NatHERS Certificate Explained: What It Means for Your Build

A NatHERS certificate, short for Nationwide House Energy Rating Scheme, is mandatory for every new home in New South Wales. You cannot get construction approval without one. For homeowners planning a custom home in Wollongong or anywhere across the Illawarra, the NatHERS assessment shapes decisions about windows, insulation, orientation, and materials well before the first shovel hits the ground.

This post explains what a NatHERS certificate actually assesses, how it affects your build in practical terms, and why getting the assessment right early saves money later.

What a NatHERS Certificate Actually Assesses

A NatHERS assessment rates your home's energy efficiency from zero to ten stars. It models how well the dwelling will retain warmth in winter and stay cool in summer, using the design, orientation, windows, insulation, and construction materials as inputs. The minimum rating for a new home in New South Wales is seven stars, introduced under the national construction code update in 2023.

The assessment is not a physical inspection. It's a simulation run by an accredited assessor using software like AccuRate, FirstRate5, or BERS Pro. The assessor feeds in every relevant detail of your plans, including window sizes and glazing specifications, wall and roof construction, insulation values, floor type, and the home's orientation on your block. The software then models energy use across a full year based on the Illawarra climate zone and returns a star rating.

From 2025, NatHERS is expanding to also rate whole-home performance, including solar, appliances, and batteries. For now, the building shell rating is the one that drives approval.

How NatHERS Shapes Windows and Glazing in Your Build

Windows are the single biggest variable in a NatHERS assessment. Glass loses and gains heat faster than any other part of a home, so the ratio of glazing to solid wall and the performance of the window systems have outsized influence on the final rating.

Most custom homes in the Illawarra will need double glazing on at least some elevations to meet the seven star minimum. Coastal-facing windows in Woonona, Thirroul, or Kiama may need higher-performance systems. Homes with large glazing areas, particularly north-facing entertaining spaces, often require thermally broken aluminium frames or timber frames to pass the rating.

The cost implication is real. Double glazed and thermally broken windows sit well above standard aluminium systems. If your design features significant glazing, the NatHERS assessor will flag this early, and the window specification can become a meaningful line item in the overall cost of the build. Getting this assessed before plans are finalised is far cheaper than redesigning at tender stage.

How NatHERS Shapes Insulation in Your Build

The second biggest variable is insulation, specifically the R-values in your roof, walls, and floors. R-value measures how well a material resists heat transfer. The higher the R-value, the better the insulation performs.

A seven star rating generally requires insulation well above the old minimums. Roof insulation typically sits around R5 or higher, wall insulation around R2.5, and floor insulation becomes relevant for elevated floors, common on sloping blocks across Thirroul, Bulli, and the escarpment suburbs.

The NatHERS report will specify exactly what's required. Where it gets interesting is the trade-off between elements. A well-designed home with strong passive solar orientation, good eaves, and considered window placement might pass at seven stars with standard insulation. A home with poor orientation or lots of west-facing glazing might need significantly heavier insulation and higher-performance windows to get to the same rating. Neither is wrong. They're different paths to the same number.

What a NatHERS Certificate Costs and When to Get It

A NatHERS assessment for a typical custom home in the Illawarra is a few hundred to low thousand dollars depending on the complexity of the design. The report comes from an accredited assessor and forms part of your approval documentation, whether you're going through a complying development certificate with a private certifier or a development application through Wollongong City Council or Shellharbour Council.

The worst time to get the NatHERS assessment done is after the design is locked and tendered. If the assessment fails to hit seven stars, or returns at seven stars only with expensive specifications, you're either redesigning the home or absorbing significant cost you didn't plan for.

The right time is during design development. Bring the assessor in while the plans are evolving, so window placements, glazing specifications, insulation levels, and orientation can all be adjusted without redrawing the home. It's one of the cleanest examples of why engaging the right people early in a custom home build saves money later.

How TAG Homes Handles NatHERS for Custom Home Builds

TAG Homes builds across Wollongong, Woonona, Bulli, Corrimal, Figtree, Shellharbour, Kiama, and through to Vincentia on the South Coast. We work with accredited NatHERS assessors who understand the Illawarra climate zone and the specific cost and performance trade-offs for coastal, sloping, and escarpment sites.

We factor NatHERS into our pricing process early. When we provide a guide price on your plans, the energy rating implications are already considered. That means the fixed price contract you eventually sign includes the right window specifications, the right insulation, and the right construction detailing to hit seven stars without a nasty surprise at tender stage.

If you're planning a custom home in the Illawarra and want to understand how the NatHERS requirements will shape your build, give us a call. We can walk you through what the assessment typically looks like for your site type and what it means for the cost of the home.

0423 409 212 | www.taghomes.com.au

Frequently Asked Questions

Do I need a NatHERS certificate for a new home in Wollongong? Yes. A NatHERS certificate is mandatory for all new residential construction in New South Wales, including Wollongong, Shellharbour, Kiama, and the Illawarra. You cannot obtain construction approval without one, whether you're going through a complying development certificate or a development application.

What is the minimum NatHERS rating for a new home in New South Wales? Seven stars. The national construction code update in 2023 raised the minimum rating for new homes from six to seven stars. Higher ratings are possible and can be worth pursuing for long-term running costs, but seven is the current minimum to pass approval.

Does double glazing always mean a higher NatHERS rating? Not always, but usually. Double glazing reduces heat loss and heat gain through windows, which improves the energy model. However, orientation, glazing ratio, insulation, and construction materials all interact. In some designs, better orientation or heavier insulation can offset the need for double glazing across every window. Your assessor can model these trade-offs before you commit.

When should I get my NatHERS assessment done for an Illawarra custom home? During design development, before plans are locked in. A NatHERS assessor flagging an issue at design stage is a minor tweak. A failed assessment after tender is a redesign or a budget blowout. Engaging the assessor early is one of the simplest ways to avoid costly surprises in a custom home build.