There are several additional areas in a BASIX multi unit assessment compared to a single dwelling development. In a multi-unit development, you need to address common areas and central systems of the development for all the indices and you need to provide additional specifications for the development. You also have only one option for thermal comfort evaluation in a BASIX multi-unit development assessment which is thermal comfort simulation using a NatHERS accredited software. If you are assessing more than one dwelling for BASIX compliance regardless of the type and specifications of the dwellings, you must select more than one dwelling in the online assessment tool.

You can get a BASIX certificate for multi-unit developments for any number of single detached or attached dwellings, any number of unit buildings with any number of units in each or, in general, any combination of these types in a single BASIX certificate. Since 1st July 2011, a fee must be paid for issuing a certificate which is calculated based on the number and types of dwellings in a development. A table is provided for current fees in effect in our BASIX Certificate Cost page.

If a development has more than 600 units we must contact the NSW Department of Planning, BASIX office to arrange for a special data entry case as the online assessment tool only accepts less than 600 units in each single certificate. You can also divide the development into several sections each with less than 600 units for ease of data entry and also for calculation time since the online assessment tool becomes very slow for a large number of units. The other reason that you might consider dividing a project into sub projects is due to the restrictions in the online assessment tool for building systems like the number of lifts which is restricted to 10. Data entry for a BASIX multi-unit development is performed in 5 separate sections and all sections must be completely filled with the correct type of data before the BASIX multi-unit assessment can be performed and a certificate is generated. These sections are as follows:

  • Address & Type: Enter the project address and building types including number of single detached or attached dwellings and number of unit buildings
  • Details: Enter data related to site specifications, common areas, central systems, unit building and each dwelling specifications in this section
  • Water: Specify water consumption and efficiency measures for common areas and each dwelling in this section
  • Thermal Comfort: Simulation method using a NatHERS Accredited Software is the only authorised method for multi-units and the latest BASIX thermal comfort protocol must be followed in performing the simulation
  • Energy: Energy consumption and efficiency data of the project is entered in this section such as lighting, HVAC, appliance, alternative energy, etc. for central systems, common areas and for each dwelling in the proposed development

In the Summary section, you can get useful hints to improve the sustainability performance of your building if you fail to meet the requirements of BASIX and address the missing data entry elements. The Certificate section will allow you to print Draft report as well as a formal certificate if you have filled all the required fields and passed the BASIX scores for your multi-unit development.

If you have utilised an unusual technology for energy or water efficiency in your development which cannot be addressed by the regular BASIX assessment processes for multi-unit developments, you are able to apply for a BASIX Alternative Assessment under the Certificate section of the BASIX online assessment tool. Any of the the following criteria qualifies a building to follow the path of a BASIX Alternative Assessment:

  • If the building is of a type which cannot be characterized by the interactive online assessment tool
  • Water and energy efficiency measures and technologies in the building are not addressed in the BASIX online tool
  • If the building is of heritage significance and BASIX requirements are in conflict with heritage nature and characteristics of the building

Developments which are planning to be assessed under the BASIX Alternative Assessment method will still be required to meet the sustainability targets for water and energy efficiency and thermal comfort and this approach is only for technologies not currently addressed in the assessment tool.