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Welcome to the Windows FAQ & Resources Section

Let us help you with all of your window questions and find the perfect addition to your home.

How does double glazing work?

Find out exactly how double glazing and triple glazing works, the ins and outs of their energy ratings and how improving your windows will help you save money and reduce sound pollution.

What is the U-value of Anglian's triple glazing?

A whole house of Anglian's triple glazed windows

Anglian uPVC triple glazed casement windows have a U-value of 0.9, whilst Anglian uPVC triple tilt & turn windows have a U-Value of 1.0.

How does triple glazing work to save energy?

Anglian Triple Glazed Windows

Triple glazing works by trapping more heat in your home. The Low E glass works brilliantly at reflecting heat back into your home, preventing it from escaping. By doing this, your home takes less time and money to heat as less is escaping out of your windows therefore saving you energy!

What is double glazing and how does it work?

White Knight uPVC casement window

Double-glazing is a window consisting of two panes of glass separated by a layer of trapped argon gas. The layer of argon gas has 67% of thermal conductivity of air, making it a poor conductor of heat, thus keeping warm air trapped inside your home and helping improve energy efficiency.

This extra pane of glass also acts as a secondary barrier to noise, helping keep your home nice and quiet, and strengthens the window to improve security.

What is triple glazing?

White Knight uPVC triple glazing

Triple glazing is a window with 3 panes of glass offering the ultimate energy efficiency in any Anglian products. At Anglian these 3 panes of glass will be within an uPVC frame, available in a range of colours.

The frame includes a thermal insert in the mainframe chamber to create smaller chambers and reduce heat loss. There’s a spacer bar between each pane of glass which is made from thermally optimised insulating material, which prevents heat escaping round the edge of the sealed unit.

In the space between the panes is Krypton gas, an inert gas that increases the window’s thermal performance. This gas is what has helped create our best window ever with an Energy Index of +32, which simply means it will gain 32 kilowatt hours of energy per square metre per year.

Learn more about triple glazing.

What is secondary glazing?

Anglian secondary glazing

Secondary glazing involves adding a second, ‘slim-line’ window just inside your existing window reveal and is ideal if you are unable to install double or triple glazing due to planning restrictions.

Secondary glazed windows are subtle and, therefore, won’t impact heavily on the building’s aesthetic, but they still have many of the properties of double glazing, helping to keep your home warmer, quieter (if required) and save you energy and money.

Learn more about secondary glazing.

Does double/triple glazing keep out noise?

White Knight uPVC triple glazing

Yes, it does! While it won’t completely block out all noise, installing double or triple glazing can significantly reduce the noise you hear from outside. The amount of noise the windows blocks out can depend on factors including vent size, the age of the windows, etc.

If you need additional noise protection (if you live by an airport, for example), then our Safe & Sound double glazed casement windows provide 36dB of sound reduction.

Does double / triple glazing reduce your utility bills and energy usage?

White Knight uPVC casement windows

If you’re replacing older units you can be pretty confident it will save energy and therefore money on your bills. This does depend on the type of window you choose - all our window styles have a range of different energy efficiency ratings. We can calculate the amount you might save on your energy bills using the Glass and Glazing Federation’s energy calculator. As an example, a detached house with 23.7m² of windows and electric heating upgrading from single glazed wooden windows to A-rated casement windows could save £325.26 a year.

Window Energy Ratings explained

White Knight uPVC triple glazing

When buying new windows, one of the most important things to look out for is the Windows Energy Rating (WER). They work in a similar way to the energy ratings on electrical goods.

The ratings go from A++ (very efficient like our triple glazed windows) to G (incredibly inefficient). To comply with building regulations, all windows have to be at least C-rated.

The Windows Energy Rating is calculated using various values:

  • Thermal Transmittance (U value)
  • Solar factor (G value)
  • Air Leakage (L value)

U-value - how much heat can escape through the glass (thermal transmittance), measured in Kilowatt-hours, per square meter, per year.

For example: 2.5kWh/m2.K

This means that 2.5 kilowatts of energy is lost through every square metre of the window every year – that’s every square metre of window boiling the kettle!

G-value - how much energy gained through your windows from the Sun (solar factor). This is measured in kilowatt hours per metre, per year.

L-value - Air leakage through the window. We’re looking for as low as possible here and is measured in kilowatt hours per metre, per year.

View our energy efficient windows.

Why does my double glazing suffer from condensation?

Dual white uPVC casement windows

Having double glazing should reduce condensation and mist build-up as the inner pane is warmer than the outer pane, thus acting as a heat barrier. However, if you are noticing condensation or mist forming in between the panes of glass in your double glazing, then this could be due to a fault in the sealed unit.

You might not even be able to see the fault, but even the smallest hole can let air pass through, increasing the chances of moisture build-up.

If you are getting condensation on the outside pane of glass, it shows how well your windows are performing as the heat from within your home isn’t escaping, keeping the outer pane cooler than the outside air.

However if you have condensation on the internal pane of glass, it is probably caused by poor ventilation. For example, if you don’t have an extractor fan in the bathroom, then moisture from the bath and shower will settle as condensation. Opening a window can help reduce condensation until the problem is fixed.

Why is there a draught coming from my double glazing?

White wooden sash window

Your double-glazed windows are sealed units and, therefore, should not let any draughts pass through them. If you are feeling a draught from your double glazing, it could be something as simple as a vent is open or it could be more serious and could be due to a fault in the seal around the frame. Make sure that the frame is airtight to the brickwork.

If you have a window that opens then a draught could be caused by the window not being shut properly, so double check that there are no faults with the locking mechanism and that the window fits snuggly against the frame when closed. Any gaps could let in air and cause a draught.