BASIX for Dual Occupancy Developments in NSW

Dual occupancy, the duplex, is one of the most common ways to add value to a NSW block. From a compliance angle a duplex is two homes, and BASIX treats it that way. Here is what that means and how to design a duplex that passes cleanly.

Two dwellings, two sets of targets

Each dwelling in a dual occupancy must meet the BASIX energy, thermal comfort and water targets. They can be covered on a coordinated certificate, but each home is assessed on its own merits, including its own NatHERS rating.

The orientation challenge

The classic duplex problem is orientation. On a typical block, the two dwellings often face opposite directions, so one gets favourable north access and the other does not. The less favourable side needs more attention to shading, glazing and insulation to reach the same standard.

• Mirror plans thoughtfully. A simple mirror can leave one dwelling with poor solar access.
• Tune each side. The shaded or west-facing dwelling may need better glazing or roof colour.
• Shared walls help. The common wall reduces external surface area, which can aid both dwellings.

Party walls and acoustics

The shared wall between dwellings reduces heat loss through that face and contributes to comfort. It is one of the quiet advantages of attached housing for energy performance.

Keeping the project efficient

Assessing both dwellings together avoids duplication and keeps the documents consistent. We model each home, tune the harder-oriented side and deliver coordinated BASIX and NatHERS certificates for the whole development.

Frequently asked questions

Can one certificate cover both dwellings? The project is documented together, but each dwelling must satisfy the targets in its own right.

Why does one side rate lower? Usually orientation. We adjust the design of the less favourable dwelling to match.

Building a duplex? Send us the plans for a coordinated dual occupancy assessment.