Climate Zone: When is it reasonable to use a secondary climate zone?

Region: All States

Assessor Question:

At what point is it reasonable to use secondary climate zones please?

I have a project in Echuca. Echuca climate zone is Ballarat, with a secondary of Mildura. Moama on the other side of the river is also Mildura zoned.

With all things equal; With climate zone Ballarat the rating is 5.3 stars, with cooling load only 4% of the total energy loads.

with climate zone Mildura, the rating is 6.3 stars, but the cooling load is 33% of the total load, which might be a bit more realistic although also maybe overstated due to latitudinal differences.

I can get the rating to 6 stars in the Ballarat zone, that’s not an issue. But the inclusions to do so are more focused on a cold climate which may overheat the house in reality if the climate is generally warmer than zoned.

Generally I wouldn’t consider the secondary climate zone, however for Echuca the Ballarat climate zone just doesn’t sit well for me, and the two climates zones are wildly differing. 

TechLink Response:

• NatHERS Climate Zones have boundaries defined by postcodes.
• These do not necessarily always align well with actual climate profiles.
• They often coincide with rivers, as this case with the Murray River.
• Echuca has a default Climate Zone of 66 - Ballarat whereas Moama on the opposite bank of the river is Climate Zone 27- Mildura.
• A similar discrepancy occurs with Albury and Wodonga.
• Climate Zone 66 - Ballarat is for an altitude that is much higher than Echuca and experiences very cold winter conditions.
• Local knowledge and local BOM weather station data can be used to substantiate the selection of more appropriate climate zones.
• Climate zone 27 - Mildura or 20 - Wagga will be better for Echuca than 66 - Ballarat.  
• A note on the additional information page of the NatHERS Report should be provided to substantiate the decision for selecting an alternative Climate Zone.