So what is BASIX?

BASIX: What NSW Homebuyers Need to Know

If you're building a new home in New South Wales, you've probably heard of BASIX—the Building Sustainability Index. Introduced by the NSW Government, BASIX is a mandatory sustainability assessment tool designed to reduce water usage, energy consumption, and greenhouse gas emissions in residential buildings. It’s a fantastic initiative for the environment and long-term savings—but many people who are going to build their new home do not realise that builders are leaving essential BASIX items out of their pricing.

To meet BASIX standards, new homes must include a range of sustainability features. These can vary depending on location and design, but commonly include:

  • Increased insulation in walls and ceilings(even garage walls)

  • Double-glazed windows or improved window performance

  • Ceiling fans in living areas and bedrooms

  • Solar panels or energy-efficient hot water systems

  • Rainwater tanks increased in size

  • Repositioning of the home on the block

These features help homes achieve better thermal comfort and energy efficiency, often reaching a 7-star rating under the Nationwide House Energy Rating Scheme (NatHERS)2.

The problem is: some major builders are not including BASIX requirements in their advertised build prices. Instead, they present a base price that looks attractive—until the buyer signs the contract and discovers they need to fork out an additional $10,000 or more to meet BASIX compliance.

The result? Homeowners are blindsided by unexpected costs during the approval process, often when it’s too late to renegotiate or change builders.

What You Can Do to Protect Yourself?

Ask the question(before you sign anything)- does my price include everything that is needed to pass a Basix assessment? you want to make sure you are not going to be charged extra , if the insulation ,for example, needs to be upgraded.

BASIX is a powerful tool for creating greener, more efficient homes—but it shouldn’t be a financial trap. Builders have a responsibility to be transparent, and buyers deserve to know what they’re signing up for. By staying informed and asking the right questions, you can avoid costly surprises and build a home that’s both sustainable and budget-friendly.

And if you need further advice , Carnelian’s Tender health Check can help, we look over your Build Contract or Tender and let you know exactly what is or isn’t included in your price.

Kerri-Ann Hooper