NCC 2019: Are You Ready For Change?
For the uninitiated, Australia’s NCC Section J – Energy Efficiency, forms the energy efficiency bedrock for commercial and residential buildings. Mandatory in design yet largely ignored in the built form, Section J remains the default go to compliance benchmark for the vast majority of buildings across this lucky landmass.
Sad but true, it enforces what should be considered as a very low benchmark for energy efficiency in buildings, if we continue to compare ourselves to other developed construction markets with the same access to wealth and expertise.
While 2010 introduced key uplifts in performance requirements, encouraging many parts of our industry to respond with higher performing building fabric solutions, laggards have remained as a more typical component of project aspirations forcing a significant ‘performance gap’ between design and construction.
Next month (20th April, 2018), our design and construction market will have the opportunity to contribute to the proposed change to Section J via the NCC 2019 Public Comment Draft. Resulting from major research and delivered by the Australian Building Construction Board (ABCB), the forthcoming proposed changes are aiming to:
· deliver a projected energy efficiency increase of 40% to the Australian building stock while contributing to a reduction in GHG emissions to 26-28 % on 2005 levels by 2030;
· provide flexibility by expanding on the current compliance options to include NABERS Energy & Green Star as Verification methodologies;
· simplify the Deemed-to-Satisfy (DTS) pathway and encourage performance solutions (JV3, and others).
With such awesome goals, promising to bring Australia’s building stock back in line with meaningful global comparison, these proposed changes are needed, numerous and not for the faint hearted. With so many proposed changes, creating a plethora of documents that few will have time for, I fear they are defaulted never to be read!
In an attempt to drive support for these important changes, I have taken on myself (with help from a few awesome people) to hopefully make it a more digestible process by simplifying the numbers so they can be understood by all and not just the geeks and pen pushers.
Part1: The Battle for Aesthetics
Put simply, commercial and multi-residential buildings have too much glass, typically as high as 70 or 80% window-to-wall ratio (WWR). It’s the elephant in the room and if the intent is to improve performance and comfort, it should not be avoided. Frames of highly conductive aluminium are typically chosen for speed, cost and to maximise floor area against minimum performance requirements. I’m not suggesting it will be easy but this needs to change and is key to the projected 40% target. Now for the technical bit ….
As things stand, building fabric and glazing mandatory provisions will be adjusted under Part J1.5 Wall Glazing Construction. If we are designing multi-residential, schools, aged-care facilities, retail, warehouses or offices in cold to tropical climates, we will see a reduction in glazed area via the combination of two key factors:
- Total System U-value of glazing and walls, not just the glazing.
- A ‘façade solar admittance’ value to account for the fraction of incident irradiance on externally facing “wall-glazing”
Both factors will have a significant impact to design, construction and procurement that is arguably not yet understood.
System U-values - nothing new here right?
The metric of System U-values is not new for glazing systems. However, the new DTS approach aims to incorporate walls into the equation and set minimum R-value backstops for wall performance via a Total System U-value.
Below I have presented a graph to illustrate the System U-value requirement for vision area glazing based on the proposed Total System U-value (glazing and wall) requirement in all Building Classes and Climate Zones. Using a typical R-value of 2.8 m2K/W for the walls, the graph illustrates the requirement for better glazing as we increase our glazing window to wall ratio from 20 – 90%. Click here for an interactive chart, its far cooler!
The purple line shows what I have determined as an ‘Average Thermally Broken Systems’, with a System U-value of 2.8 Wm2.K. What is immediately evident is that the new provisions mandate thermally broken systems in each Building Class and Climate zone if current glazing rations are maintained.
Great news for fabric performance in some climates but highly questionable in terms of procurement, and I don’t simply mean cost. With values as low 1.6 W/m2.K for a 60% WWR in hotels, student accommodation, heathcare (wards) and agedcare within Climates 1/3/4/6/7 (click on the green line), these numbers don’t represent values that can be achieved today without importing from overseas. Indeed, they seem to be assuming PVC frames, which would have incredible resistance from industry in terms of design, installation and supply.
While this scenario looks far more reasonable for hotels, offices, retail, laboratories, schools and healthcare (general) (blue line), where thermally broken frames are mandated if you have glazing ratios > 65%, it will be a challenge in warmer climates that have little exposure to better performing glass and frame options.
Simply put, the new benchmark for performance is high and represents a significant shift that is largely unachievable today. They encourage designs that have a maximum WWR between 30 – 60%, where they should be and more representative of high performance design, but are seemingly driven from a complete disconnection to industry norms and performance realities.
System SHGC - Our buildings are about to get darker!
Unlike today’s Section J provisions, where System SHGC are used to determine the frame and glass fraction of incident solar radiation through a window, 2019 takes on an unusual approach of introducing a new metric with two options for compliance, the Façade Solar Admittance (FSA) value.
FSA aims to account for the System SHGC, external shading and WWR to provide 2 methods for compliance. One that assesses each orientation and level independently and the other that combines all orientations and levels. As per the Total System U-value, the point of interest here is the impact on the glazing requirement as a result of this new approach.
Below I have created a graph to illustrate the System SHGC requirements for vision area glazing based on FSA Method 1, for all Building Classes and Climate Zones. Method 2 will be ignored for now as it will blow out my word count. Again, a 20 – 90% WWR has been used with options for no shading and 1.2 meter shading (horizontal). Again, link here for something more fun!
The purple and blue line approximate the typical System SHGC for commercial (0.25) and multi-residential (0.45) buildings, respectively. Without shading, we can see the lines drop below typical System SHGC values once we get past 50% WWR. After 70%, values exceeding SHGC’s of 0.20 are required in all Building Classes and Climate Zones, resulting in very dark glazing and low VLT values.
Click over to the 1.2 Meter Shading Scenario, and we can see that the System SHGCs relax, allowing slightly lighter glass as a result of the assumed solar control of the shading device. While this makes sense, the System SHGC values including shading remain very low in many cases and continue to challenge the ability for people to see out!!
So what can we expect?
So, in the Battle for Aesthetics, what can we expect? It seems clear that the intent of the provisions discussed above that three key factors are true:
1. We are going to need to reduce our glazing ratios and these are fundamental to improving our buildings energy efficiency performance.
2. Regardless of economic projections, fabric cost uplifts are going to be occurred in buildings with high WWR due to a greater focus on thermally broken frames across most Building Classes and Climate Zones. In cases where performance requirements exceed 1.8 W/m2.K, DTS values are unachievable and should not be introduced as a DTS provision. While this will drive the uptake of Performance Solutions, it also stands to continue the gamification of compliance modelling!
3. The classic battle between solar and daylight is back on the table. The demand for lower SHGC will drive down both the availability of suitable glass products but also compete with the provision of daylight. If we are designing buildings greater than 50% WWR, we will need to introduce darker glass or try to offset it by shading.
Don’t forget the 20th April, 2018 deadline… and don’t take my word for it. It is time to debate the future of minimum performance design which is fundamental to our industry and future. Drop me a line to discuss or meet up for a coffee. The clock is ticking!!