Alteration and additions

.

Documentation requirements

If the thermal loads meet the criteria described in the Modelling Process section, you will need to collect the following documentation:

  • the simulation output generated by Approved Software for the existing, reference, and proposed models;
  • a record of all assumptions made about the building fabric of the existing dwelling, signed by the applicant;
  • supporting evidence such as a letter from council, an engineer's report or a letter from the building or strata manager;
  • plans and specifications for the proposed work; and
  • photos of the existing dwelling.

The required simulation outputs from the existing and reference models are the interim/diagnosis reports and building data reports from the simulation software and/or the online system from the software provider.

The required simulation output from the proposed model is the NatHERS universal certificate issued from the online generation system by the software provider.

 

Previous: Modelling process                   

Modelling process

The modelling process for alterations and additions is much more involved than for a new dwelling. You will need to run three separate simulations:

  1. Existing: model the existing dwelling, and document all assumptions about the thermal performance of the existing building fabric.

  2. Reference: model the entire existing dwelling and the alterations and additions, with all new work complying with the relevant BASIX Construction and Glazing commitments. You must not change the assumed performance of the existing building fabric.

  3. Proposed: model the entire existing dwelling and the alterations and additions, but with the actual proposed performance for the new building elements. Only change the performance of the parts of the existing building fabric where new work is being done such as installing additional insulation or replacing a window.

This diagram shows what will need to be included in the simulations of the existing, reference and proposed models. This is also explained in the article text.This diagram shows what will need to be included in the simulations of the existing, reference and proposed models.

You will need to demonstrate that the alteration or addition does not reduce the overall thermal performance of the dwelling, and that the proposal performs at least as well as if it had been in accordance with the BASIX Construction and Glazing commitments. That is:

  • the total loads calculated for the proposed model must be less than or equal to the total loads calculated for the existing model; and
  • the total loads calculated for the proposed model must be less than or equal to the total loads calculated for the reference model.

 

Previous: Application process                   Next: Documentation requirements

Application process

Before you start running simulations, we recommend that you contact the BASIX helpdesk to check whether Simulation will be permitted for your project.

To use Simulation for your alterations and additions project:

  1. Identify clearly why you believe that your project cannot fully comply with the BASIX Construction and Glazing commitments. At this stage, Simulation for alterations and additions is not available for:
    • design flexibility in the absence of specific heritage, structural or legal restrictions; or
    • purely aesthetic reasons.
  2. Contact the BASIX helpdesk and request permission to use Simulation for your alterations and additions project. You will be required to justify your request.

  3. If the BASIX helpdesk advises that you may use Simulation, run the Simulations in accordance with the following section.

  4. Once you have completed the Simulations and demonstrated acceptable thermal performance, submit the documentation to the BASIX helpdesk. The documentation required is listed in the final section of this guide.

  5. If the analysis and documentation is satisfactory, you will be given further instructions on how to apply for Alternative Assessment.
Previous: Using simulation for alterations and additions               Next: Modelling process

Using simulation for alterations and additions

These pages describe the process for applying to use Simulation for alterations and additions projects. You should familiarise yourself with the:

  1. Application process
  2. Modelling process
  3. Documentation requirements.

 You can also download this information as a PDF: BASIX Guide: Using Simulation for Alterations and Additions.

Simulation can allow greater design flexibility by trading performance between new building elements, and may be appropriate in situations where there are practical or legal constraints preventing full compliance with the BASIX requirements for alterations and additions. This could include:

  • heritage considerations
  • structural limitations
  • strata restrictions in unit buildings.

This guide does not cover situations where a construction type or product type is not available in the drop-down selections. Check with the BASIX helpdesk and they will be able to help you determine if you are eligible to use the Alternative Assessment process.

 Next: Application process

Alterations and additions

BASIX applies to all Alterations and additions in NSW that are valued at $50 000 and over and/or involve the installation of a pool and/or spa with a total volume greater than 40,000 litres.

The BASIX assessment tool has a section specifically designed for alterations and additions to existing homes. This section differs slightly from the single dwelling and multi-dwelling sections of the tool in that there are no set reductions for energy or water.

Instead the tool aims to reduce potential water consumption and emissions by encouraging efficiency improvements. The alterations and additions section of the BASIX assessment tool:

  • Reduces the energy required to heat and cool homes through improved glazing, insulation, building design and construction materials
  • Requires at least 40% of new or altered light fixtures to be fitted with high efficiency globes
  • Promotes the installation of solar, gas, heat pump or wood systems instead of high emission electric hot water systems
  • Requires all new taps, toilets and showerheads have a minimum efficiency rating of 3 WELS stars
  • Reduces pool and spa emissions by phasing out high emission electric heating systems
  • Reduces water consumption in pools and spas by encouraging rainwater tanks and covers to reduce evaporation

If the alterations and additions are valued at $50 000 and over and are not for use as a dwelling (or capable of being used as a dwelling), you need to check with your local council if BASIX applies.

Subcategories