Structural Glazing

What to Consider When Specifying an Oriel Window

An Oriel Window is a popular structural glass window solution for architects and designers looking to create a 3D window design that protrudes from the face of the building. The window design is a structural glass construction made from frameless elements of high specification glass that is sealed together without any framework being required using structural grade silicone.

As this is a structural glass design IQ would design and detail all construction details once an order is placed but what should you consider at the specification stage?


The Size of the Oriel Window

Oriel Windows are installations of structural glass and therefore have no maximum or minimum size. However, there are some parameters that you can keep in mind to ensure that your Oriel Window is cost effective.

The biggest piece of glass produced in the UK is 6m x 3m. If you would like to integrate single panes of glass into your Oriel Window that are larger than that they will need to be sourced from overseas toughening processors. This obviously then adds significant cost and lead time to the glass installation. It is for this reason that most Oriel Window designs would be created using glass panes under 6m x 3m.

An additional size factor to consider is ‘Oversized Glazing’ guidelines. Any piece of glass that is over 2.4m in both dimensions (height AND width), as well as a single pane that is longer than 4m, is oversized. Units of glass that are ‘Oversized’ are more difficult to source and are more difficult to transport to site. This can also add more cost to a project. You can design around the ‘Oversized Glass’ guidelines by keeping at least one dimension of each glass unit under 2.4m.

For example:

The height of this structural glass window was over 3m and the overall face width was over 2.4. If this front face was installed as one single unit of double glazed the glass unit used would have been ‘Oversized’. Instead, the architects (in consultation with IQ Glass) chose to split the face glass and use two frameless panes of structural glass to create the front element which reduced the glazing cost by approximately 30%.

Oriel Window

What Glass Specification Should be Used?

The IQ Glass team will advise you on the glass specification needed to create your bespoke Oriel Window design. To do this we will look at aspects of the installation such as the size of the vertical panes of glass, the weight of the glass roof they will be supporting and the wind load of the project.

In order to create a completely frameless look, the vertical panes of glass will require a strengthening interlayer to the inner pane. This increases the strength of the glass unit so that no steel supports are required to support the roof glazing.

Most Oriel Windows will have double glazing as standard however single glazing can be used if thermal insulation is not a factor. Opposingly, you could ask for triple glazing if improved thermal performance is required.

The glass roof of the Oriel Window can be fully supported by the vertical glass in most designs. The inner pane of the roof element should be toughened laminated glass for overhead safety. On our Oriel Window designs, we use a roof panel that is stepped on the sides. This glass step is 50mm as standard but can be altered on request. The purpose of this is to create a protected seal as well as an adequate edge for water runoff which stops water from dribbling down the vertical surface of the window.


Are Additional Supports Required?

Additional supports (such as glass beams and fins or steel sections) may be needed to be integrated into the structural glass design under some circumstances. These include, but are not limited to:

  • Oriel Windows that include opening elements, such as framed windows or roof vents
  • Oriel Windows that are made from split glass panes
  • Oriel Windows that include a glass roof made from multiple panes

In these instances, we will advise you that additional supports will be required to create your Oriel Window design. If this is not wanted we will be able to advise you on the changes that can be made to the glass installation in order to remove the need for additional supports.

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What Thermal Performance do you need?

As mentioned above, we use double glazing as standard in our Oriel Window designs. The double glazing units we use are highly insulating and include a low e coating and argon gas filling as standard. The typical Ug value of our double glazed units is 1.0W/m2K. If you require a better thermal performance than this then you could consider triple glazing.

The overall Uw value of a structural glass installation has to be calculated for each project.

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What Solar Control Methods are Required?

If an Oriel Window is very large, or South facing, you may need to consider the solar control of the installation. If the structural glass install is subjected to a large amount of sunlight it can cause overheating internally, known as Solar Gain.

This can be counteracted by including elements of solar control into the glass design. The easiest way to do this is with the inclusion of a Solar Control Coating to the glass specification. These transparent coatings are designed to reflect radiant heat away from the internal of a space, thus reducing Solar Gain. We can offer a wide variety of Solar Control Coatings dependant on the performance required and the appearance you want from the glazing.

Alternatively, external or internal blinds could be integrated into the glass structure in some way.


Do You Want to Include Opening Elements into the Window?

If you want an element of your Oriel Window to open (for ventilation for example) then it is possible to integrate a framed window into the structural glass design. However, the inclusion of an opening element such as this will require steel supports to be included in the glass structure. This is often not the appearance that architects are looking for and is therefore not done very often.

If you do wish to have an opening window in the Oriel design then you can select any of our casement window options. These include minimal aluminium framed windows as well as a range of thermally broken steel window systems.

Oriel Window

What is the Base Structure we are Installing Onto?

An Oriel Window has a solid base structure which is designed and constructed by others, most often the builder or contractor on the project. Our Oriel Box Windows require a base of either steel or concrete to fix directly into.

You do need to think about how this base structure will be finished. Many architects will choose to use back painted glass to cover the base structure. This is designed to sit flush with the vertical glass panes of the window and creates a sleek, all-glass design.

Alternatively, an aluminium or architectural metal pressing can be used for a different aesthetic.

Oriel Windows from IQ is a bespoke design solution and we work hard to ensure that our Oriel Window designs meet both the design and performance criteria for each project. If you have any questions about your own Oriel Window design or installation please contact the team on 01494 722 880 or email for more advice.