The Study

Over the last few weeks we have looked at the impact of NCC22 on energy compliance due to the updated weather files, adjusted star bands and different rules for how assessors must model.

We looked at ten houses across nine climate zones and two NCC versions - a total of 180 simulations!

The big winner appears to be Climate zone 54 - Mandurah, with all ten houses getting a boost in performance under NCC22. Zone 49 - Katanning appears to be the hardest hit by the changes, with not only a jump from six to seven stars, but the adjusted ratings mean an extra 0.30 stars or so will need to be found!

Of the 180 simulations - the largest jump was +0.8 stars in Zone 33 - Broome, and the largest drop was -0.7 stars in Zone 49 - Katanning. 80% of results were within 0.4 stars between versions. The average across all zones and all dwellings was +0.09 stars from NCC19 to NCC22

There were not any really clear patterns for the dwellings themselves - some dwellings enjoyed a boost in one zone along with other dwellings, but in another zone has taken a drop where other dwellings have gone up. It might be that dwellings with higher heating and/or cooling loads perform differently in the zones.

Please note the maps I have included are indicative only - climate zones work on postcodes. You can search the appropriate zone by using the NatHERS climate zone map
https://www.nathers.gov.au/themes/custom/govcms8_uikit_starter/climate-map/index.html

We hope this little study into the changes between NatHERS versions has been interesting - would you like to see further info like this?

Nationwide House Energy Rating Scheme (NatHERS) | Climate Zone Map Disclaimer: The Climate Zone Map is provided for general reference only and was last updated in March 2013. It should not be relied on for accurate climate zone information. You should exercise your own skill and care when using the Climate Zone Map and carefully evaluate the accuracy, currency, com...

The last climate zone we have looked at in this project is Zone 49 - Katanning. This zone covers the inland areas of the SW of WA - and includes the townships of Kojonup, Cranbrook, Wagin and Boyup Brook .

Only 160 dwellings have been certified in the last three years, and all between 6.0 and 7.4 stars - according to the Aust. housing data portal.

Our ten test houses rated at 6.37 stars on average in this climate zone under NCC19. Updated for NCC22 - the average rating dropped to 6.05 stars, a reduction of -0.32 stars.

While two dwellings did enjoy a small improvement of +0.2 stars, generally the designs had a reduction in performance, up to -0.7 stars for two designs.

What does this mean?
The updated weather files and star bands for Zone 49 are not likely to be favourable in this climate zone, and could be considered that stringency is being increased significantly in this zone. Ideally - a rating of at least 7.3 stars should be targeted under NCC19 to retain compliance under NCC22.