In the UK, there are several types of double-glazing options available for windows and doors. These options vary in terms of their construction, energy efficiency, noise reduction, and cost. We outline some of the common types of double glazing available as well as the different styles of double glazing currently available on the market. There is ample choice when it comes to double glazing styles and types, so you will be sure to find something that complements your property, your needs, and your budget, perfectly.

Double glazing window types


Double Glazed Units (DGUs)

DGUs consist of two glass panes separated by a gap filled with air or a gas, such as argon or krypton. They are the most basic form of double glazing and provide improved insulation compared to single glazing.


Low-E glass

Low-emissivity (Low-E) glass has a special coating that helps to reflect heat back into the room, reducing heat loss and improving energy efficiency. It also allows natural light to enter while minimising harmful UV radiation.


Acoustic double glazing

This type of double glazing is designed to reduce noise transmission, making it suitable for properties located in noisy areas or near busy roads. Acoustic double glazing typically incorporates thicker glass panes and a wider air gap to enhance sound insulation.


Triple glazing

Triple glazing consists of three glass panes with two insulating gaps, providing an extra layer of insulation compared to double glazing. It offers improved thermal efficiency and noise reduction, but it can be more expensive than standard double glazing.


Secondary glazing

Unlike the previous options, secondary glazing involves adding an additional pane of glass to the existing window rather than replacing the whole unit. It provides some of the benefits of double glazing, such as improved insulation and noise reduction, and can be a cost-effective solution for older properties or listed buildings.


Slimline double glazing

Slimline double glazing is designed for properties with narrow window frames or those seeking a more aesthetic appearance. It uses thinner glass panes and narrower air gaps while still providing effective insulation.


Self-cleaning glass

This type of double glazing has a special coating that uses sunlight to break down and wash away dirt and grime, reducing the need for manual cleaning.


Laminated or toughened glass

These types of glass are more resistant to breakage and provide added security. Laminated glass consists of a layer of plastic between two glass panes, while toughened glass undergoes a heating and rapid cooling process to increase its strength.

It’s worth noting that different manufacturers may have their own branding and variations within these categories. When choosing double glazing, it’s important to consider factors such as energy efficiency, security features, warranty, and installation quality to ensure the best performance and value for your specific requirements.


Vacuum insulated glazing

A premium glass option that offers the ultimate in insulation for buildings. It consists of two glass panes with a very thin gap in between them. The gap is sealed, and the air inside is completely removed to create a vacuum.

The vacuum helps prevent the transfer of heat or cold between the two glass panes as there is no air to conduct the heat, making it much harder for heat to move from one pane to the other.

The team at Parsons Joinery are approved installers of Fineo vacuum insulated glass which offers insulative benefits greater than triple glazing but within a form factor as slim as single glazing. It is a superb option for listed and period properties as it can be retrofitted into the existing window frames if needed. To date, we have not had a planning application for this glazing solution denied. Full benefits of Fineo vacuum glazing can be found here.

Double glazing window styles

There are various double-glazing styles available to suit different architectural designs and personal preferences. Here are some popular double-glazing styles:


Casement windows

Casement windows are hinged on one side and open outwards. They are popular for their versatility and can be designed to fit various property styles. Casement windows can be single or multiple panes and are available in different configurations, such as top-hung or side-hung. With the right glass and frame options, excellence in energy efficiency can be achieved. Plus, casement windows are easy to clean and maintain and offer good ventilation control.


Sash windows

Sash windows are a traditional style commonly found in older properties. They consist of two vertically sliding sashes, allowing for controlled ventilation. Double glazing can be incorporated into sash windows to improve energy efficiency while preserving the elegant aesthetic appeal.


Georgian bar

Georgian bar windows are another popular choice when it comes to older properties due to their ability to give the appearance of having multiple small windowpanes in each window unit to replicate the window style common of the Georgian era. True Georgian bar windows are made up of six separate panes of glass visible on both the inside and outside of the sashes and run throughout the whole sash (commonly termed real-dividing bars within the industry).

uPVC window suppliers have their own version of the six-pane design, whereby they add bars to the double-glazing, and they are sealed within the Georgian bar window unit.

Astragal bars (referred to as ‘applied glazing bars’ in timber frame manufacture) describes timber bars that are planted on to the window glazing both on the inside and the outside of the pane to create the illusion of six separate panes of glass, when in fact, there is just one pane used.


Bay and bow windows

Bay and bow windows are designed to create a protruding, curved, visually appealing structure that extends outward from the main wall of a building. These windows enhance the interior space by adding depth and dimension to the room, provide panoramic views, and allow more natural light to enter the space. Double glazing can be installed within the bay or bow structure to maintain energy efficiency.


Tilt and turn windows

Tilt and turn windows offer versatility in terms of ventilation options. They can be opened inwards from the top for secure ventilation or fully opened inwards for easy cleaning and emergency exit purposes. Tilt and turn windows often feature multiple locking points for enhanced security.


French windows and doors

French windows, also known as French doors, are double doors that open outwards or inwards. They typically feature large glass panels to maximise light entry and offer an elegant and classic design. Double glazing can be incorporated within French windows and doors to improve insulation and energy efficiency.


Sliding patio doors

Sliding patio doors are a popular choice for connecting indoor and outdoor spaces. They feature large glass panels that slide horizontally, providing ample, unobstructed views and easy access to the patio or garden. Double glazing can be incorporated into sliding patio doors to enhance insulation and reduce heat loss.


Bi-fold doors

Bi-fold doors consist of multiple panels that fold and slide to create a wide opening. They are an excellent choice for maximising space and creating a seamless transition between indoor and outdoor areas. Bi-fold doors often feature large glass panels, allowing plenty of natural light into the room. Double glazing is commonly used in bi-fold doors to improve energy efficiency.


Conservatories and orangeries

Conservatories and orangeries are popular options for adding extra living space and bringing the outdoors inside. These structures are predominantly made of glass and incorporate double glazing to ensure energy efficiency and thermal insulation.

When choosing a style, it’s worth taking time to consider factors such as functionality, aesthetics, security, and energy efficiency to meet your requirements and complement your property’s design – particularly if you own a period or listed property.

In summary:

Generally, glazing offers several benefits regardless of the style you choose:


  • Enhanced thermal insulation, reducing heat loss, and saving energy.
  • Improved sound insulation, reducing noise from outside.
  • Increased security and safety due to the presence of multiple layers of glass.
  • Reduced condensation on the inner surface of windows.
  • Potential for lower energy bills and increased energy efficiency rating.
  • Potential to increase the value and kerb appeal of your property.

Double glazing frames

When it comes to frame options for double glazing, there are several materials commonly used. Here are some of the most popular choices:

UPVC windows

uPVC (Unplasticized Polyvinyl Chloride)

UPVC frames are widely used due their durability, minimal maintenance requirements, and excellent insulation properties. They are available in a variety of colours and finishes, and they can be easily customised to fit different window styles.



Aluminium frames are known for their strength and durability. They are lightweight, only require modest maintenance, and can be easily customised. However, aluminium is a good conductor of heat, so it is important to ensure that the frames have thermal breaks to improve energy efficiency.



Wooden frames provide a classic and natural look that many homeowners prefer. Wood is a good insulator and offers a traditional aesthetic appeal. Choosing the right wood for your project is important. The difference between hardwood and softwood is straightforward, but you will need to consider which wood would be best suited for your project.

At Parsons Joinery, we predominantly use five types of wood – European Oak, Utile and Sapele, Iroko, Redwood, and Accoya. Find out more about all the wood species we work with and why we rate them so highly. We treat all our wooden windows and doors with wood preservatives and protective films of paint/varnish/sealer to ensure that all surfaces are completely sealed, aiming to avoid the excess water being trapped below them.



Composite frames are made from a combination of materials, typically a mix of wood and uPVC or aluminium. These frames offer the benefits of both materials, providing good insulation, durability, and low maintenance.

Frame colours

Once your frames and window styles are chosen, you will need to consider colours. There are options for every taste and style of home. At Parsons Joinery, all our paints are sprayed for a seamless, smooth finish. As standard we include white gloss/white satin. However, if you have a specific frame colour in mind then we can colour match to any Dulux, Farrow & Ball, Little Greene, Fired Earth, or other paint brands. You can even have a different internal frame colour to the external frame colour as all our products are completely bespoke.
Many people choose to install new outside doors as part of the process of getting new windows. The wonderful thing about doing this is that you can match everything in the same style so that your home looks coordinated and uniform.
We make everything bespoke therefore, we can match your door colour and glazing with your window frames, or craft something completely unique.

Got a question about double-glazed windows or doors? Contact Parsons Joinery on 01273 814870 or email – we’d love to chat.