The National Construction Code allows for Section J compliance for Commercial buildings using a range of different assessment methods. Two of the most commonly used are the JV3 and Section J Deemed to Satisfy (DTS) methods:
- JV3 – develops a full thermal model of the building and determines the performance of the building against a reference building design.
- DTS – simple comparison of the building design to a benchmark set of minimum standards for the thermal performance of each of the main element of the building (roof, walls, glazing, floors etc.)
It is very common for architects and designers to assume that a complex or large building design can only achieve Section J compliance using the JV3 thermal modelling method – but this is very often not the case.
Significant improvements to the Deemed To Satisfy (DTS) verification method in both NCC 2019 and NCC 2022 mean this is a powerful and versatile tool for achieving Section J compliance in a simpler, quicker and cheaper way – even for large and complex designs.
In our experience JV3 is best suited not so much for complex buildings but for what you might call unusual buildings, or buildings that have a large specific feature or specific requirements. Some examples from recent work with our clients where we recommended JV3 be used:
- A three storey car showroom with full glazing on three and half sides of the building.
- A large shopping centre with ~50% of the conditioned area covered by a skylight over a central atrium.
The unusual features of these buildings are not suited to DTS evaluation, and JV3 or other full modelling software is required.
Many other large or complex buildings, however, achieve energy efficiency compliance using the Section J DTS method. Here are some of the buildings we have recently assessed using the DTS with clients very happy with the results:
- A 12 storey Class 3 NDIS residential tower with full glazing on two sides.
- Large shopping complex.
- 13 buildings of an new high school project, including multi-storey and discipline-specific building designs.
- Many multi-storey office blocks.
JV3 can add unnecessary expense and delays to a project when the DTS methods provides a simple and straightforward path to compliance. A DTS assessment must also be completed for each JV3 (to be used as a ‘reference’ case), so in cases where a JV3 is later determined to be necessary, the value of the DTS is not lost.
Until NCC 2022 the DTS method required sub-slab insulation for slabs on ground for smaller buildings – this was often an impediment to using the DTS method. This requirement has been removed in the latest version of the NCC (2022), in part to enable/encourage use of DTS in more projects.
Since NCC 2019 the DTS method has also allowed trade offs between glazing on different facades of the building. This added level of sophistication in DTS calculations means it is a much more flexible in assessments of complex buildings. You can have one side of a building with a large area of glazing, but this is averaged against other sides with less glazing, reducing the overall glazing specification.
DTS is a quicker, cheaper and simpler method for assessment, and should be the first option considered for assessments. JV3 should be used where there are specific project features or requirements that mean DTS is unsuitable.
We provide free advice to our clients on the likely outcomes of a DTS assessment vs the JV3 assessment prior to starting the assessment – contact us today with your project to see how we can help.