Double Glazing Guide

Double Glazing:

All you need to know in our 10-minute guide to double glazed windows

DOUBLE GLAZING GUIDEMaybe you are moving to a new home or simply wish to renovate the one you live in. Whatever the motivation may be, if you are considering buying double glazed windows then this article should serve as a useful guide.

It’s important to understand your options to help in choosing double glazing windows that are the most suitable for your circumstances.

It goes without saying that all properties lose heat, especially through the windows, and installing energy efficient double glazed windows is one of the most effective ways to reduce your energy bills in addition to keeping your home quieter and more secure.

So to help you be prepared with enough information before you go out and get some quotes, this article is going to look at:

  • What is double glazing & double glazed windows?
  • What are the different types of double glazed windows?
  • Optional features for double glazed windows.
  • Double glazed window price guides.

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Double Glazing

& Double Glazed Windows Defined.

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Double Glazed Window

Double Glazed Window Internal View

All standard windows are single glazed; in that they were made of a single glass pane. Glass is generally a poor heat and sound insulator. It’s therefore easy for cold and hot air (as well as noise) to pass through, hence detracting from your enjoyment of your home.

Double glazing is an excellent solution to combat this by using two glass panes with a gap in between. The gap may contain a vacuum, partial vacuum or alternatively an inert gas.

This gap is key in leading to the reduction of sound and heat transmission, radiation and convection, serving as a massively better insulator compared to single glazing.

By having a vacuum, partial vacuum or a dense heavy gas (Argon / Xenon / Krypton) within the space between the panes of glass, it greatly lowers the instance of convection currents.

Convection, in this case, is the movement or circulation of whatever is inside the gap. So the double glazing unit within the window will depress or eliminate “circulation” of heat or cold from one side of the window to the other.

A vacuum is empty and is not capable of any type of convection or sound transmission (sound needs an atmosphere to travel – ask an astronaut!). Heavy inert gasses are harder for sound waves to move through and are much more resistant to circulation.

This is how double glazing windows keep the temperatures inside your house more regulated and can certainly save you money on energy bills, not to mention greatly cutting noise pollution from outside.

What are the different types of double glazed windows?

Double Glazed French Windows

Depending on your preferences, there are all sorts of double glazing windows tailored to various applications and climate. These defer according to the glass type, window frame material, shape, the space bar type and what will fill the space in between the glass.

Types of frame material.

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Choosing the right frame is very important as this would affect the window’s insulation properties significantly. The most common frame materials include PVC frames (uPVC), timber frames (made from hardwood) and Aluminium.

Clearly wooden window frames will be solid, but the frames for both aluminium and uPVC will have chambers, like a honeycomb. The chambers which run the full length of each profile is there to make the section lighter, stronger and more energy efficient.

Types of spacer bars.

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Spacer bars are the internal edging strips used to separate, and hold apart, the glass panes. They are typically made of either aluminium or low-heat conductive material and hollow. Within the hollow sections you will find a desiccant that is there to absorb any moisture that got in during manufacture.

Types of Glazing

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Low energy saving glass: Referred to as low-emissivity or Low-E glass, this glass type is especially used in very cold regions to save on energy.

Self-cleaning glass:Through modern surface coating technology, this glass can clean itself.

Acoustic glass: It’s built of two (or more) sheets of glass bonded together with acoustic inter-layers for sound insulation.

Safety glass: Unlike standard glass, this is a toughened and laminated form of glass does not form dangerous shards/ splinters when it breaks.

NB; Most of these glass types can usually be combined together to fulfill various individual needs.

Laminated glass: This glass acts as a greater protector than safety glass from vandalism or any form of aggression. It is a sandwich of float glass and a layer of PVB bonded together.

Fire glass: This is a greatly toughened, laminated and coated type of glass to protect you from fire and smoke.

Decorative glass: For improved functionality, this glass type is specially manufactured in various ways offering different choices of colours, patterns, texture and opacity.

Solar control glass: This glass type is made to reflect and filter the rays of the sun thereby allowing natural light without causing possible discomfort arising from visual glares especially for glass roofs and buildings with large areas that are glazed.

The most popular shapes and styles of Double Glazing Windows


Casement window


sash window


French Window

Optional Features for Double Glazing

Colours & finished surfaces for double glazed windows.

colour samplesThere are no restrictions on the colour for a timber window, as it is just a matter of choosing a suitable paint or stain, and maybe even change your mind afterwards and use a different colour.

With both uPVC & aluminium you choose the colour at outset and that’s what you stick with. Fortunately there are around 20 options for uPVC and a bewildering choice of over 100 finishes for aluminium double glazed windows – here are some:

  • White / Cream / Off-white / Ivory.
  • Blue / Green / Chartwell green / Grey.
  • Anthracite Grey / Black, Brown / Dark Blue.
  • Twin colour:  one colour outside, another colour inside.
  • Wood grain effect surfaces in both uPVC & Aluminium.

Pros of double glazing windows.

  • Can keep you warmer in winter and cooler in summer as already explained.
  • Reduces energy usage: Saving on your energy bills and ultimately helping the environment.
  • Reduces condensation: Double glazing works to reduce excess moisture on the window panes. This can be problematic as it can cause mold, mildew and other damage.
  • Reduces noise: Double glazing (high performance) can reduce noise from outside by about 60%.
  • Enhances resale value: Your home’s resale value can greatly be increased by double glazing as its desirable to purchasers.
  • Reduces interior fading: With the special glass types, the harmful effects of UV rays on carpet, drapes and furniture can be significantly reduced.
  • Increases security: Double glazed windows are more secure from intruders especially the toughened or laminated glass.

Cons of double glazing windows.

  • Trapped heat: Though trapping heat is necessary in cold seasons; this has a different effect in summer. The windows can however be tinted to solve the problem.
  • Can’t be repaired: Double glazed windows are difficult to fix. This can be especially true when dealing with double glazing that has been installed for a few years. Spare parts can become rarer to find and that can entail replacing the whole window as the only solution.
  • Might not match/blend well with older houses: For period homes, or those of a particular character, the average double glazed window designs may not suit the property. In this case you would need to have a bespoke set built to order.

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Double glazed window price guides.

How much do double glazed windows cost?

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Prices for the different types of windows will be impacted by the size, the energy ratings and the level of finishing (extras) that you select for your home.

For example, with uPVC you can expect to find a colored window cost between 10 to 20% more than a white one. With timber windows, hardwoods will cost more than softwood or engineered wood.

Window sills (cills) and trickle vents may not be included in the basic prices and some charge for a little extra for each  window section that you want to be able to open.

So, bear in mind that you need to confirm the full cost with your supplier / installer at outset.

How much do casement windows cost?

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Window Size in MM Frame Material Fully Fitted Price
600 x 900 uPVC  Around £200
1200 x 1200 uPVC Around £300
940 x 1600 uPVC Around £450
Semi-detached 3 bed house uPVC £4,500 to £6,000

How much do sash windows cost?

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Window Size in MM Frame Material  Fitted Price Guide
600 x 900 White uPVC from £500
1200 x 1200 White uPVC from £600
Semi-detached 3 bed house Timber £10,000 upwards

How much do French windows cost?

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Window size in MM Specification Average Price Guide
1200 x 1200 White uPVC, clear glazed from £300 to  £400
1200 x 1200 White uPVC, Georgian bars, clear glazed from £350 to  £400
1000 x 1200 White uPVC, clear glazed from £300 to  £350
 1000 x 1200 White uPVC, Georgian bars, clear glazed from £350 to  £390


Always use an installer who is accredited with FENSA or CERTASS so that you can have your windows certified as compliant with UK building regulations.

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