NatHERS 7-Star Homes: Design Moves That Won’t Blow the Budget
Seven stars is the number that now shapes new home design across most of Australia. Under the National Construction Code (NCC) 2022 energy provisions, new houses must achieve a 7-star NatHERS thermal rating (alongside a separate Whole of Home energy budget), and in NSW the equivalent standard arrived through BASIX from October 2023. For builders, the question has moved on from “when does this apply?” to something more useful: what actually gets a design to 7 stars, and what does it cost?
The answer, from the thousands of simulations that energy assessors run, is consistent: 7 stars is overwhelmingly a design problem, not a products problem. Homes that reach it cheaply do so on the drawing board. Homes that reach it expensively do so at the glazing order. This article sets out the practical design moves — roughly in order of value for money — that the assessors at NathersPRO, part of the Rouse Hill–based Contrive group, use to get NSW projects across the line without blowing the budget.
First, understand what the star rating measures
A NatHERS star rating measures one thing: the predicted heating and cooling energy needed to keep the home comfortable in its climate zone, based on the building shell — floor plan, orientation, construction, insulation, glazing, shading and sealing. It does not count your appliances, your solar panels or your hot water system (those belong to the separate Whole of Home assessment under the NCC, and to the BASIX energy target in NSW). So you cannot buy your way to 7 stars with a bigger solar array; the shell itself has to perform.
Two consequences follow. First, every design decision that affects the shell affects the rating — which is why the cheapest path runs through early design. Second, the rating is climate-specific: the same house plan scores differently in Richmond, Orange and Coffs Harbour, because the software simulates it against local weather data. Never assume a design that rated 7 stars for one estate will rate 7 stars in the next one.
The high-value moves: free or nearly free
1. Orientation and room placement
The single most valuable move costs nothing: put the main living areas and their glazing on the north side, where winter sun is admitted and summer sun is easy to shade. Bedrooms, garages, laundries and bathrooms make excellent thermal buffers on the south and west. On a subdivision, this starts even earlier — lot orientation at the plan-of-subdivision stage determines how easily every future home on that lot will rate. When the Contrive group’s engineers and the urban designers at ARQI lay out a subdivision, solar orientation of lots is part of the brief precisely because it banks free performance for every builder who follows.
2. Right-size the glazing — especially west-facing
Windows are the weakest thermal element in almost every wall. Large areas of west-facing glass are the classic star-killer in NSW climates: they pour heat in on summer afternoons and leak it on winter nights. Before upgrading glass, reduce and rearrange it: trim oversized windows, swap a west-facing picture window for a highlight, move glazing area to the north. Reshaping the glazing schedule is often worth half a star before a single product is upgraded.
3. Shade the summer sun, admit the winter sun
Eaves are cheap and astonishingly effective. Correctly sized north-facing eaves block high summer sun and admit low winter sun — performance in both seasons from one piece of geometry. West and east glazing needs different treatment (vertical screening, deep verandahs, pergolas or external blinds) because the sun is low in the sky when it strikes those faces. A design with generous eaves and deliberate shading frequently outperforms a shadeless design carrying far more expensive glass.
4. Zone the plan
Doors between living zones and sleeping zones, hallways that can be closed off, and compact conditioned volumes all reduce simulated (and real) heating and cooling loads. Open-plan everything, double-height voids and stairwells open to living areas are all thermally expensive; where the market demands them, budget for the shell to compensate.
The mid-cost moves: specification upgrades that earn their keep
5. Insulation beyond the minimum
Ceiling insulation is the best-value bulk insulation in the house — upgrading it costs comparatively little and works every day of the year. Wall insulation upgrades, insulated or lighter-coloured roofing, and appropriate sarking membranes follow. Detail matters as much as R-value: compressed, gapped or missing batts around downlights and framing dramatically reduce real performance, so specify and inspect for coverage.
6. Improved glazing where it counts
Once the glazing schedule is rationalised, upgrade selectively. Double glazing (or high-performance low-E units) on the worst-performing orientations often achieves what whole-of-house upgrades achieve at a much lower cost. Frame material matters too — thermally improved or uPVC frames outperform standard aluminium. Your assessor can test options in the software and tell you exactly which windows are worth upgrading and which are fine as standard units; that report usually pays for itself several times over on the glazing order.
7. Sealing and ventilation
Draught sealing is cheap and chronically undervalued: weather-sealed external doors, sealed exhaust fans and dampers, sealed downlights, and attention to construction gaps. Ceiling fans in living rooms and bedrooms earn credit in the assessment and reduce real-world cooling demand. Together these small items can be worth a meaningful slice of a star.
8. Use thermal mass deliberately
A concrete slab exposed to north sun (polished, tiled — not carpeted) stores winter warmth and steadies summer temperatures. Waffle pod slabs, suspended floors and slab-edge exposure each interact differently with the rating depending on climate zone; this is one where modelling the specific construction, rather than guessing, prevents both under- and over-spending.
What usually doesn’t help
- Throwing products at a bad plan. A poorly oriented design with huge west glazing can swallow premium glazing and insulation and still miss 7 stars. Fix the geometry first.
- Copy-pasting a compliant design into a different climate zone or orientation without re-modelling. Star ratings do not travel.
- Over-specifying everything “to be safe”. Uniform gold-plating wastes money on elements that were never the problem. Simulation identifies the two or three items doing the damage; upgrade those.
- Confusing shell and appliances. Solar panels and heat pump hot water are valuable — for the Whole of Home and BASIX energy side — but they do not move the NatHERS star rating at all.
Process: when to involve the assessor
The pattern across projects is unambiguous. When a NatHERS assessment happens at concept stage — a preliminary run on the sketch plan, with feedback on orientation, glazing and shading — compliance costs are modest and documentation proceeds without surprises. When the first assessment happens after the DA drawings are locked, the remaining levers are the expensive ones. For volume builders, having each standard design pre-optimised, then re-checked per lot for orientation and climate zone, is the workflow that protects both margin and program.
Within the Contrive group, that early loop is built in: NathersPRO models designs while ARQI’s architects are still shaping them, so thermal performance is designed in rather than retrofitted — and the BASIX certificate at lodgement reflects a home the builder can deliver at the quoted specification.
Frequently asked questions
Is 7 stars mandatory for every new house?
Under NCC 2022, new houses in most of Australia must achieve a 7-star NatHERS rating plus a Whole of Home energy budget. In NSW, the equivalent standard applies through BASIX, which sets heating and cooling load caps aligned with 7-star performance for most new dwellings, with some concessions in particular climate zones and for some apartment buildings. Your certifier or assessor can confirm the exact requirement for your site and approval pathway.
What is the difference between the star rating and Whole of Home?
The star rating assesses the building shell — how much heating and cooling the home needs. Whole of Home is a separate score assessing the energy performance of fixed equipment: heating and cooling systems, hot water, lighting, pool and spa equipment, offset by solar. Under NCC 2022, new houses need both 7 stars and a Whole of Home score of at least 60; in NSW the equivalent equipment measures are addressed through the BASIX energy target.
Does 7 stars force me into double glazing?
Not automatically. Plenty of well-oriented, well-shaded designs reach 7 stars with improved but not premium glazing, particularly when window areas are disciplined. Poorly oriented designs with large glass areas usually do need significant glazing upgrades. The honest answer comes from modelling your actual design — which is exactly what a preliminary assessment is for.
Do dark roofs and render colours really matter?
Yes — solar absorptance of the roof (and to a lesser extent walls) is an input to the simulation, and in most NSW climates a lighter roof measurably reduces cooling loads. It is one of several low-cost levers, alongside sealing, fans and eaves, that add up to real rating movement without touching the budget’s big-ticket items.
Design to 7 stars with the Contrive group
NathersPRO (natherspro.com.au) delivers NatHERS ratings, BASIX certificates and concept-stage thermal advice across NSW as part of the Contrive group in Rouse Hill — with architecture, civil engineering, planning and telecommunications under the same roof. See our combined services or contact us to get your next design modelled early: +61 497 848 111, info@contriveconsultants.com.au.