A bloke in Balgownie sent me a set of plans he'd bought online, already mirrored. He'd flipped them so the garage landed on the side his crossover was on, which was a sensible instinct, and it took about four seconds standing on his block to see what else the mirror had done. The kitchen, the dining and the main living room were now facing west.
He'd have lived with it. West light is beautiful at six in the evening in September. It is not beautiful at four in the afternoon in January, and more to the point the thermal performance assessment came back short, so either the design changed or the glass did. Upgrading that much west-facing glazing would have cost him more than redrawing the plan the right way round, and the redraw gave him a better house into the bargain. We redrew it.
That's really the whole argument for understanding this stuff before you fall in love with a plan rather than after. The energy side of a new build is usually treated as a box that gets ticked somewhere between the drawings and the lodgement, by someone you never meet, and it isn't. It's a set of design decisions, most of which are free if you make them early and expensive if you make them late.
What BASIX is, and where it sits
BASIX is a certificate, and every new dwelling in NSW needs one. Renovations over a cost threshold and pools over a certain size need one too. The standards cover three things: how much water the house uses, how much energy it uses, and how the building itself performs thermally. The NSW Planning Portal runs the tool and publishes the detail, including the fact that the standards were increased on 1 October 2023 — which is why anything you read from before then feels a bit soft compared to what your assessor is telling you now.
It is not your approval. It's a document that travels with your approval, and it applies on either pathway. I've set out the complying development versus DA fork properly in CDC versus DA in NSW; BASIX sits alongside both.
The part people miss is what happens after the certificate is issued. Everything on it becomes a commitment, and the commitments get checked. More on that below, because it's the bit that costs money when it goes wrong.
The rating is a model of your house on your block
Thermal performance is assessed by modelling, not by a checklist. An accredited assessor takes the actual plan, the actual orientation, the window sizes and glass types, the insulation, the wall and roof construction, and runs it through software that estimates the heating and cooling the house will need across a year. What comes out is a star rating on the scale run under the Nationwide House Energy Rating Scheme, which the Commonwealth publishes at homeenergyrating.gov.au.
The word doing the work there is your. Two identical houses rate differently on two blocks if they face different ways. Same drawings, same builder, different number. Which is why "this design has been built forty times and it's fine" is not an answer, and why the plan that suited a family in Albion Park with the fall running north can come back short on a block in Corrimal that faces the other way.
It also means the rating responds to things you can actually change on paper. Move a window, change its size, add an eave, swap the glass, lift the insulation. Each of those is a lever, and they cost wildly different amounts.
Orientation is the free one
If you take one thing from this: the cheapest energy performance you will ever buy is the decision about which way the house faces, and you buy it at sketch stage for nothing.
Living areas to the north, where they get sun through the middle of a winter day and where a properly sized eave shades them in summer, because the summer sun is high and the winter sun is low. Bedrooms east if you can, so they're warm in the morning and cool by bedtime. Bathrooms, laundry, hallways, the garage and the pantry pushed to the south and west, where they can absorb the bad aspects on your behalf. Small windows on the west, or none.
Every one of those is free while the plan is a sketch. None of them is free once the slab is set out. And on a block where the good outlook fights the good aspect — very common down here, where the view is often east to the water and the sun is north — the compromise is a design conversation worth having properly. There are ways to get both, usually involving where you put the outdoor living space and how you shade the east glass, and they're much easier to solve on a screen. Blocks with a fall give you more options again, which I've gone through in building on a sloping block.
Where the improvements are cheap, and where they aren't
Once the plan is oriented sensibly, the rest is fabric. Insulation in the ceiling, the walls and, depending on the floor construction, under the slab or floor. Glass, which is the weakest part of any wall and the single biggest lever after orientation. Sealing, which nobody thinks about and which quietly decides whether your heating stays inside.
Rough order of value for money, in my experience on Illawarra jobs: ceiling insulation is cheap and does a lot. Eaves and external shading are cheap and do a lot, and they also stop the house looking like a shoebox. Better glass on the west and east is expensive per square metre but sometimes the only fix, which is exactly why you'd rather not need much of it. Wall insulation above the standard is moderate. Underfloor insulation on a suspended floor is worth it and often forgotten.
What doesn't work is trying to buy your way out of a badly oriented plan at the end. You can spend a fortune on glazing to rescue a west-facing living room and end up with a house that rates adequately and still cooks at four in the afternoon. The rating is a model; the summer is not.
Worth knowing too that the base specification from most builders meets the minimum and stops there, which is a perfectly reasonable place for a base spec to sit. Insulation and glazing above that minimum show up on the inclusions list as upgrades, and I've written about how that document behaves in reading a new home inclusions list.
The certificate becomes a set of conditions
Here's the mechanic that catches people late in a job.
Once BASIX is issued, the commitments on it are not suggestions. The certifier checks them, and the occupation certificate depends on them. If the certificate says a particular glass type in the western windows, that glass goes in. If it says a rainwater tank of a given size plumbed to particular fixtures, that tank goes in and gets plumbed that way. If it says a certain insulation value in the roof, that's what the insulation contractor installs, and the certifier will look.
Which means the moment somebody suggests trimming the tank or downgrading the glass to claw back budget in month five, the honest answer is that you can't, not without going back and having the certificate redone to show the house still complies some other way. Sometimes that's possible and it costs a fee and a delay. Sometimes it isn't.
I'd rather clients knew that going in. Value engineering a build is normal and often sensible, but the BASIX commitments are the wrong place to look for savings, and a builder who quietly substitutes something cheaper is handing you a problem at occupation certificate stage rather than saving you money.
All-electric, and whether you bother with gas
More of the new houses we build now have no gas connection at all, and it's worth thinking about deliberately rather than by default.
An all-electric house means induction cooking, a heat pump hot water system, and reverse cycle for heating and cooling, usually with solar on the roof. What you avoid is the connection cost and the daily supply charge for a service you're barely using, which on a house with one gas appliance left is money for nothing.
The honest caveats. Induction genuinely cooks well and a lot of people who were sceptical are converts, but if you have cast iron you love and pans that aren't magnetic, you're replacing them. A heat pump hot water unit makes some noise and lives outside, so it needs a sensible spot that isn't under a bedroom window or hard against the neighbour's. And the switchboard and supply have to carry the load, which is a conversation with your electrician at design stage rather than a surprise later.
Solar is the other half of it. A north-facing roof plane sized for a decent array is a thing to design in, not to retrofit around a hip you've already built, and if there's any chance of a battery later, the space and the cabling are cheap to allow for now.
I won't claim all-electric is the right answer for every household — it depends on what you cook on and what you're replacing. I'll say that on the last dozen or so new homes we've priced, the gas connection has been hard to justify.
Get the assessment early, not at lodgement
The way this usually runs is that a design gets drawn, documented, priced, and then sent for a BASIX assessment as part of preparing the lodgement. By then the window schedule is set, the elevations are resolved, and any change the assessor asks for is a change to finished documentation.
The better version is a preliminary assessment on the concept plan, when it's still a sketch and moving a window costs a phone call. You find out early whether the design gets there on fabric alone or whether it needs help, you learn which windows are carrying the problem, and you make those decisions while they're free. On our jobs the assessor sees the concept before the client sees a price, because a fixed price built on a design that hasn't been tested isn't much of a fixed price.
Money-wise, none of this is the big lever on a build — the ranges and what actually drives them are in what it costs to build a house in NSW. But it's one of the few areas where the good decision and the cheap decision are the same decision, provided you make it early enough.
We build custom new homes across Wollongong, the Illawarra and the Southern Highlands, and the orientation conversation happens on your block with the plan on the bonnet before anything gets drawn properly — that's how we run new homes. If you've got a plan you like and you're not sure how it sits on your land, send it through the contact page or ring 0434 037 851. Tell me which way the street runs and I can usually tell you the answer standing there.
Want a hand with this at your place? Get a free quote or call 0434 037 851.