NCC 2022 and NatHERS Star Ratings – eTool Position Statement

NCC 2022 are proposing some dramatic improvements in residential energy use. This is, in principal a fantastic development and one that eTool very much supports. We do however feel that mandating 7 star NatHERS performance carries some risk and isn’t the most effective deployment of available capital for rapid decarbonisation. The reason is simple, there is much lower hanging fruit available in areas not covered by the NCC proposed changes.  It’s also highly likely that the 7 Star requirements will lead to net-negative outcomes for the planet.

See below examples of the life cycle impacts (Global Warming Potential) of three detached residential buildings designs in each capitol city (averaged) selected because of their ubiquity (the homes selected are very standard display home products), plus an overall national population weighted average. Due to their relatively large size (and hence large thermal loads in comparison to other impacts) they represent a somewhat “best case” scenario of what improving thermal performance can achieve. The charts below indicate that moving from 6 to 7 stars doesn’t significantly move the needle on life cycle global warming impacts.  Although moving from 6 to 7 stars delivers a 25% (average) saving in heating and cooling energy requirements, it only results in an average 2% reduction in life cycle impacts.

Life Cycle Impacts of 7 Star NatHERS NCC 2022

While this change could make sense for particularly hot or particularly cold climates, such as Darwin, Hobart and Canberra, it makes significantly less sense for the more temperate areas of Sydney, Melbourne, Brisbane, Adelaide and Perth.  So, the question is, can Australian new home buyers get better bang for buck elsewhere?  The “Other Impacts” are broad (see below for a breakdown for the population weighted average example), but the two largest categories are outside of the proposed scope for NCC 2022.  So, while eTool are supportive of improved thermal performance of buildings, we also see inherent risk associated with targeting this strategy in isolation.  That is because, for homes to “rate” 7 stars in many temperature climates they require a lot of thermal mass (e.g. brick and concrete), so what the 2022 NCC may end up doing is discouraging the use of low carbon materials such as timber in preference of brick and concrete for thermal mass.  This will in turn result in higher life cycle material impacts and ultimately higher net impacts, working against the intended goals of the amendments (to reduce greenhouse gas emissions).

Likewise, plug loads are another area – currently outside the NCC – that requires attention.  Solar PV most certainly should play a role in reducing the impacts of the building, energy monitoring, and possibly other policy levers the government can pull to improve the energy efficiency of appliances.  There’s other easy wins that should be addressed, higher efficiency HVAC, lower GWP refrigerant gases are good examples.  Ultimately, life cycle assessment should be the cornerstone of any policy for reducing the environmental impacts of Australian residential and commercial buildings.

Life Cycle Impacts Australian Residence