La Perouse Coastal Duplex
Detailed NatHERS thermal modelling for a coastal duplex in La Perouse, Sydney, designed with an approximately 60% glazing ratio to capture natural light and ocean views — without compromising energy performance.
Project Details
- Location: La Perouse, Sydney NSW
- Project Type: Duplex residential development
- Design Feature: High glazing ratio (approx. 60%)
- Services: NatHERS Thermal Modelling + Energy Assessment
- Exposure: Coastal — direct ocean-facing orientation
Project Overview
This duplex project in the coastal suburb of La Perouse, Sydney, presented a genuinely challenging architectural brief: large glazing areas and open living spaces designed to maximise natural light and capture ocean views, across two attached dwellings with different orientations.
Coastal sites like this one add a layer of complexity that inland projects don’t face — higher wind loads, salt-laden air affecting frame and glazing specification, and a design brief that leans even harder into glass to make the most of the outlook. All of that had to be reconciled with NSW’s energy compliance requirements.
Project Description
Homes with high glazing percentages can experience significant heat gain during summer and heat loss during winter, making energy compliance more challenging than a typical low-glazing design. This duplex’s approximately 60% glazing ratio, spread across multiple façades, meant thermal performance couldn’t be left to chance — it required detailed, façade-by-façade thermal modelling rather than a standard assessment.
As a duplex, the project also needed each dwelling assessed and rated individually, since NatHERS and BASIX requirements apply per dwelling, not to the development as a whole. Each unit’s different orientation and glazing exposure meant the two dwellings needed separate optimisation strategies to both reach compliance.
Our team conducted a full NatHERS assessment, analysing:
- Solar heat gain across each glazed façade
- Shading conditions from the building form, neighbouring structures, and any proposed shading devices
- Insulation levels across walls, roof, and floor
- Glazing performance — U-value and SHGC (solar heat gain coefficient) for each window and door specification
- Orientation-specific performance differences between the two dwellings
Through careful optimisation of the building envelope and window specifications — rather than a blanket downgrade of the glazing design — we were able to improve the thermal performance of both dwellings while preserving the architect’s design vision and the ocean outlook the whole brief was built around.
Why Coastal Projects Need Extra Modelling Care
Coastal duplexes and homes bring a few additional variables into the thermal modelling that inland projects don’t need to account for:
Wind exposure: Higher and more consistent wind speeds affect infiltration modelling and can change the effectiveness of natural ventilation strategies used to offset glazing loads.
Salt air and glazing specification: Frame and glazing material choices in coastal zones often need to balance durability (corrosion resistance) with the thermal performance figures used in the NatHERS model — the two don’t always point to the same product by default.
Orientation sensitivity: Ocean-facing glazing is often oriented for the view first and thermal performance second. Modelling has to work with that fixed orientation rather than recommending a re-orientation that would defeat the purpose of the design.
Reflected glare and heat: Large water surfaces can increase reflected solar radiation onto glazed façades, which is factored into shading and glazing recommendations.
The Result
The final thermal modelling outcome demonstrated that even architecturally ambitious homes with large glazing areas can achieve strong sustainability outcomes when supported by accurate, façade-specific energy modelling:
- Both dwellings achieved compliant NatHERS ratings despite the high glazing ratio
- The architect’s design intent — maximising light and ocean views — was fully preserved
- No blanket reduction in glazing area was required
- A coordinated envelope and glazing strategy addressed both dwellings’ distinct orientations
Key Features
- Coastal duplex development
- High glazing ratio design (approx. 60%)
- Advanced, façade-by-façade NatHERS modelling
- Optimised building envelope performance
- Individually assessed and rated dwellings
- High energy efficiency outcome without redesigning the glazing
Frequently Asked Questions
Can a home with 60% glazing still pass NatHERS?
Yes — as this La Perouse project shows, high glazing ratios are achievable with detailed, façade-specific thermal modelling and the right combination of insulation, shading, and glazing specification. It typically requires more modelling iterations than a standard low-glazing design, not a reduction in glass area.
Does each dwelling in a duplex need its own NatHERS rating?
Yes. NatHERS and BASIX assessments apply per dwelling, so a duplex needs two separate assessments — one for each unit — even where they share a common wall and were designed as a single development.
Do coastal locations affect NatHERS thermal modelling?
Indirectly, yes. While NatHERS climate zones are location-based, coastal conditions such as wind exposure and reflected heat from water can influence the shading, ventilation, and glazing strategy needed to achieve compliance.
What's the difference between NatHERS and BASIX for a duplex development?
NatHERS rates each dwelling’s thermal performance on a 0–10 star scale. BASIX is the NSW planning requirement covering water and overall energy use for development approval. Duplex developments in NSW generally need both, assessed per dwelling.
Why Choose EcoMaxHomes?
- Deep expertise in BASIX and NatHERS compliance across NSW, including multi-dwelling and duplex developments
- Proven ability to model and resolve high-glazing, coastal, and complex-orientation projects
- Individually optimised strategies for each dwelling, not a one-size-fits-all approach
- Fast turnaround times for approvals
Ready to Start Your Project?
If you’re planning a coastal home, duplex, or multi-dwelling development in Sydney or NSW and want expert thermal modelling that protects your design intent, Ecomaxhomes can help.
Our team will help you meet compliance requirements while preserving your design vision.