• Fabric First

NCC 2022: NatHERS in a carbon restrained world?

Updated: Aug 12, 2019

2019 has been an exciting year for Australian energy efficiency aficionados. Finally, well by May 2020 anyway, we will start to see a trickle of commercial buildings meeting minimum performance requirements broadly similar to those on International, developed construction markets.  

Once we have played the games, renewed old building permits and worked through the opportunities to game the system, we will be on a construction market where performance expectations and realities will be higher. I cannot wait!

Come 2022, after the most cost sensitive projects complete the race to the bottom and have no way but up, our single glazed, aluminium framed commercial building market will have become largely a thing of the past, perhaps with exception of shopfront glazing. Meanwhile, i suspect 2016 glazing solutions will no doubt have evolved, with product lines changing, new players displacing the old under a better understanding of façade performance.

But what of our residential buildings?

Sure, commercial buildings are important but without considering our new and existing residential buildings, are we only focusing on a thin slice of the wedge, not the real challenge in the built environment? With key findings from most policy documents suggesting Australian's emissions are rising and projected to continue without credible and comprehensive climate and energy policy, is this our last opportunity to buck the trend and make amends?

Sure enough, things may be just about to change, allowing a clearer view of at least part of the national strategic framework that will underpin the Paris Agreement commitment to reduce GHG emissions by 26 – 28% of 2005 levels by 2030. Available just a couple of weeks ago, the ABCB released a glimpse of what residential design and construction practise could look like post 2022. Titled Energy Efficiency: NCC 2022 and beyond, this scoping paper provides a solid look at the initial approach and intent of our future residential buildings and is available for all to comment.

The fundamentals - 2 options and Zero choice

Without digging into every detail, the paper sets forth two NCC provisions, based on a primary goal of achieving ‘a high level of thermal comfort equivalent to 7-star NatHERS’ via ‘whole-of-house’ modelling.

The options then set two annual energy use aspirations, 1) Net Zero Regulated Energy (NZRE) and 2) Moderate, for controlling regulated building services typically covered by NCC requirements. These included space conditioning, heated water systems, lighting and pool and spa pumps, if you are lucky to have such modern luxuries.

Now, there is some good stuff here, potentially great. Anything that aims to control annual energy use is a good thing and an obvious driver for better buildings. NZRE, of course, would need to be supported through onsite renewables to offset annual energy use. While zero regulated energy doesn’t cover all energy use, it covers some big ticket items, as per the definition below:

“NZRE is achieved when the net annual energy use of all the services regulated by the NCC energy efficiency provisions equals zero. Regulated services include space conditioning, heated water systems, lighting and pool and spa pumps. NZRE may be achieved by offsetting the energy use of these services with energy generated by on-site renewables.”

With millions of dwellings now adopting for solar and many coming around to storage as battery prices become more economical or simply justifiable, this could result in a major step forward! While not without its complexities and given the advanced activities on other global markets such as nearly Zero Energy Buildings (nZEB) in Europe, NZRE is an absolute must and should not be subject to any debate.

An area I am perplexed about, however, is the reasoning to continue to prioritise the Nationwide House Energy Rating Scheme (NatHERS) rating system as a measure of performance, if meaningful change is the focus. For those unfamiliar, NatHERS is a star rating system (out of ten) driven by a CSIRO calculation engine that rates the energy efficiency of a residential building to estimate potential heating and cooling energy use. NatHERS also claim to “help make Australian homes more comfortable”.

To date, it is largely ignored by consumers as it provides no real-world reassurance for performance or comfort. Arguably, in its current state, it provides more value as an administration network to retain job security than a value add to the built environment. That does not mean we can't change it though!

Performance in the Stars

With a target of a 7-star NatHERS rating set to be indicative of future building quality, a building fabric backstop is the focus within Energy Efficiency: NCC 2022 and beyond, which makes sense if such a rating guaranteed a high level of performance. More on this later.

However, should we continue to commit to the NatHERS system, surely it is time to overall this comical notion that a rating system should start at a seemingly random number and not represent a clear range of performance increments that is simple to understand for the consumer market.

Today, NatHERS confusingly starts with a legal minimum performance requirement of between 5.5 and 6 stars, climate dependent. Real estate agents proudly state ‘a 6-star building energy efficient home’, either without knowing it is a legal minimum requirement or more likely, without making the effort to understand.

To retain value and clarity with a consumer market that needs further education, we need to commit to a revised NatHERS rating system that is clear, with logical minimum and maximum performance aspirations. Thereafter, make star rating declarations mandatory at a federal level and allow consumers the opportunity to see value for themselves, subject to more comments below. Look to Europe, we can see alphabetical ratings, with an “A” being a top rating and “F” being terrible. Surely this makes more sense than “10” being a top rating, “7” being the legal minimum requirement and “0 – 6” being, well, nothing!

Closing the Performance Gap

While the hundreds that have trained to become NatHERS Accredited Assessor cannot be ignored, all evidence to date suggests that the design outcomes of NatHERS assessments are not associated to building operational performance. In other words, the “performance gap” created through NatHERS design ratings and construction quality is commonplace and if not dealt with, a real impediment to better outcomes and GHG reductions.

This is major issue for all construction, if not the greatest issue for real world building performance. Unless construction detailing is verified by diligent practitioners without any vested interest or connection to the project, NatHERS ratings will remain a dangerously hypothetical exercise of little real world value. There are enough NatHERS Accredited Assessors to partially audit their own work. Supported via Independent verification, there is a major opportunity to upskill the existing cohort of assessors, deliver better buildings and retain a version of the NatHERS status quo.

Thermal Comfort?

Now, this was not supposed to be a NatHERS bashing but this bit drives me a little crazy. There is no association with the thermal comfort of occupants and a NatHERS rating, even a 7-star rating. To allude to a minimum performance requirement being met that has a ‘thermal comfort’ backstop through NatHERS is as truthful and the nonsense flowing from the lying lips of the 45th President of the United States!

At the simplest level, today, in all Australian capital cities, a 7-star NatHERS rating can be designed with single glazing. Yep, single, so called ‘high performance’ low-E glazing. The evidence, NatHERS very own website and it’s ‘7 Star House Plans’. So, in 2022, we could have a rating system that is aligned to meeting the Paris Agreement commitment while ensuring a high level of occupant thermal comfort via single glazing? You might need a lot of solar to offset that shortfall!

Technically, where this comes unstuck is in the detail of providing thermal comfort for occupants based on heating and cooling demand alone. It is not air temperature that provides the best estimation of occupant thermal comfort, it is surface temperatures as they are the primary driver of heat exchange with our bodies through radiant means.

As indicated above, if a 7-star NatHERS rating is possible with single glazing, then it will guarantee discomfort using typical comfort indices during both summer and winter scenarios. Indeed, double glazing is also no guarantee to ensure occupant thermal comfort under high or low exterior conditions and is dependent on the framing system and other factors, so an overhaul of this illusion to comfort needs far more consideration than relying on heating and cooling demand alone.

Detail, Detail, Detail

NatHERS software are all commonly supported by the Chenath calculation engine, an ASHRAE 140 tested thermal performance software developed by the CSIRO. The Chenath engine is critical to enhance theoretical modelling and can do some great things. However, with its current interface options, including FirstRate, Accurate and BersPro, it is fundamentally limiting the user through the understandable intent of being able to compare apples with apples.

Retaining the Chenath calculation engine is an absolute must, but we need to expand upon its ability to meet future design and construction requirements, such as improved airtightness, linear and geometric thermal bridging, window sizing and installation, heat pumps, heat recovery ventilation systems and any other low energy technologies that come to mind!

This additional detail, of course, is only of real value when we use appropriate climate files, which has been a point of discussion for over 10 years. So let's update those old files while we are at it and use predictive climate modelling to create a more resilient building stock!

Next steps

In a final point, in a post far wordier than intended, is the consultation timeline. Set out as a three-year process to engage industry, once activated in May 2022, will be subject to the typical lag of design and construction that is an inherent impediment to implementation.

Given the justified and overdue calls for a climate emergency, we should be working towards May 2022 as the date in which all new residential buildings must be completed under old permits or upgrade to NCC 2022 performance. If the provisions are finalised in November 2021, surely that is enough time to either finish your build or update to 2022. After all, you will likely get a better building as a result!


Recent Posts

See All