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  • Writer's picturePengfei Yang

Section J Energy Report - Calculations

Updated: Aug 24, 2023


Today, we’d like to discuss energy assessments for commercial projects, including part of Class 2 to Class 9 buildings. They can be offices, community centres, and so on. One of the pathways is to assess the building elements using the DTS Provisions of Section J in the National Construction Code (NCC) Volume 1.


Energy Compliant Calculations

The method is to calculate the proposed elemental performance values and compare them with the requirements in each part of Section J. Calculations can be done differently depending on the elements.


Compliant Solutions for Floors

Take floors, for example, will need to satisfy every applicable part of the requirements in J1.6. One is that in Tasmania (Climate Zone 7), a floor without an in-slab heating or cooling system must achieve a Total R-Value with a downward heat flow of 2. The sub-floor and soil R-Value will also be calculated in the Total R-Value calculation. Specification J1.6 will be the reference for the R-Value of sub-floor spaces and soil in contact with a floor. (Yawning yet? Very close to the end now!)


How to Satisfy the Code Requirement

Now, it’s the tricky part. The ratio of the floor area to floor perimeter and wall thickness will determine the floor type and whether the proposed floor meets the minimum R2 requirement. Let’s assume the soil R-Value is 0.8 and the proposed slab with 300mm waffle pods, the Total R-Value of the floor will be: 0.16 (indoor still air) + 0.07 (100mm slab) + 0.63 (300mm pods) + 0.8 (soil) = 1.66. It clearly will not pass the required Total R-Value of 2. If it’s not too late, change the waffle pods slab to slab-on-ground with continuous under-slab insulation can make it to 2.03, and it is a pass. Sometimes it is just that close and maybe can cost a lot to change structural elements.


Start Energy Assessment Early

You must be tired of this blah, blah, boring stuff. Don’t worry! That’s why a professional energy assessor exists. They can work out the behind-the-scene calculations for you on the ‘dark side’ and help you bring your project to the light. The key is the old classic engage early! No matter a residential or commercial.


Energy Assessors Can Help

Speak with your regular assessor if you have one, or we can also help if they are busy. Just contact us and see how we can help.




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