The National Construction Code (NCC) aims to provide a uniform set of guidelines to ensure equivalent minimum standards of construction are achieved across the country. But how will the guidelines treat the variations in performance in homes that are in close proximity to State or Territory borders, or in different climate zones? CSR’s Scott Clarkson gives an example of two couples in the ACT and NSW, who live 15 minutes away from each other, but whose homes display significant variations in energy efficiency performance. By Scott Clarkson*John and Kate have been living in their new home in Googong, NSW, for about 18 months. Their good friends, Sam and Jane also moved into their new home in Gilmore, ACT, around the same time. Both couples used the same builder. Both couples also have similar tastes, the same number of children and live in a similar style – so they chose the same home design as each other.
Coincidentally they both built in new developments, both houses face east, and their homes are just 15 minutes away from each other.
Googong’s John and Kate make the short drive to a dinner party at Sam and Jane’s during a cold snap in August. Snow has dusted both properties and the kids have been making snowmen at both houses. John and Kate arrive for dinner and can’t believe how warm Sam and Jane’s home feels.
Over dinner Googong John comments that Sam and Jane must spend a small fortune on heating. After discussing energy companies and electricity charges, John and Kate wonder how they’re paying almost $500 per year more in heating and cooling energy bills while their own home feels colder than Sam and Jane’s.
While this cosy ACT/NSW example may seem a little far-fetched to some, the facts tell us homes built in the same vicinity as each other can have significant variations in performance due to their proximity to State or Territory borders or even simply being in different climate zones.
Cross border confusion
Builders and trades working across State and Territory boundaries can also be forgiven for being a little confused by State and climate-based variances. When it comes to energy efficiency provisions, the National standard of 6 Star thermal rating is required for class 1 buildings (detached houses).
However dig a little deeper into the current BCA Volume 2, or any of its predecessors and the State-specific building codes, and you’ll find some great variances in the minimum performance allowed.
In Victoria, for example, 6 Star performance is accepted as holding true to the stated aim. The ACT, South Australia and Tasmania also have a true 6 Star performance requirement. When we cross some other borders however the picture gets somewhat confused.
If you’re in Climate Zones 1 or 2 (relevant for parts of WA, NT & QLD), an outdoor living space (>12 metres squared) with ceiling insulation and a ceiling fan permits a concession of 0.5 star each, so 5 Star performance is theoretically required. The remainder of WA is required to achieve 6 Star rating.
The Northern Territory however, simply ignores any improvements introduced over the last 10 years. At CSR, we dragged out the BCA 2005 from our archives (lucky our library still has this) and flicking through the dust covered pages we end up at a performance aim of 3.5 Stars for the NT!
In Queensland a further 0.5 Star concession is given if you install a solar PV system, with a total of 4.5 Star if you’ve already put fans and insulation into your alfresco area.
NSW provisions refer us to BASIX which averages out at 4.5 Star (note this overrides the Climate Zone 2 parts of Northern NSW). NSW Planning states that the other provisions of BASIX (water and lighting/appliance energy) more than account for the reduced targets for thermal performance.
Performance dividing line
For the purposes of our sample homes in the ACT and NSW, we engaged our team of energy raters and building science experts to analyse two theoretical houses with identical air conditioners and occupancy profiles – where lighting, hot water and appliance selection were assumed to be identical. The ACT location was required to achieve a 6 Star NatHERS rating and would require approximately 3800 kW.hr of electricity per year running a 3.5 Star reverse cycle A/C unit. The house in Googong, however, would need a touch under 5450 kW.hr of electricity per year. At a typical total electricity cost of $0.30 per kW.hr (including infrastructure and supply charges) the ACT house saves almost $490 per year.
The material specifications for each location are included in the following table:
|BASIX vs BCA||Googong, NSW 2620||Gilmore, ACT 2905|
|NatHERS Star Rating||4.5 Star||6.0 Star|
|Window Performance||U 6.34 & SHGC 0.72||U 4.33 & SHGC 0.56|
|Sliding Door Performance||U 6.2 & SHGC 0.69||U 4.1 & SHGC 0.61|
|Window & Sliding Door Construction||Single glazed AL frame||Double glazed AL frame|
How to raise the standard
Similar analysis has been conducted that demonstrate such scenarios are repeated around the country with similar results. While it is common knowledge that BASIX in NSW falls below the National Standard, it is not as widely known that other inter-state geographic boundaries and intra-state climate boundaries also create inequality for residents simply living on the wrong side of the road, in some cases.
In NSW, QLD, NT and other regions where minimum compliance levels are somewhat below the National Standard, consumers can save themselves thousands of dollars over the life of their home by simply asking their builders to increase the insulation and glazing levels to above what the local building code requires. Builders who exceed building code performance will pleasantly find that their clients are happier with the finished house and through word of mouth their reputation and referral rate is likely to improve.
As for other States, don’t rest on your laurels – 6 Star is still only 6 out of 10! Look for an extra R0.5 or R1.0 in your insulation and look for the next best level of glazing, whether it is Low E or double glazing (it works in all climates).
If only John and Kate knew that all they had to do was ask for an ACT compliant home before they built.
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