True vs Applied Glazing Bars in Steel Windows and Doors

A key design feature of many steel or architectural metal windows and doors is the inclusion of glazing bars into the glass face. These elements of profile crisscross over the glass face and create more of a design feature for glass elements.

Glazing bars within the glass structure were a necessity for older windows as glass engineering was in its infancy. Large window or door installations relied on the inclusion of additional elements of frame to provide the strength to the glass element.

Now, glazing bars are seen as part of the design of steel windows and doors and mimic that industrial design so often found in warehouses, Bauhaus architecture and loft style apartments.

When looking to include glazing bars into your modern steel framing system you have two choices; True or Applied glazing bars.

What is a True Glazing Bar?

A true glazing bar is a more traditional option for including glazing bars into a steel frame. The glazing bar is a true element of frame that dissects through the depth of the window/door frame and separates glass units.

Glazing bars that are ‘true’ have a dictated profile size depending on the steel window or door system you are using. This ranges from 35mm up to 50mm and will be shown in the standard details of the steel window and door system you are looking at.

When using true glazing bars you also need to take care that you don’t create ‘top heavy’ opening elements. If you have lower level glazing bars the glass units at the head of the door or window will be heavier than those at the bottom. This may cause the door to skew over time.

steel doors with true glazing bars
thermally broken steel patio doors

What is an Applied Glazing Bar?

An applied glazing bar is a glazing bar that is adhered to the surface of the glass unit. The glazing unit is full size, filling the outer framing of the window or door. The glazing bars are then applied to the surface into the chosen pattern and configuration.

If you select an applied glazing bar design you can be very flexible with the pattern of glazing bars you use. This is because the integration of glazing bars into the opening doesn’t effect any structural elements of the door leaf so can be as complex and intricate as you like.

As applied glazing bars are just decorative you can also have much slimmer bars that what can be achieved with true glazing bars. As standard most applied bars would be 25mm but different sizes are very possible.

true vs applied glazing bars infographic

Which Glazing Bar Type Should I Use?

Which glazing bar you should use will differ from project to project. Your glazier will be able to help you determine which glazing bar type will be best for your project and required performance criteria. Below are some of the key considerations in specification.

Considerations for True Glazing Bars

Keep in mind that True Glazing Bars will reduce the overall Uw value (thermal performance) of the glass installation very slightly. This is because the frame is the lowest performing element of the window/door installation. Every time you dissect a very well insulating piece of glass with a lower performing piece of frame it reduces the overall thermal performance.

This reduction in thermal insulation is only slight but if the glass element has many glazing bars in it the overall reduction could be significant for the project targets.

In addition, the choice of True Glazing Bars will result in a higher cost and additional lead time for the steel window or door. This is because of the additional fabrication, man-hours and labour required to integrate a True Glazing Bar into the steel frame.

steel windows and doors to modern house
steel doors with applied glazing bars

Considerations for Applied Glazing Bars

Applied Glazing Bars often offer a more cost-effective option for steel systems, as well as maintaining the thermal performance values and allowing for a more flexible approach to the glazing bar design.

If you do choose Applied Glazing bars you should ensure that dummy spacers bars are used within the glass unit. This is a superfluous spacer bar placed within the gas cavity in the location that the glazing bars will go. When the door/window is installed on site the glazing bars are then applied on top of this both inside and out. This then gives your applied glazing bar design a more authentic appearance as it looks like the frame goes all the way through the glazing.

We don’t recommend Applied Glazing Bars for very large glass units as over large spans it can be difficult to ensure the glazing bar is applied perfectly. Glass units with applied glazing bars have a maximum recommended size of 1300mm wide by 2440mm tall. This ensures we can maintain an extremely high level of finish.

Why Not Decide in Person?

Our Mondrian® Slim door system installed at our showroom in Amersham has both True and Applied glazing bars integrated into the same elevation. This allows architects and their clients to see the visual differences between a true and applied glazing bar option and make their decision based on this.

Both True and Applied Glazing Bars are available with any of the steel systems from IQ®, including our exclusive Mondrian® range of steel windows and doors.

To book your personal consultation at the Courtyard Showroom speak to a member of the team at IQ®. For further information about the Mondrian® steel range or for more advice about glazing bar options just get in touch with the team at IQ®.

steel door showroom

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Rebecca Clayton
Technical Sales
Rebecca is Head of Marketing at the IQ Group and has worked in glazing specification for many years. She has a broad range of technical knowledge about all our glazing products and offers technical advice and guidance to architects for specification. Her easy to digest technical advice is often quoted in magazines and publications. You might also recognise her as one of the IQ Glass CPD presenters.
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