Double Glazing

• Smaller energy bills: replacing all single glazed windows with energy efficient glazing could save you around £135 per year on your energy bills.
• A smaller carbon footprint: by using less fuel, you’ll generate less of the carbon dioxide (CO₂) that leads to global warming.
• A more comfortable home: energy efficient glazing reduces heat loss through windows and means fewer draughts and cold spots.
• Peace and quiet: as well as keeping the heat in, energy efficient windows insulate your home against unwanted outside noise.
• Reduced condensation: energy efficient glazing reduces condensation build-up on the inside of windows.

Replacement windows come in a range of styles and designs and there are particular features you should look out for to increase energy efficiency.

To find the right windows for your home, ask yourself these questions:

How energy efficient are the windows?

When choosing replacement windows, you can check its energy efficiency by looking at the Energy Saving Trust Recommended logo and BFRC energy label. The Energy Saving Trust endorses any windows rated B or above. The higher the energy rating, the more energy efficient it is. Unfortunately, at the moment there is no obligation for window manufacturers to label their products, however by opting for a high rated window you know you will be buying the most efficient.

For a list of all windows and their frame material and energy rating, visit the BFRC website.

How many layers of glass do you need?

Double glazing has two layers of glass with a gap of around 16mm between them. There’s also the option of triple glazing, which has three layers of glass. Both A rated double and tripled-glazed windows are available.

What type of glass is best?

The most energy efficient glass for double glazing is low emissivity (Low-E) glass. This often has an unnoticeable coating of metal oxide, normally on one of the internal panes – next to the gap. It lets sunlight and heat in but cuts the amount of heat that can get out again.

What’s between the panes?

Very efficient windows might use gases like argon, xenon or krypton in the gap between the 2 sheets of glass.

What keeps the panes apart?

All double glazed windows have pane spacers set around the inside edges to keep the two panes of glass apart. For a more efficient window, look for pane spacers containing little or no metal – often known as “warm edge” spacers.

The BFRC window energy rating scheme checks all the components to ensure the final window achieves the energy efficient standard claimed. This means that you just need to look for the A-G ratings and remember A is best! Alternatively, just look for the Energy Saving Trust Recommended logo which will only be found on glazing that is B rated or above.

Which frame suits your home?

The frame you choose will depend on your home and your personal taste. For all frame materials there are windows available in each energy rating.

• uPVC frames are the most common type. They last a long time and can be recycled.
• Wooden frames can have a lower environmental impact, but require maintenance. They are often used in conservation areas where the original windows were timber framed.
• Aluminium or steel frames are slim and long-lasting. They can be recycled.
• Composite frames have an inner timber frame covered with aluminium or plastic. This reduces the need for maintenance and keeps the frame weatherproof

Do you need ventilation?

Because replacement windows will be more airtight than the original single glazed frames, condensation can build up in your house due to the reduced ventilation.

If there is not a sufficient level of background ventilation in the room some replacement windows will have trickle vents incorporated into the frame that let in a small amount of controlled ventilation.

Condensation can sometimes occur on the outside of new low-e glazing. This is because low-e glass reflects heat back into the home and as a result the outside pane remains cool and condensation can build up in cold weather – this isn’t a problem.