Eastgardens Duplex
A duplex residential development in Eastgardens, Sydney, achieving a 7-Star NatHERS rating across both dwellings through coordinated envelope design and individual per-dwelling assessment.
Project Details
- Location: Eastgardens, Sydney NSW
- Project Type: Duplex residential development
- Services: NatHERS Assessment + BASIX Certification
- Energy Rating: 7-Star NatHERS (both dwellings)
Project Overview
This duplex development in Eastgardens, in Sydney’s eastern suburbs, needed to meet the 7-Star NatHERS minimum that applies to new homes across most of NSW under NCC 2022 — a straightforward-sounding target that becomes more involved on a duplex, where two attached dwellings with their own orientation, layout, and glazing need to be assessed and optimised individually rather than as a single building.
Why Duplex Developments Need Individual Attention
A duplex looks like one building from the street, but for NatHERS and BASIX purposes it’s treated as two separate dwellings, and that has real design implications:
Two individual assessments: Each dwelling in a duplex is rated on its own, so both units need to independently reach 7 stars — a shared wall and a shared roofline don’t average out a weaker-performing unit against a stronger one.
Different orientations, different strategies: The two dwellings in a duplex often face different directions or have different levels of solar exposure depending on the site layout, which means the glazing, shading, and insulation strategy for one unit doesn’t automatically transfer to the other.
Shared elements, individual outcomes: Party walls and shared structural elements need to be modelled correctly for each dwelling’s own thermal performance, rather than assumed to behave identically on both sides.
Our Approach
The Ecomaxhomes team carried out a full NatHERS assessment for each dwelling, covering:
- Insulation performance across external walls, roof, and flooring systems for both units
- Glazing specification (U-value and solar heat gain coefficient) suited to each dwelling’s specific orientation
- Shading design to manage solar heat gain on the more exposed of the two dwellings.
- Coordination between the two assessments to ensure both dwellings reached compliance without one unit’s design compromising the other’s performance
The Result
- Both dwellings achieved a 7-Star NatHERS rating, meeting the NCC 2022 mandatory minimum
- Each unit’s design was optimised individually rather than assessed as an average across the development
- The duplex’s architectural design and layout were preserved without requiring redesign
- A coordinated, efficient certification process across both dwellings
Key Features
- Duplex residential development
- 7-Star NatHERS rating achieved for both dwellings
- Individual, per-dwelling thermal assessment
- Orientation-specific glazing and shading strategy
- Coordinated envelope design across shared elements
Frequently Asked Questions
Does a duplex need two separate NatHERS ratings?
Yes. NatHERS and BASIX assessments apply per dwelling, so a duplex needs two individual assessments — one per unit — even though the two dwellings share a wall and are built as a single development.
Can one dwelling in a duplex have a different rating to the other?
Yes, and in practice this is common. Different orientations and layouts mean each dwelling in a duplex can have a different energy performance outcome, which is why each unit needs its own glazing and shading strategy rather than a single shared approach.
What does a 7-Star NatHERS rating mean?
NatHERS rates a home’s thermal performance on a 0–10 star scale. Since October 2023, most new homes across NSW must meet a 7-Star minimum under NCC 2022, alongside a whole-of-home energy budget.
Is BASIX required as well as NatHERS for a duplex in NSW?
Yes. NSW duplex developments generally need both a NatHERS assessment for thermal performance and a BASIX certificate covering water and overall energy use, assessed per dwelling.
Why Choose EcoMaxHomes?
- Deep expertise in BASIX and NatHERS compliance across NSW, including duplex and multi-dwelling developments
- Individual, per-dwelling assessment rather than a single averaged approach
- Coordinated strategies that keep both dwellings’ design and performance aligned
- Fast turnaround times for approvals
Ready to Start Your Project?
If you’re planning a duplex or multi-dwelling development in Sydney or NSW and want a coordinated, efficient path to compliance for both dwellings, Ecomaxhomes can help.
Our team will help you meet compliance requirements while preserving your design vision.