What are the limitations of DTS Energy Compliance?
Section J is a low cost and fast compliance avenue to National Construction Code. At Energy Compliance we always recommend the DTS solution first as it is low cost. However, as it is prescriptive, it is also not flexible, which may pose a challenge to energy compliance. In some cases, achieving compliance to DTS might significantly increase construction costs (i.e. added insulation to the existing slab), or it may be highly undesirable to adopt due to aesthetic limitations. But don’t worry, there are other avenues to help reach a favourable solution, such as utilising the JV3 Performance Solution method.
Though Section J DTS reports providing a fast, simple and straight forward NCC energy efficiency compliance method, they have some potentially significant drawbacks:
- Deemed to Satisfy requirements are very strict and must be followed with no exception. For instance, if for aesthetics reasons, the client wants to have an exposed concrete wall both inside and outside the building, the Deemed to Satisfy requirements would still require insulating every inch of that wall.
- Fully glazed walls typically don’t pass the NCC DTS glazing requirements, or they’ll only pass with triple glazed windows which are cost-prohibitive.
- The DTS methodology only looks at specific building fabric components as individual items and doesn’t consider the holistic performance of the entire building.
- On the grounds of ESD, some councils may ask you to go beyond DTS (e.g. 10% better than the DTS provisions). Therefore, DTS pathway of energy compliance may not be achievable using typical glazing or insulation. In these types of situations, alternative methods of energy compliance are preferred over DTS.
- There are no elemental provisions for Class 2 and Class 4 part of the building, therefore, the only pathway of energy compliance for Class 2 and Class 4 buildings is NatHERS star rating.
- Using BESS tool, you can use DTS elemental pathway for energy efficiency of residential dwellings; Only NatHERS star ratings allocate certain scores for residential dwellings.
What are alternatives to DTS?
Luckily, the NCC offers an alternative Energy Compliance method that considers holistic building performance! This, importantly allows us to consider the interaction between all the different parts of the building fabric, and to improve some parts by assigning alternative, lower-cost DTS thermal performance requirements to the rest of the building.
This alternative type of Energy Compliance method is called a “Performance Solution” and is discussed in the NCC. Verification methods are performance solutions detailed by the NCC. Among these verification methods, JV3 modelling, JV2 Green Star and NABERS are the most promising methods of energy compliance for commercial buildings. JV3 is a Verification Method, which allows demonstrating compliance with the mandatory Performance Requirement JP1 in NCC Volume 1. It can be used instead of the DTS Provisions of Parts J1 to J7.
The JV3 method essentially provides flexibility in how to achieve Energy Compliance and reduce construction costs, whereas the prescriptive DTS Provisions may not work for certain building designs and maybe a higher cost approach.
Also, DTS pathway is not all inclusive. In some cases you don’t have any problem complying to the NCC energy efficiency provisions, however, your council may ask you to present evidence that your spaces are adequately daylit through verification method. if this is the case, then you need to undertake daylight modelling to back up your claim. Results of daylight modelling and DTS for energy efficiency may be contradicting to one another. JV3 modelling uses the same building model the daylight assessment does, therefore, you can save time and cost undertaking JV3 modelling instead of DTS pathway.