‘Deemed to Satisfy’ (DTS) refers to a set of prescriptive provisions within the National Construction Code (NCC) that provide compliance pathways for building and construction projects. These provisions are designed to ensure that building designs and construction practices meet the minimum performance requirements set out in the NCC without the need for extra documentation. Read on to discover the answer to the question ‘What is Deemed to Satisfy?’ in the context of energy efficiency and the 7 Stars standard.
National Construction Code (NCC) and Deemed to Satisfy (DTS) Provisions
The NCC is the main set of technical standards and guidelines for Australia’s construction and building industry. It consists of the Building Code of Australia (BCA) for building work and the Plumbing Code of Australia (PCA) for plumbing and drainage work. In NCC 2022 specific DTS provisions were developed to achieve alignment between the NCC and the Nationwide House Energy Rating Scheme (NatHERS) 7 Stars standard, aimed at achieving minimum energy efficiency standards for Class 1a buildings, including R-value requirements for insulation. The DTS provisions outline the methods, materials, design details and construction practices that are considered to meet the NCC’s performance requirements. Builders and designers can follow these ‘pre-approved’ solutions to ensure compliance.
Key Features of DTS Provisions
- Defined Approach: DTS provisions provide detailed and specific instructions, making it easier for builders and designers to understand what is required.
- Standardisation: Using DTS provisions promotes consistency and standardisation across the construction industry, reducing variability and supporting quality.
- Simplified Requirements: DTS provides specific minimum requirements, in turn making it possible to bypass the potentially more complex process of developing and justifying alternative solutions, known as Performance Solutions.
- Ultimate aim: To improve the energy efficiency of buildings, saving the occupants money, increasing energy efficiency and reducing carbon emissions.
DTS Options
There are two different approaches that can be taken:
Option 1: Energy Rating
Under this pathway, each component of the construction undergoes evaluation using NatHERS-accredited energy use simulation software. This software simulates the energy demands for both heating and cooling of each liveable space within the residence to a comfortable level throughout each hour of every day across the entire year. It looks at a wide range of different factors, including regional climate conditions, building orientation, natural ventilation patterns, construction materials, roof colour and more. For instance, in colder climates, recommendations might favour darker-coloured roofing materials to optimise energy ratings.
This detailed approach provides an accurate and tailored picture of the best ways to limit energy demand and is suitable for even the most complex dwellings. It provides a high level of flexibility to builders, allowing them to offset the impact of specific design decisions and still achieve the desired levels of overall performance.
Option 2: Elemental Provisions
This methodology involves a strict adherence to minimum standards for each element, so a detailed examination of each individual building component is required to ensure compliance. Critical aspects include achieving the minimum added or total R-Value of roofs, walls and, occasionally, floors in accordance with AS/NZS 4859.1 and AS/NZS 4859.2 standards, alongside verification that glazing and ventilation systems meet regulatory provisions.
In some respects this appears to be a more straightforward approach, however following the Elemental Provisions route can be restrictive, and limits the potential to optimise overall building performance by balancing higher and lower performing components, as facilitated by the Energy Rating approach. These are some of the challenges:
- The standardised nature of DTS provisions can result in over- or under-specifying insulation and other energy efficiency measures for certain buildings, resulting in inefficiencies and unnecessary costs, or insufficient energy performance.
- Generic DTS provisions may not account for specific-site conditions such as microclimates, varying solar exposure and building orientations that could influence energy performance.
- The ‘one-size-fits-all’ approachmeans that provisions don’t tailor energy efficiency measures to the specific needs of the building or its occupants, potentially resulting in sub-optimal outcomes.
- DTS provisions may not fully address issues such as thermal bridging, where heat bypasses insulation through structural elements. This can reduce the insulation’s overall effectiveness.
- There can be a performance gap between what’s expected based on DTS compliance and the actual performance of the building, due to variable factors such as installation quality.
- DTS provisions focus on individual elements rather than a holistic assessment of the building’s overall energy performance, which can result in a building that meets individual criteria but performs poorly as a whole.
Deemed to Satisfy and the 7 Stars standard
The NCC references the Nationwide House Energy Rating Scheme (NatHERS) for assessing and verifying the energy efficiency of residential buildings. NatHERS measures the thermal performance of residential buildings, rating them from zero to ten stars to indicate how much heating or cooling is needed to maintain comfortable living conditions. Meeting the 7 Stars standard means the building is designed to the current minimum standard for energy efficiency and will require some mechanical heating or cooling.
DTS provisions in the NCC can support the 7 Stars standard in the following ways:
- Energy Efficiency Requirements: DTS provisions outline specific construction practices, materials and design details that ensure a minimum level of energy performance.
- DTS NatHERS: While DTS Elemental Provisions deliver a set pathway to compliance with the NCC, achieving a particular NatHERS star rating, such as 7 Stars, may involve a more flexible DTS approach, allowing for offsetting of R-values between different elements and using the energy rating option to model the best combination of factors to meet the requirements.
- Design Strategies for Energy Efficiency: Using higher insulation levels than those specified in DTS Elemental provisions can help achieve better thermal performance, and can offer a straightforward way to help meet the 7 Star requirements. Design strategies will vary depending on the climate zone.
The NCC Housing Energy Efficiency Handbook provides useful advice and guidance to help designers and builders understand and comply with current requirements based on NCC 2022.
When aiming for a 7 Star NatHERS rating and weighing up the pros and cons of DTS Elemental Provisions versus Energy Ratings, Kingspan’s recommendation is to use Energy Ratings approach as it provides greater flexibility in the design and potential for cost saving. In practice, this is often the easier approach for builders to reach the desired level of energy efficiency and thermal comfort, thanks to the ability to take a tailored approach and make use of NatHERS software.
