Preface: On the Nature of Building Codes and This Analysis

As we delve into the complexities and implications of thermal breaks and thermal bridging mitigation within the framework of NCC 2022, it is essential to acknowledge the foundational basis of our analysis. This article draws upon the current standards and regulations as stipulated in the 2022 edition of the National Construction Code (NCC). It aims to provide a comprehensive understanding of the research conducted by LittleShrub Pty Ltd for the Australian Building Codes Board (ABCB), focusing on the significant strides made in building insulation practices, energy efficiency, and thermal performance enhancement.

However, it is crucial for readers to recognise that building codes are living documents, subject to revisions and updates that reflect new knowledge, technologies, and societal needs. As such, future versions of the NCC may present different requirements or interpretations of thermal breaks and thermal bridging mitigation. Our discussion is rooted in the present, with an eye towards sparking a broader conversation about the evolution of construction practices and the pursuit of sustainability and energy efficiency in building design.

This preface serves not only as an introduction to the subject matter but also as a disclaimer: the insights and recommendations provided herein are based on the NCC 2022 and may not fully align with future iterations of the code. The intent is not to prescribe definitive solutions but to contribute to an ongoing dialogue among professionals in the construction industry, encouraging the exchange of ideas and the exploration of innovative approaches to thermal management in buildings.

We invite readers to engage with the content critically, considering both the current state of the art and the potential for future advancements. By fostering a culture of continuous learning and adaptation, we can collectively advance our goals for more sustainable, efficient, and comfortable living environments.

When to use a Thermal Break

One of the more practical outcomes of the research was to answer the question: When do you need to use a thermal break to satisfy 13.2.5(5)? The time this question became most relevant was when a metal stud frame wall had metal battens fixed to the studs. More specifically, what is the definition of a metal frame? Does this include the metal battens? The research used both grammatical and technical analyses to determine the intent of the clause. The outcome of this analysis demonstrated that the thermal breaks are required both when a wall has a metal frame without battens and when the wall has metal battens. This is then illustrated by the flowchart below

What about the explanatory information of 13.2.5?
There is an explanatory information section in 13.2.5 that states: 'Because of the high thermal conductance of metal, a thermal break is needed when a metal framing member directly connects the external cladding to the internal lining or the internal environment...'. An argument is made by some, that because this explanatory information states 'directly connects', then this means that the metal battens are not included in the definition of a metal frame. However, this a logical fallacy known as denying the antecedent. It is equivalent to stating:

If you are an engineer, then you have a job.
You are not an engineer.
Therefore, you do not have a job.

It's clear to see that this is not a valid argument. The same logic applies to the explanatory information. It demonstrates a specific case where a thermal break is required. This does not mean that this is the only circumstance where a thermal break is required. The full research then uses the demonstrated methodology of AS/NZS 4859.2 to validate this statement. Indeed, the research supports the explanatory information statement, but it also supports the fact that a thermal break is required when a wall with a metal stud has metal battens.


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