Confused what the new NCC 2019 Section J requirements mean for your 2020 commercial construction projects? Here’s a rundown of what you need to know about facade, glazing and wall assembly performance.
The 2019 National Construction Code didn’t just tweak the requirements for commercial buildings under the Section J energy efficiency specifications—it re-wrote them all together.
The performance of the building envelope, which includes the walls, windows, roof and foundation, forms the primary thermal barrier between the interior and exterior environments, is now at the centre of compliance requirements.
Compliance Changes in Design and Construction
One of the big changes from a design and construction perspective is that current glazed curtain wall assemblies may no longer be suitable.
Darren O’Dea, director of Fabric First building physics consultancy and co-founder of Speckel, a building envelope design platform, told Jobsite that the new NCC Vol 1 is far less forgiving when it comes to what will or will not “get over the line.”
Previous iterations of the NCC allowed a certain degree of flexibility in meeting requirements for façade performance, he explains.
The 2019 NCC energy efficiency provisions, fully in effect from May 2020, require the full assembly of glazing, spandrels, fenestration and other parts to be assessed. Glazing is no longer considered separately in terms of its thermal performance.
The new NCC Vol 1 is far less forgiving when it comes to what will or will not “get over the line.”
For projects following a performance compliance pathway, the entire design team—architect, engineers, ESD and façade consultant—must be across the changes. Projects following the Deemed-to-Satisfy pathway will be more rigorous and demanding in order to achieve compliance.
O’Dea says the new compliance pathway is “more onerous and thought through” and has “fewer grey areas.”
New Rule Aims to Improve Thermal Performance
The thinking behind the change is enhancing building envelopes in terms of thermal performance as it is one of the “lowest hanging fruit” in regard to improving energy efficiency. The better the façade performs to regulate heat or cold coming in or passing out of a building, the less energy is required to keep occupants comfortable.
According to O’Dea, it is also seen as one of the easier things for the construction supply chain to commit to. The key will be committing to it now, to ensure all the right factors are considered at the points of tendering, detailed design, specification, procurement and delivery.
There are two main ways most commercial projects procure and deliver facades. The first one uses a unitised approach for curtain walls, with most products obtained from suppliers in China and other parts of South-East Asia. For these systems, O’Dea says specifiers need to consider the requirement for larger spandrel up to 800mm from floor height. They should also ensure glazing framing is thermally broken.
The second type of façade is the stick-built style, and the new requirements will put greater focus on the fenestration solution as a whole. The design and specifications for the façade assembly are considered as a whole unit rather than just a kit of individual parts.
O’Dea noted the use of WERS [Window Energy Rating System] values will no longer be acceptable as a commercial solution. Instead, ratings and values considering subframing thermal bridging and the installed window size will be required for the calculations.
Closer Focus on Role of Framing
NCC 2019 pays close attention to the role of framing in either supporting or compromising thermal performance. Standard aluminium framing has high conductivity for heat or cold. Therefore, it has a major impact on overall façade performance despite being a small element by area.
Thermally-broken aluminium framing can add to costs. However, projects following a performance pathway can utilise other systems, such as engineered timber with compliant fire protection, accroding to O’Dea.
Regions Affected Most by New Requirements
While the Melbourne market has already matured in delivering high-performance facades, the new requirements will be challenging for many builders and specifiers in Perth, Sydney and Brisbane, O’Dea says.
Clients and architects will also need to make some adjustments—the new spandrel requirements may slightly reduce gross floor area and alter the vision area-to-wall ratio.
“I think we will see the rise of more refined strategies around vision area and spandrel area and some smart thinking around that.”
O’Dea says a change of practices will also be required regarding the coordination of trades and some elements of building detailing such as the installation of plasterboard and insulation. The key message is builders and project teams need to start incorporating changes to design, materials and labour requirements in tenders in order to ensure the projects they are contracted to deliver from May 2020 onwards will be compliant.
The Australian Building Codes Board has produced a range of resources to assist including a handbook and a basic calculator. Speckel.io offers a comprehensive platform that enables project designers and specifiers to test actual designs and plans against NCC 2016 and 2019 requirements. They can use it to experiment with a wide range of products available in the market to refine the final façade solution specifications and complete NCC compliance reporting.