NatHERS 7 Star Rating and Whole-of-Home Explained: NCC 2025 Energy Requirements for New Houses (2025 Guide)
A new house on the NCC 2025 energy rating pathway needs a NatHERS rating of 7 stars, inside separate heating and cooling load limits, and a whole-of-home rating of 60 (Specification 42). In climate zones 1 and 2 a qualifying outdoor living area lowers the star rating to 6.5, or to 6 with a ceiling fan. This guide sets out both pathways in Part H6, the elemental route in Housing Provisions Section 13, the state and territory variations, and a checker for your ratings.
A new house on the energy rating pathway has two numbers to reach: 7 stars on its NatHERS certificate, and a whole-of-home rating of 60. Both come from Specification 42 of the National Construction Code (NCC) 2025 Volume Two. Behind them sit two Performance Requirements, separate heating and cooling load limits, a list of construction details that a good rating does not excuse, and an elemental alternative in the ABCB Housing Provisions.
This guide sets out each rule with its clause, in the Code's own order, including the outdoor living area concession in the north and the state variations. The checker in section 9 tells you which star rating your house needs and whether its two numbers pass.
In one minute
Two Performance Requirements, two ways to meet each. H6P1 limits the heating and cooling loads. H6P2 limits the energy value of the domestic services. H6D2 meets each by Option 1, house energy rating software under Specification 42, or Option 2, the elemental provisions of Housing Provisions Section 13.
7 stars, inside three load limits. S42C2(1) asks for an energy rating of at least 7 stars, including the separate heating and cooling load limits. Those limits are in the ABCB Standard for NatHERS Heating and Cooling Load Limits (S42C2(2)).
6.5 or 6 stars in climate zones 1 and 2 with a qualifying outdoor living area under a roof of Total R-Value 1.5 or more. It must open directly off a living area and have at least 12.0 m², 2.5 m each way, a 2.1 m opening height, and one permanently open side plus a second open or openable, 900 mm clear of a boundary or obstruction. The 6-star band also needs a ceiling fan (S42C2(1)(b), (c), (3) to (5)).
A whole-of-home rating of at least 60 (S42C3), with the services in Part 13.7, satisfies H6P2. Neither rating excuses insulation installation, thermal breaks, slab edge insulation or building sealing (S42C4).
The elemental route has its own energy calculation in Housing Provisions 13.6, open only to a house of up to 500 m² total floor area (H6D2(2)(b)). NSW, the Northern Territory and Tasmania vary Part H6.
1. Where the energy rules for a house sit
The energy efficiency rules for a house are in Part H6 of NCC 2025 Volume Two. Its objective is to reduce energy consumption and energy peak demand, reduce greenhouse gas emissions, and improve occupant health and amenity (H6O1).
Specification 42, at the back of Volume Two, holds the energy rating pathway. Section 13 of the ABCB Housing Provisions holds the elemental provisions and the construction details both pathways share.
Section 13 applies to a Class 1 building and to a Class 10a building with a conditioned space (13.2.1, 13.4.1, 13.6.1). A conditioned space is one heated or cooled by the building's domestic services (Schedule 1). Part 13.7, services, also reaches any Class 10a building and a Class 10b swimming pool associated with the house (13.7.1). Our building classes guide explains Class 1 and Class 10. Class 3 and Class 5 to 9 buildings are covered by Volume One Section J, set out in our Section J guide.
Two Performance Requirements carry the Part. H6P1, thermal performance, says the total heating load, cooling load and thermal energy load of the habitable rooms and conditioned spaces must not exceed limits calculated in Specification 44. Specification 44 calculates them from climate data for the building's location and the total area of its habitable rooms (S44C2 to S44C4).
H6P2, energy usage, says the energy value of the building's domestic services must not exceed 70% of the energy value with a reference set of services (H6P2(1)). The reference set is a 3-star ducted heat pump heating all heated spaces and cooling all cooled spaces, a 5-star instantaneous gas water heater for all hot water, and 4 W/m² of lighting.
The NCC defines energy value as the net cost to society, including costs to the building user, the environment and energy networks. It defines domestic services as heating, air-conditioning, mechanical ventilation and artificial lighting; pumps and heaters for swimming pools and spa pools; heated water systems; and on-site renewable energy equipment. Cooking facilities and portable appliances are excluded (Schedule 1).
A Performance Solution can be verified against H6P1 with H6V2, which compares the house with a reference building using a calculation method other than house energy rating software, and H6V3, which verifies the building envelope sealing by an air permeability of not more than 10 m³/hr.m² at 50 Pa (AS/NZS ISO 9972 Method 1). Both apply only to a Class 1 building and an enclosed Class 10a building attached to it (H6V1).
2. Two ways to comply
The Deemed-to-Satisfy route is H6D2, and it sets out the choice twice, once for each Performance Requirement.
H6P1, thermal performance, is met by S42C2 using house energy rating software, together with S42C4(1). Or it is met by Housing Provisions Part 13.2 (building fabric), Part 13.3 (external glazing), Part 13.4 (building sealing) and Part 13.5 (ceiling fans) (H6D2(1)).
H6P2, energy usage, is met by S42C3 using house energy rating software, together with S42C4(2). Or it is met by Parts 13.6 and 13.7, for a building with a total floor area not greater than 500 m² (H6D2(2)).
The explanatory note to H6D2 calls these Option 1, energy rating, and Option 2, elemental provisions.
House energy rating software, for Specification 42, means software accredited under the Nationwide House Energy Rating Scheme (NatHERS) (Schedule 1). Where the software is required, its output must be evidenced by a NatHERS certificate issued in accordance with the NatHERS scheme (Volume Two A5G9).
3. Option 1: the 7-star rating
S42C2(1) is one sentence with three branches. A building must achieve an energy rating, including the separate heating and cooling load limits, using house energy rating software, of greater than or equal to 7 stars. In climate zones 1 and 2 the threshold drops to 6.5 or 6 stars where the house has a qualifying outdoor living area (section 4).
The words "including the separate heating and cooling load limits" do real work. The explanatory note spells it out. The modelled energy loads of a building must not exceed three separate limits:
The total load limit corresponding to the applicable star rating.
The heating load limit.
The cooling load limit.
The two separate limits are specified in the ABCB Standard for NatHERS Heating and Cooling Load Limits (S42C2(2)). The note says it can be accessed at www.abcb.gov.au. The NCC does not print the numbers, so neither does this guide.
So a star rating on its own is not the whole answer. A design can reach the star band on its total load and still fail, because its cooling load passes the cooling limit. Figure 2 shows the shape of the test.
Climate zone, here and in the checker, is the NCC climate zone defined in Schedule 1 by its Figure 2 and Table 3. Our NCC climate zones guide explains how to find it for an address, and why it is not the same as the NatHERS climate zone the software models.
4. The climate zone 1 and 2 concessions
Table 3 puts Darwin, Cairns and Townsville in climate zone 1, and Brisbane, Mackay and Rockhampton in zone 2. In those two zones only, S42C2(1) offers two lower thresholds.
| Climate zone | Outdoor living area | Star rating required | Clause |
|---|---|---|---|
| 3 to 8 | not relevant | 7 stars | S42C2(1)(a) |
| 1 or 2 | none, or one that fails a test | 7 stars | S42C2(1)(a) |
| 1 or 2 | qualifying, fully covered by an impervious roof of Total R-Value 1.5 or more | 6.5 stars | S42C2(1)(b) |
| 1 or 2 | as above, with at least one permanently installed ceiling fan | 6 stars | S42C2(1)(c) |
The star rating S42C2(1) requires, by NCC climate zone and outdoor living area. Every row also carries the separate heating and cooling load limits.
The outdoor living area must meet every test in S42C2(3):
Where it is. It directly adjoins, and is directly accessible from, a general purpose living area of the Class 1 building, such as a lounge, kitchen, dining or family room. A room for sleeping or for specialist tasks, such as a study or home theatre, does not count (3)(a).
Its size. A floor area of at least 12.0 m² (3)(b), with a length and a width each of at least 2.5 m (3)(c).
Its opening height. At least 2.1 m above floor level (3)(d).
Its open sides. One side permanently open, and a second side either permanently open or readily openable (3)(e).
The sides counted under (3)(e) must be at least 900 mm from an allotment boundary, or 900 mm from an obstruction to the breeze path such as a building, fence or other structure (S42C2(4)). And for either concession the area must be fully covered with an impervious roof with a Total R-Value of at least 1.5, for downward heat flow (S42C2(1)(b), (c)(i)).
Total R-Value is the sum of the R-Values of every layer of a composite element, including materials, insulation, airspaces, thermal bridging and surface resistances (Schedule 1). The 1.5 is therefore a figure for the whole roof build-up over the outdoor living area.
The explanatory notes settle questions that come up on site. The opening height is there to provide a breeze path, and is likely to be measured from the floor to the underside of a perimeter beam. It is not a ceiling height, and not a height for mounting a ceiling fan.
An open side may contain some obstructions, such as columns and barriers. Where an open side needs a 1 m barrier, the type of barrier, wire, solid or other, should be chosen with the overall opening area of the two sides in mind.
The ceiling fan for 6 stars has rules of its own (S42C2(5)). It must be permanently installed, have a speed controller and serve the whole room. A single fan may serve up to 15 m² if its blade rotation diameter is less than 1200 mm, and up to 25 m² if it is 1200 mm or more.
5. The whole-of-home rating
S42C3 is headed net equivalent energy usage. A building must achieve a whole-of-home rating of not less than 60 using house energy rating software.
It answers a different question from the star rating. H6D2 maps the star rating to H6P1, the heating and cooling loads. It maps the whole-of-home rating to H6P2, the energy value of the domestic services. A house can pass one and fail the other, and Option 1 needs both.
The NCC does not set out how the software computes the rating. What it does fix is the scope of H6P2: the domestic services defined in section 1, which include pool and spa pumps and heaters, hot water and on-site renewable energy equipment, and exclude cooking facilities and portable appliances (Schedule 1).
The note to S42C2 points to www.nathers.gov.au for information about building modelling with the software. S42C3 also does not stand alone: S42C4(2) adds Part 13.7 of the Housing Provisions, the services provisions, to the rating pathway (section 6).
6. What else Option 1 requires
A good rating does not excuse the construction details the software cannot see. S42C4(1) adds these Section 13 clauses to S42C2 for H6P1:
| Item | What it requires | Clause |
|---|---|---|
| Insulation installation | Insulation complies with AS/NZS 4859.1, abuts or overlaps adjoining insulation, forms a continuous barrier and does not affect the safe operation of services. Reflective insulation keeps its airspace and is overlapped at least 150 mm or taped. Ceiling bulk insulation overlaps the external wall by at least 50 mm where the wall below has no bulk or reflective insulation. | 13.2.2 |
| Thermal break, roof | Metal sheet roofing fixed directly to metal purlins, rafters or battens, with no ceiling lining or a lining fixed directly to them, needs a break of R0.2 or more between the roofing and its support. | 13.2.3(7) |
| Thermal break, wall | A metal-framed wall in the envelope, with no lining or a lining fixed directly to the frame, and clad in weatherboards, fibre-cement, metal sheeting or the like, needs a break of at least R0.2 at every contact between cladding and frame. | 13.2.5(5) |
| Lost ceiling insulation | Where ceiling insulation is reduced for operational or safety reasons, the loss is made up in the rest of the ceiling to Table 13.2.3w, unless the software has already compensated. | 13.2.3(5); S42C4(1)(c) |
| Slab edge insulation | R1.0 around the vertical edge of a slab with in-slab or in-screed heating or cooling. For other slabs on ground, except waffle pod slabs, R0.64 around the edge in climate zones 6 and 7 and R1.0 in zone 8. The insulation is water resistant and runs from finished ground level to at least 300 mm deep or the full depth of the slab edge. | 13.2.6(4), (5)(a)(i), (5)(b)(i), (6) |
| Building sealing | A damper on the chimney or flue of an open solid-fuel appliance. Roof lights, external doors and openable windows, exhaust fans, ceiling, wall and floor junctions and evaporative coolers sealed where they serve a conditioned space (a heated space, for coolers) or a habitable room in climate zones 4 to 8. | Part 13.4 |
The extra Deemed-to-Satisfy provisions S42C4(1) attaches to the star rating, paraphrased from ABCB Housing Provisions Section 13.
Table 13.2.3w runs from 0.5% of the ceiling area uninsulated to just under 5%, and allows interpolation. A ceiling that needs R4.0, with 1.0% to 1.5% of its area lost to fittings, needs R5.2 in the rest. As the loss grows the table runs out: with 2.0% to 2.5% uninsulated, a ceiling needing R4.5 or more has no permitted value.
Part 13.4 does not apply in climate zones 1, 2, 3 and 5 to a building whose only air-conditioning is an evaporative cooler, or to a permanent ventilation opening a gas appliance needs (13.4.1(2)).
For H6P2, S42C4(2) adds Part 13.7. It covers the insulation of central heating water piping and of heating and cooling ductwork, electric resistance space heating, artificial lighting, the water heater, and swimming pool and spa heating and pumping (13.7.2 to 13.7.9). Lighting is limited to 5 W/m² in the house, 4 W/m² on a verandah, balcony or the like attached to it, and 3 W/m² in an associated Class 10a building (13.7.6(1)).
A pool heater must be solar without electric resistance boosting, use reclaimed energy, gas or a heat pump, or a combination of them (13.7.8(1)).
7. Option 2: the elemental provisions
Option 2 replaces the rating with prescriptive provisions. For H6P1 the house complies with Parts 13.2 to 13.5 (H6D2(1)(b)). The insulation R-Values come from tables indexed by climate zone, and our insulation guide sets them out. Part 13.5 requires ceiling fans to Table 13.5.2 in habitable rooms in climate zones 1, 2 and 3, and in climate zone 5 in New South Wales and Queensland (13.5.2).
For H6P2 the house complies with Parts 13.6 and 13.7, but only if its total floor area is not greater than 500 m² (H6D2(2)(b)). A larger house meets H6P2 with the whole-of-home rating under S42C3, or with a Performance Solution.
Part 13.6 is a calculation. The net equivalent energy usage of the house must not exceed an allowance (13.6.2(1)). In words:
Usage = (floor area factor × efficiency factor) + pool pump usage + spa pump usage − installed capacity of on-site photovoltaics, in kW.
Allowance = floor area factor × energy factor.
The floor area factor is the total floor area multiplied by an adjustment factor from Table 13.6.2a. The adjustment falls as the house grows, from 0.0123 below 50 m² to 0.0075 at 500 m². Total floor area is measured within the inside face of the external walls of the Class 1 building, and includes any conditioned, attached Class 10a building. Between ranges it is rounded up to the nearest whole square metre.
The efficiency factor covers the main space conditioning and the main water heater. It comes from the ABCB Standard for Whole-of-Home Efficiency Factors, not from the NCC. The energy factor in Table 13.6.2b is set by state or territory and climate zone: for example 1.78 in Queensland zone 2, 1.63 in Victoria zone 6 and 2.35 in Western Australia zone 5.
Pools and spas add to the usage. A pool's term is its volume, to the nearest 1000 litres, times a pump factor from Table 13.6.2c, divided by 1000 (13.6.2(2)). The factor depends on the state and falls as the pump's GEMS star rating rises. A spa's term is its volume, to the nearest 100 litres, times a factor from Table 13.6.2d, divided by 100 (13.6.2(3)).
Photovoltaics work the other way. Their installed capacity in kW is subtracted from the usage directly, kilowatt for kilowatt. Part 13.7, services, then applies as it does on Option 1.
8. State and territory variations
NCC 2025 prints variations to Part H6, Specification 42 and Section 13 for three jurisdictions, and smaller changes for two more.
| Jurisdiction | What NCC 2025 prints | Where |
|---|---|---|
| New South Wales | Part H6 of Volume Two, Specifications 42 and 44 and Section 13 of the Housing Provisions do not apply. The variation notes record that NSW Part H6 and Housing Provisions Section 13 of an earlier edition apply instead. H6V2 is deleted. | NSW Part H6, Specifications 42 and 44; NSW 13.1 to 13.7 |
| Northern Territory | Part H6 is replaced. For each of its Performance Requirements, NT H6D2 accepts an energy rating of at least 5 stars using house energy rating software. The alternatives are the NT elemental provisions for fabric, glazing, sealing and air movement (thermal performance) and the NT services provisions (energy usage). Part 13.6 is deleted, so there is no whole-of-home requirement. | NT H6D2; NT 13.6 |
| Tasmania | Part H6 and Section 13 are deleted, and replaced with the energy efficiency provisions of an earlier edition of the Building Code of Australia, named in the variations. | TAS Part H6; TAS 13.1 to 13.7 |
| Western Australia | For an existing house undergoing alterations or an extension, or a new pool at an existing house, the earlier energy efficiency provisions named in the WA note may apply instead of Part H6. For Parts 13.2 and 13.3, climate zone 6 may be treated as climate zone 5. WA 13.2.7 also adds floor insulation in climate zones 4 and 5 where a floor of the house separates it from an attached Class 10a building, and where an upper floor projects beyond the ground floor walls. | WA note to Section H; WA 13.2.1(4), 13.3.1(3), 13.2.7 |
| South Australia | For Section 13, a sunroom or the like is deemed to be a Class 10a building and must comply with 13.2.7. | SA 13.1.2(2) |
| ACT, Queensland, Victoria | No variation to Part H6, Specification 42 or Section 13. | none |
Variations printed in NCC 2025 Volume Two and the ABCB Housing Provisions affecting the house energy efficiency provisions.
9. Check your ratings
Set the NCC climate zone. In zones 1 and 2, describe the outdoor living area if the design has one: its size, opening height, open sides, clearance, roof and ceiling fan. Then enter the star rating and the whole-of-home rating from the NatHERS certificate. The headline gives the star rating the house needs. The gauges compare both ratings with their thresholds, and the cards name every test that fails, with its clause.
10. Worked examples
A Brisbane house with an alfresco. Brisbane is climate zone 2 (Table 3). The alfresco opens off the family room and is 4.5 m by 3.6 m, so 16.2 m². It has 2.4 m to the underside of its beams, two open sides 1.2 m from the side fence, and an insulated roof with a Total R-Value of 1.5. It meets S42C2(3) and (4), so the house needs 6.5 stars.
Add one fan with 1200 mm blades and a speed controller. One such fan may serve 25 m², and 16.2 m² is within that, so the requirement drops to 6 stars (S42C2(1)(c), (5)). A rating of 6.3 stars passes, provided the heating and cooling loads are inside their limits. The whole-of-home rating must still be 60 or more.
The same alfresco with a smaller fan. A fan with blades under 1200 mm may serve only 15 m² (S42C2(5)(c)). At 16.2 m² that fan does not qualify, and the house is back to 6.5 stars. Two such fans, serving 8.1 m² each, restore the 6-star band.
A Townsville deck 4.8 m by 2.4 m. Townsville is climate zone 1. The deck is 11.52 m², under 12.0 m², and 2.4 m wide, under 2.5 m (S42C2(3)(b), (c)). It does not count, and the house needs 7 stars. Widening it to 2.5 m gives exactly 12.0 m², and both tests pass.
A Melbourne house on a slab. Melbourne is climate zone 6, so there is no concession: 7 stars and a whole-of-home rating of 60 (S42C2(1)(a), S42C3). A slab on ground that is not a waffle pod slab needs R0.64 insulation around its vertical edge. It must be water resistant and continuous from finished ground level to at least 300 mm deep, or the full depth of the slab edge (13.2.6(5)(a)(i), (6), through S42C4(1)).
The pool pump on the elemental route. Take a 220 m² house in Queensland, climate zone 2. The floor area factor is 220 × 0.0091 = 2.002 (Table 13.6.2a). The allowance is 2.002 × 1.78 = 3.56 (Table 13.6.2b).
A 50 000 litre pool with a 1-star or unrated pump adds 50 000 × 0.046 ÷ 1000 = 2.30 to the usage. With a 7-star pump it adds 50 000 × 0.012 ÷ 1000 = 0.60 (Table 13.6.2c, Queensland column). The difference, 1.70, matches the credit for 1.7 kW of photovoltaics, which are subtracted kilowatt for kilowatt (13.6.2(1)). The efficiency factor for the heating, cooling and hot water comes from the ABCB Standard, so the full check needs that document.
11. Common mistakes
Reading 7 stars as the whole of S42C2. The heating and cooling load limits are part of the requirement (S42C2(1), (2)). A certificate that reaches the star band but fails a separate limit does not comply.
Counting a covered area that is too small or too narrow. The 12.0 m² and the 2.5 m in each direction are both minimums. A 4.8 m by 2.4 m deck fails both, and the house is back to 7 stars.
Measuring the opening height to the ceiling. The explanatory note says it is likely to be measured from the floor to the underside of the perimeter beam, as a breeze path, and that it is not a ceiling height. A 2.4 m ceiling behind a deep beam can still fail the 2.1 m.
Forgetting the roof. Both concessions need the area fully covered by an impervious roof with a Total R-Value of at least 1.5 for downward heat flow (S42C2(1)(b)). A shade sail or an open pergola is not an impervious roof.
Treating the rating as the end of the job. S42C4 still requires the insulation installation, thermal breaks, slab edge insulation, building sealing and services provisions. None of them is excused by the stars.
12. Where to read the source
NCC 2025 Volume Two Part H6 (H6O1, H6P1, H6P2, H6V1 to H6V3, H6D1 and H6D2), Specification 42, Specification 44, A5G9 and the Schedule 1 definitions are free to read on the NCC website, with ABCB Housing Provisions Section 13 (Parts 13.1 to 13.7) and the state and territory variations. The ABCB Standard for NatHERS Heating and Cooling Load Limits and the ABCB Standard for Whole-of-Home Efficiency Factors are published by the ABCB at www.abcb.gov.au. NatHERS information is at www.nathers.gov.au.
Inside AEC Assistant the Code text is searchable by clause. Ask whether a Brisbane house with a 4 by 3.5 m alfresco off the kitchen can be rated at 6 stars, and the answer comes back with the clause it was read from. This article is general guidance. The building surveyor or certifier for your project determines compliance.
Questions this guide answers
What is the 7 star energy rating requirement for new houses?
Under NCC 2025 a house on the energy rating pathway must achieve an energy rating of at least 7 stars using house energy rating software (Volume Two S42C2(1)). The rating must also meet the separate heating and cooling load limits in the ABCB Standard for NatHERS Heating and Cooling Load Limits (S42C2(2)). In climate zones 1 and 2 a qualifying outdoor living area can lower the requirement to 6.5 or 6 stars.
What is the whole-of-home rating in the NCC?
It is the second number on the energy rating pathway: a whole-of-home rating of not less than 60, produced by house energy rating software (Volume Two S42C3). With Part 13.7 of the Housing Provisions (S42C4(2)), it satisfies Performance Requirement H6P2, which is about the energy value of the house's domestic services. The NCC defines those as heating, air-conditioning, mechanical ventilation, artificial lighting, pool and spa pumps and heaters, heated water systems and on-site renewable energy equipment, and excludes cooking facilities and portable appliances.
When can a house be 6 or 6.5 stars instead of 7?
Only in NCC climate zones 1 and 2, and only with an outdoor living area that meets S42C2(3) and (4) and is fully covered by an impervious roof with a Total R-Value of at least 1.5 for downward heat flow. That gives 6.5 stars (S42C2(1)(b)). Add at least one permanently installed ceiling fan with a speed controller, sized to the area it serves, and the requirement is 6 stars (S42C2(1)(c), (5)).
What counts as an outdoor living area for the NatHERS concession?
A space directly off a general purpose living area such as a lounge, kitchen, dining or family room, with a floor area of at least 12.0 m², both plan dimensions at least 2.5 m and an opening height of at least 2.1 m (S42C2(3)). One side must be permanently open and a second permanently open or readily openable, and those sides must be at least 900 mm from an allotment boundary or an obstruction to the breeze path (S42C2(4)).
Is there a whole-of-home requirement on the elemental route?
Yes, as a calculation rather than a rating. On the elemental route the energy usage requirement is met by Housing Provisions Parts 13.6 and 13.7, for a house with a total floor area of not more than 500 m² (Volume Two H6D2(2)(b)). Part 13.6 compares the net equivalent energy usage of the main space conditioning and water heating, pool and spa pumps, less installed photovoltaics, with an allowance set by floor area, state and climate zone.
Does the 7 star requirement apply in NSW?
No. NCC 2025 prints NSW variations under which Part H6, Specification 42 and Section 13 of the Housing Provisions do not apply, and the variation notes record that NSW Part H6 and Housing Provisions Section 13 of an earlier edition apply instead. The Northern Territory replaces Part H6 with a 5-star rating or its own elemental provisions, and Tasmania replaces Part H6 and Section 13 with earlier provisions named in its variations.
