Every granny flat built in Melbourne since October 2023 has to reach a minimum 7-star NatHERS energy rating under the National Construction Code 2022. That’s a real step up from the old 6-star requirement, and it adds some upfront cost, but it also cuts ongoing bills. This guide covers what compliance actually requires when you build a granny flat, which elements matter most, and how to reach the threshold without overspending on granny flats that don’t need every upgrade available.

What a NatHERS Star Rating Measures

NatHERS calculates a building’s expected annual heating and cooling energy use, based on climate, geometry, orientation, materials and glazing. Melbourne sits in climate zone 6, with cold winters and warm summers, and a 7-star granny flat here needs to keep annual energy loads under roughly 45 to 55 MJ per square metre, depending on layout and orientation. There’s no single way to get there: different combinations of insulation, glazing, orientation and air sealing can all reach the threshold, which gives some flexibility in how you specify a build for energy compliance.

Ceiling Insulation Matters Most

Ceilings see the biggest temperature swings in a home, so ceiling insulation has the largest single impact on a NatHERS score. NCC 2022 sets a minimum of R5.0 for Melbourne’s climate zone, which Innovista’s Affordable package meets as standard, while Signature and Luxe step up to R5.5 or higher for extra margin. Upgrading to R6.0 typically costs $800 to $1,200 and can lift a score by 0.3 to 0.5 stars, useful when other elements are struggling to reach 7 stars on their own.

Wall Insulation and Thermal Bridging

Standard R2.5 wall batts between timber studs only achieve around R2.0 to R2.2 in practice, since heat still transfers through the studs. SIPs construction in Signature and Luxe avoids this with continuous insulation instead, making compliance easier on a less-than-ideal orientation. Luxe’s thermally broken window frames add a further 0.2 to 0.3 stars by cutting cold transfer at the frame.

Glazing and Solar Orientation

NCC 2022 requires a minimum 4-star Window Energy Rating Scheme performance, which all Innovista packages meet with double glazing as standard. Luxe adds Low-E coating, improving scores by 0.3 to 0.5 stars by reducing summer heat gain without blocking useful winter sun. Orientation matters too: north-facing glazing captures winter sun and reduces heating load, so where the granny flat sits on the block, and which way its windows face, directly affects how easily it reaches compliance.

Air Sealing Is Now Mandatory

NCC 2022 introduced mandatory air sealing that didn’t exist under the previous code. Gaps around penetrations, electrical conduits, plumbing, exhaust fans, and joints between wall plates and ceilings let conditioned air escape, undermining even well-insulated construction. Sealing properly adds roughly $1,500 to $3,000. A builder who treats this as part of the standard sequence, rather than an afterthought, avoids the costly remediation that can come from failing an inspection late in the build.

Hot Water System Requirements

Electric resistance hot water systems no longer meet NCC 2022 requirements for new builds. All Innovista packages specify heat pump systems instead, delivering 3 to 4 units of hot water energy per unit of electricity used, cutting running costs by roughly 65 to 70%. Heat pumps cost $1,200 to $1,800 more upfront, but typical annual savings of $400 to $600 recover that within 2 to 4 years.

Costs and savings above are indicative estimates and will vary by site, package and current pricing.

Getting to 7 Stars Without Overspending

The cheapest path to compliance usually combines adequate insulation, sensible glazing and good orientation, rather than maxing out every category. On the Affordable package, confirming a NatHERS assessment before finalising your design helps avoid expensive changes later. Rotating a floor plan 15 to 30 degrees can sometimes lift a rating by 0.3 to 0.5 stars at no extra cost.

For granny flats that’ll be lived in full-time, it’s often worth exceeding the 7-star minimum. According to Sustainability Victoria, 7-star homes typically use 20 to 25% less heating and cooling energy than 6-star homes, and that gap only grows the higher you go, so the extra comfort and lower bills tend to justify a modest upgrade over the bare minimum.

Your Next Steps

Book a free site assessment where we go through orientation options and construction specifications for cost-effective 7-star compliance on your block, or explore our G-Flat™ packages to compare standard energy specifications.

FAQs

Do all granny flats in Melbourne need a 7-star energy rating? Yes. Since October 2023, every new granny flat in Melbourne must meet a minimum 7-star NatHERS rating under NCC 2022, replacing the previous 6-star minimum.

What adds the most cost when you build a granny flat to 7-star standard? Air sealing and any glazing or insulation upgrades tend to add the most, though orientation and design choices can reduce how much extra spec is needed to reach compliance.

Is NCC 2022 energy compliance the same across all of Melbourne? Melbourne falls within climate zone 6 for NatHERS purposes, so the target energy load is broadly consistent across the metro area, though your specific site and orientation still affect what’s needed to reach it.

Contact Innovista Group to review NatHERS results for your granny flats floor plan and orientation before finalising your design.