How Much Does Double Glazing Cost for a UK Home in 2026?

Average Double Glazed Windows Costs

Before adding installation costs, the two main factors that determine the price of a double glazed window are the frame material and the window design.

• Common frame materials in the UK: Unplasticised polyvinyl chloride (uPVC), aluminium and timber.
• Common window designs: Casement windows, sash windows, bay windows, bow windows, and tilt and turn windows.

Double glazed windows with uPVC frames are the most affordable option. Aluminium is more expensive than uPVC, and timber is more expensive than aluminium. uPVC and aluminium windows require little maintenance beyond regular cleaning, while timber windows need oiling and repainting at regular intervals.

Assuming you compare windows of the same frame material, casement windows are the most affordable option. Sash windows and tilt and turn windows have intermediate prices, while bow windows and bay windows are generally the most expensive.

Casement Window Costs

Casement windows are characterised by their simple design, which also means they are the most affordable. They have hinges on one side and an operating level on the other side, and they open outwards towards the hinge just like a door. According to the FMB, the following are good average casement window costs:

Average Casement Window Costs:

Frame Material	600mm x 900mm	900mm x 1,200mm	1,200mm x 1,200mm
uPVC	£150 – £450	£400 – £600	£650 – £900
Aluminium	£500 – £700	£650 – £900	£750 – £1,100
Timber	£800 – £1,050	£1,200 – £1,400	£1,350 – £1,600

uPVC window frames are the lowest cost, but they need a replacement in around 20-30 years. Aluminium windows have higher prices, but they can last for over 40 years. Timber windows are the most expensive, but modern units have a lifespan of over 60 years.

Casement windows are simple and affordable, but you must consider their space requirements. They cannot be used in places where an outward opening window poses a safety risk, or when there is not enough space to open them.

Sash Window Costs

Sash windows have movable glass panels that open by sliding vertically or horizontally along their frames. These windows can be classified into several subtypes:

• Single-hung and double-hung sash windows, which open vertically.
• Sliding sash windows, which open horizontally.

Sash windows have been used since the 17th century, but they are also suitable for many contemporary home designs. The following table summarises the prices per window, depending on their size and frame material:

Average Sash Window Costs:

Frame Material	600mm x 900mm	900mm x 1,200mm	1,200mm x 1,200mm
uPVC	£580	£750 – £850	£935
Aluminium	£700 – £1,200	£1,300 or more	£1,500 or more
Timber	£1,300	£1,900 or more	£2,200 or more

The main advantage of sash windows is being able to open without extending beyond their frames. This makes them suitable for locations where casement windows opening outward create a safety risk, or when there is simply not enough space.

Bay Window Costs

Bay windows are actually an array of three or more windows, joined at an angle to create a shape that projects outward from the walls of a building. The shape of these windows results in an indoor recessed area or bay, hence their name.

• The central sections of bay windows are normally parallel to the wall where they are installed.
• The lateral sections are called flankers, and they are installed at an angle with respect to the central sections.
• The individual units that compose a bay window can be either casement windows or sash windows.
• Thanks to their shape and size, bay windows provide a wide outdoor view and plenty of natural lighting.

Since bay windows are composed of several smaller windows, they are large and expensive. The following are some typical prices for uPVC bay windows according to the Federation of Master Builders:

Average uPVC Bay Window Costs:

Number of Panels	Window Size	Cost Range
3	2,400 – 3,000 mm wide1,200 – 1,500 mm tall	£1,000 – £1,400
4	3,000 – 3,600 mm wide1,200 – 1,500 mm tall	£1,500 – £1,800
5	3,600 – 4,000 mm wide1,200 – 1,500 mm tall	£1,900 – £2,400

Keep in mind that bay windows require outdoor space, since they extend beyond the wall.

Bow Window Costs

Bow windows are composed of many smaller units, just like bay windows. However, while bay windows have a frontal unit with flankers at an angle, a bow window is arranged in a semicircular shape or “bow”.

• Bow windows offer a wide outdoor view and abundant natural lighting, thanks to their dimensions.
• However, they also need outdoor space since they extend beyond your walls.

Bow windows are expensive, since they are composed of multiple sections. Here are some typical price ranges reported by the FMB:

Average uPVC Bow Window Costs:

Number of Panels	Window Size	Cost Range
3	2,400 – 3,000 mm wide1,200 – 1,500 mm tall	£1,100 – £1,400
4	3,000 – 3,600 mm wide1,200 – 1,500 mm tall	£1,500 – £1,800
5	3,600 – 4,000 mm wide1,200 – 1,500 mm tall	£1,900 – £2,300

As you can see, bow windows and bay windows have very similar prices.

Tilt and Turn Windows

These windows have a versatile mechanism that is capable of opening in two ways. They can swing outwards from a hinged side just like casement windows, but they are also capable of tilting inwards.

The pivot point when tilting inwards may be located at the top, middle or bottom of the window frame – depending on how the unit is designed. This function is very useful when an outward opening window poses a threat at certain times of the day. For example, they can be tilted inwards when children are running outside.

The FMB provides the following price for uPVC tilt and turn windows:

• 800mm x 800mm = £450 – £500
• 1,000mm x 1,000mm = £500 – £550
• 1,200mm x 1,200mm = £550 – £600

Buying Double Glazed Windows Tips

Double glazed windows offer energy efficiency and improved comfort, but keep in mind that their payback period can exceed 20 years.

• According to the FMB, you can expect to pay around £4,500 for double glazed window upgrade costs in a three-bedroom property, with installation prices included.
• If you save £150 – £180 in annual energy costs, the payback period would range from 25 to 30 years.

In general, double glazing is cost-effective if you plan to stay in the same home for a long time. Double glazed windows are also recommended for new constructions, where they can achieve a shorter payback period:

• In existing homes, an upgrade to double glazing means replacing your current windows, which have already been paid for.
• In new constructions, windows represent an expense you must assume anyway. In this case, double glazing only represents a cost increase with respect to the baseline.

Purchasing high-quality windows is important, but getting a professional installation is also critical. You should look for a window installation company with the following accreditations:

• FENSA, which ensures that their installations are compliant with your Council’s building regulations.
• TrustMark, which is a UK Government Endorsed Quality Scheme.

You should compare quotes from several window installers to make sure you are getting the best possible deal. Keep in mind that an accurate window upgrade quote is only possible after a site inspection. You should be wary of high-pressure sales tactics and online offers with no prior assessment. 

Make sure you conduct a background check of all the companies offering double glazed windows and ask about their warranty conditions. Here are some typical warranty terms you can expect when purchasing double glazed windows:

Warranty	Length
Hardware (frames, handles, sashes, etc.)	10 years
Workmanship	5-10 years
Sealing	10 years
Stain and paint finishes	5-8 years

Installing double glazed windows on your own is possible, but not recommended. A professional window installation ensures airtightness and warranty coverage.