glass is covered in a Pyrolytic coating during the float-glass manufacturing process, giving it enhanced durability and creating a far more thermally efficient glass. Coated glass helps improve insulation by trapping heat within your home, reducing heat loss and heat transfer, allowing you to decrease your reliance on expensive 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?

The rating system informs consumers about different glass types and the most energy-efficient types of double-glazed windows. Since 2010, it has been a requirement that all new window and door products have a minimum rating of C as part of measures to reduce environmental impact. The most thermally efficient windows have an A+ rating.

There are several different rating schemes, with the British Fenestration Rating Council and CERTASS ranging from E to A+ (the Fenestration Rating Council includes an A++ rating), while the British Standards Institute system goes from G to A+. These ratings also include a measurement of a window’s light energy transmittance and heat retention.

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

Most people focus on how energy efficient the glass in their double-glazed units is, as good insulation means a warmer, more comfortable home and lower energy bills. With ratings ranging from G to A+, the higher the rating, the better insulated the window is. But what is the difference between the A and A+ ratings, and does it make that much of a difference?

While ‘A’ was initially set as the highest rating for double glazing and uPVC (unplasticised polyvinyl chloride )windows, advances in manufacturing techniques in recent years mean that now, some windows exceed that ‘A’ standard, gaining a rating of ‘A+’ or ‘A++’. This added rating just means that the windows you are looking at offer the highest standards of energy efficiency available. Unfortunately, higher-rated windows come at a higher cost, but they offer excellent value for money over the long term. You’ll have to balance the energy savings you can make with new rated windows compared to your existing ones against the unit price of new double-glazed windows.

It is essential that you get the most energy-efficient windows for your home. So, what are the standards for double-glazed windows?

There are, in fact, documents available freely online that allow you to find out the current energy efficiency of your home and any new windows you plan on installing. The standards for glass and glazing are the Harmonised European Norms (HENs), which dictate the technical standards for all windows manufactured and sold within Europe. Windows that comply with these regulations are labelled with a CE logo, and whilst it is not compulsory in the UK, you should always look out for it when buying new double-glazed windows and doors.

U-values measure the insulation and thermal efficiency of a window. The U-value determines how thermally secure a window is and how much heat is transferred to the outside through the glass. The higher the U-value, the more heat is transferred, meaning that lower U-values are much more sought after for double-glazed windows.

U-values for double glazing are 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 transmitted per square meter across the pane.

The standard U-values for glass vary 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

All our trusted local suppliers are members of one or more of these consumer protection groups

Frequently Asked Questions

How Can I Work Out The Best Glass For My New Windows?

The best type of glass for your property depends on a few factors, such as what you are using your windows for, what kind of property you have, and how much energy you want to save. Many people are driven by lowering their energy bills, but if you live in a location with a lot of external noise, soundproofing will be high on your list of priorities too. The best advice is always to purchase the hardest wearing glass with the lowest U-Values and highest energy rating, but often your budget will dictate just what kind of windows you can afford. The most frequently recommended type of glass for double-glazed windows is tempered or safety glass, which is durable, heat-retaining, and stronger against any excess force, keeping your property warm and secure.

What Is The Best Glass For Doors?

If you are looking to get a glass door, double-glazed laminated glass is often the way to go. It is incredibly robust, with two sheets of polyvinyl inside each layer of glass. If it were to break, any smashed glass fragments would remain held together inside the frame to prevent anyone from trying to enter your home by climbing in through a hole.

What Is The Best Glass For Conservatories?

Conservatories are unique in that they are almost always made entirely of glass, meaning they can suffer from solar gain. Solar heat gain is the passive acquisition of heat and natural light, which happens in conservatories because of their structure. Solar control glass is one option you can consider, but ultimately, 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 you might also want to consider self-cleaning glass, which can save you a lot of time and effort, especially if you have a glass roof that may be difficult to access and properly clean.

What Is Solar Control Glass?

Solar control glass is a specially designed type of glass that controls the amount of natural light and solar heat that enters a building. Solar heat can be a problem in south-facing rooms with many windows and conservatories. Solar control glass usually has a metal oxide coating that reflects infrared radiation while still allowing visible light to pass through it. Solar control glass minimises overheating in conservatories and rooms with French windows or patio doors.

I am looking for new windows for my period property. What type of glass is best?

If you own a period property or a listed building, you’ll know all about expensive heating bills if you have single-pane windows. Replacement double-glazed windows or even triple-glazed windows can reduce noise and your energy bills in one hit. However, aesthetic appeal is also very important, so you may feel that uPVC frames will not suit your home. Fortunately, plenty of other materials in the marketplace can be combined with a range of different glass types to suit your requirements, creating a sealed unit that will manage noise, solar gain, and promote energy efficiency. Modern sash windows are available with double and triple glazing with wooden frames or imitation timber frames – you really won’t be able to tell the difference, until you look at the price!