More Energy Efficiency Regulation Changes

Lately the building industry has been in a constant state of change. With building regulations changing and then clarifications and amendments, these changes make it hard to keep a handle on where we stand.

Energy Efficiency assessments are no different.

The change to 6 star regulations in Western Australia last May was a huge change for the building and design industry. This has been followed this May with further changes. These changes are due to clarifications from the government body that regulates residential Energy Efficiency assessments, NatHERS.

The BCA states that a residential energy efficiency assessment that is conducted using the NatHERS protocols and achieves 6 stars have satisfied the energy efficiency regulations. It is therefore important that you are not only getting a residential energy assessment but one that complies with the NatHERS protocols, so that you are not left with a non compliant building.

The NatHERS regulations set out what software can be used and how the assessment must be conducted. It is these NatHERS regulations that have changed as of May 1st. This has resulted in a more stringent assessing procedure and has had a negative effect on most ratings.


So what are the changes and how does it affect you?

The changes can be broken into 4 key areas:

Zoning Changes

When an assessment is conducted a house is broken into zones. Each zone is given a different usage pattern ( E.G. a bedroom is night time use) and noted if the area is heated or cooled.

There was previously freedom to choose the usage and if the area was heating and cooled. This is no longer the case. All areas, except wet areas are considered heated and cooled and all areas except bedrooms are considered day time use. The only exception to this is a study – which can be determined as night time use if it has a robe and could be used as a bedroom.

This can have a significant impact on the energy rating, as daytime uses generally result in higher energy uses and therefore a lower rating.


Previously medium was the default colours of walls and roof if none were noted. Although this still remains for walls, the assessment must now be conducted using worst case roof colour. In the metropolitan and southern areas Light is generally the worst colour. In the northern areas it is dark.



Adjoining structures can have a large impact on the energy efficiency of a house. If a house is shaded on the north side by a neighbouring house, or has the cooling sea breezes blocked this will reduce the energy rating it achieves. Previously it was only required to enter obstructions that were shown on the site plan. This is no longer the case.

We now assume that there will be an identical house built next door if it is vacant, or the house is not shown on the site plan.



Recessed down lights, whatever type they are, have a negative impact on our ratings, for 2 reasons.

Firstly a clearance must be left between down lights and ceiling insulation. This results in a hole in the ceiling insulation that allows heat and cold to escape, affecting the overall ceiling insulation properties.

Secondly if Down lights are vented this allows a passage for uncontrolled air movement


Although the Building Commission has advised that only directional or gimbled lights are considered vented, if it is not noted on the plan we now need to assume all Down lights are vented. If no electrical plan is provided we are to assume that there will be 4 down lights per 10m². This will result in a significantly reduced rating and extra costs in compliance.


What to do?

You will have found that the ratings you have received from May 1st have been lower and possibly requiring greater upgrades. If not, check with your energy assessor that the latest rules are being applied.

Ensure your Energy efficient home plans have the following information to assist with an accurate rating:

Roof Colour (If Known)

Neighbouring structures shown on your site plan

Note on electrical plan if Down lights are to be unvented

If no electrical plan is provided note if there will be recessed down lights on the floor plan.


And of course if you have any questions talk to us here at Sustainability WA. If you don’t have an energy efficiency assessor on your team already perhaps it is time to consider engaging Sustainability WA to work with you as part of your design team.


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