NatHERS Energy Rating: What the 6-Star Minimum Means for Your New Home in Tasmania

Every new home in Tasmania must achieve a minimum 6-star NatHERS energy efficiency rating before a building permit is issued. The rating tells you how hard your heating and cooling system will have to work — and a home that just scrapes 6 stars will cost considerably more to run than one designed for 7 or 8. This guide explains what NatHERS is, how the rating is calculated, and the design decisions that move the needle most in Tasmania's Climate Zone 7.

What Is NatHERS?

NatHERS (Nationwide House Energy Rating Scheme) is the Australian Government framework for rating the thermal performance of residential buildings. It uses accredited software to simulate how a building responds to a full year of local weather data, and expresses the result as a star rating from 0 to 10. A higher rating means the building envelope — walls, roof, floor, and windows — does more of the work of keeping you comfortable, and the mechanical heating and cooling system does less.

The simulation covers the building fabric only — insulation levels, window performance, orientation, mass, and shading. It does not include the efficiency of your heating system, hot water, appliances, or solar panels. This is an important distinction: a 6-star rated home with a low-efficiency gas heater may cost more to run than a 7-star home with a high-efficiency reverse-cycle heat pump.

NatHERS assessments are carried out by accredited assessors using software tools approved under the scheme (AccuRate Sustainability and FirstRate5 are the most common in Tasmania). The assessor works from the building plans and specification — so the assessment happens during the design and documentation stage, before construction begins.

The 6-Star Minimum: When Did It Apply in Tasmania?

The 6-star NatHERS minimum for new homes (Class 1 residential buildings) was introduced under the National Construction Code 2022 (NCC 2022) and came into effect in Tasmania on 1 May 2023. Homes that received a building permit before that date could be assessed under the previous 5-star minimum, but any permit issued since 1 May 2023 requires a minimum of 6 stars.

The 6-star minimum applies to the whole home as a single assessment, not room by room. Extensions and alterations have different requirements depending on their scope — your building surveyor and council can advise on what applies to your project.

Tasmania Is Climate Zone 7 — What That Means for Design

Under NatHERS, Australia is divided into 70+ climate zones. Northern Tasmania (including the Sheffield/Devonport/Launceston corridor where Davies builds) sits within Climate Zone 7 — cool temperate. This zone is characterised by cold winters with significant heating loads, mild to warm summers, and moderate rainfall throughout the year. Westerly winds off Bass Strait add wind-driven rain and heat loss factors that don't apply to mainland locations at similar latitudes.

Because heating is the dominant energy load in Climate Zone 7, the design factors that matter most are those that reduce winter heat loss:

• Ceiling insulation — the single highest-impact item (heat rises; the ceiling plane loses the most energy)
• Wall insulation and external cladding type — bulk and reflective insulation together outperform either alone
• Window thermal performance — U-value (heat loss rate) and solar heat gain coefficient (SHGC) matter more here than in warmer climates
• North-facing glazing to capture passive solar gain during winter
• Air sealing — uncontrolled infiltration through gaps is a significant heat loss pathway in windy Tasmania
• Slab edge insulation — concrete slabs conduct heat to the ground without it

Summer overheating is a secondary concern in northern Tasmania, but it is growing in significance. Eaves, verandas, and external shading devices that block high summer sun while admitting low winter sun are the most effective passive cooling strategy — and they are far cheaper to include at design stage than to add retrospectively.

What Affects the NatHERS Rating Most?

6 Stars Is the Minimum — Not the Target

A home that just meets the 6-star minimum is compliant — but compliance and comfort are not the same thing. The difference in running costs between a 6-star and an 8-star home is significant over the life of the building. Energy modelling studies suggest that each star of improvement reduces heating and cooling energy consumption by roughly 15–20%, though the actual saving depends heavily on the household's energy sources, appliance choices, and thermostat habits.

Davies Design & Construction has been building in northern Tasmania since 2009. Our design approach targets a rating well above the 6-star minimum as a matter of course — not because it is required, but because a thermally comfortable home that costs less to run is a better home. The insulation specifications, window performance, and passive solar orientation we use on a standard custom home typically put the NatHERS result in the 7–8 star range without meaningful cost premium over a code-minimum build.

Passivhaus-certified homes achieve 8–9+ stars on NatHERS, driven by very high insulation levels (R8+ ceiling, R6+ walls), triple glazing with thermally broken frames, and controlled mechanical ventilation with heat recovery. For more on the Passivhaus standard and what it means for Tasmanian homes, see our Passive House in Tasmania page.

How the NatHERS Assessment Fits Into the Building Process

A NatHERS assessment is completed during the documentation phase — once the building plans and specification are finalised but before the building permit is lodged with council. The assessor needs:

1. Site orientation — which way is north relative to the building
2. Floor plan and elevations showing window and door positions and sizes
3. Construction specification — wall, ceiling, and floor build-up and insulation R-values
4. Window schedule — frame type, glazing type, and U-value/SHGC for each window and door
5. Roof type and colour

The NatHERS certificate is one of several documents submitted as part of the building permit application to your local council. The building surveyor assesses the design against the NCC including the energy efficiency requirements before issuing a Certificate of Likely Compliance. For more on the permit process, see our guide to building permits in Tasmania.

Importantly, changes to the building design after the NatHERS assessment is complete may require a revised assessment — particularly if window sizes, positions, or glazing specifications change. Settling the design before the assessment saves time and avoids revision fees.

Common Questions About NatHERS in Tasmania

Does NatHERS include solar panels or the heating system?

No. NatHERS assesses the thermal performance of the building envelope only — walls, roof, floor, and windows. Solar panels, the heating/cooling system, hot water, and appliances are assessed separately under other sections of the NCC (specifically the Section J whole-of-home energy budget pathway). A high NatHERS star rating combined with an efficient heating system and solar panels is the most cost-effective combination.

Can I improve a low NatHERS rating after construction?

Yes, but it is more expensive than getting it right at design stage. Adding ceiling insulation to an existing home is straightforward and worthwhile. Improving wall insulation or replacing windows on a completed building is costly and disruptive. The most effective intervention for existing homes with single-glazed or older double-glazed windows is window replacement — this is the biggest single upgrade available after construction. See our guide to windows and glazing for Tasmanian homes for what to look for when specifying windows at design stage.

What NatHERS rating do I need for a home loan?

Lenders do not currently require a specific NatHERS rating for standard home loans. However, some lenders offer green home loans with preferential rates for homes that achieve 7 stars or higher, or that meet specific energy efficiency criteria. This is an evolving area — if this is relevant to your project, check with your lender or broker about current offerings.

Is there a difference between NatHERS and BASIX?

Yes. BASIX (Building Sustainability Index) is a New South Wales-specific scheme and does not apply in Tasmania. NatHERS is the national scheme and is the relevant energy efficiency assessment framework for all Tasmanian new homes. If you have experience building in New South Wales and are now building in Tasmania, the NatHERS star rating pathway replaces the BASIX certificate requirement.

How Davies Approaches Energy Efficiency Design

Since 2009, Davies Design & Construction has built custom homes across northern and north-west Tasmania. Energy efficiency has been central to our design philosophy throughout that period, and our approach has refined as materials, software, and the NCC have evolved.

We coordinate with our architectural partner Align Architecture & Interiors at the concept design stage to lock in orientation, eave depth, and window placement before the floor plan is finalised — because these decisions are cheapest when made on paper. Insulation specifications, glazing performance, and air sealing details are resolved at the documentation stage and carried through to site.

The result is a home that performs well without relying on expensive mechanical backup — and that is comfortable to live in across all seasons. See our guide to insulating a new home in Tasmania and our passive solar design guide for more on how we approach building performance.

Ready to Discuss Your New Home's Energy Performance?

If you're planning a new home in northern or north-west Tasmania and want to understand what a 7-star-plus NatHERS design looks like in practice, we'd be glad to walk you through it. Get in touch to start the conversation — or explore our Building in Tasmania guide for a broader overview of the new home building process.