Green Star Buildings: How to model in eTool

Green Star has launched a new rating system – Green Star Buildings. The Positive category acknowledges the value in understanding the full lifecycle impacts of the buildings which in turn can lead to better low carbon designs.

In this article, we highlight the main points of difference compared to other Green Star rating versions to help you model your LCA in eTool for your Green Star Buildings submission.

Jump to the following sections in this post:


Setting Up Your Project for Green Star

For the basics on how to set up your project for Green Star, please click on the link below. The rest of this post covers the details of where Green Star Buildings varies from other Green Star versions.

Green Star Project Set Up

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Decarbonisation of Future Grids

According to the Green Star Buildings Submissions Guidelines, decarbonisation of future grids may be taken into account in the study for buildings with a design life of 60 years or more.

For the convenience of our users, we have recently added these grids in eTool. In the Project level under the ‘Site Attributes’ tab, you can now select a range of regional ‘Decarbonised Green Star’ 2020 grids for your project. Note that these grids have environmental discount factors applied to adjust for potential future impacts which does not align with EN15978 standards. This will not prevent your design from getting certified, however associated quality checks will be left in question to highlight the misalignment.

Please use the same decarbonised grid for both default import & export grids.

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Construction Specifications for the Reference Design

For Green Star Buildings, there is now a prescriptive list of construction specifications for the Reference Design in the ‘Upfront Carbon Emissions Calculation Guide’. Please note that the onus is on the lead author to ensure that their study aligns with the GBCA’s detailed specifications. Our reviewers are not responsible for ensuring that the Reference Design’s specifications align with those outlined in the Green Star Buildings’ guide. By default, we always review against the EN15978 standards.

Note: Type the keyword ‘GSB’ in our Template Library browser to find the public templates with specified default material types by GBCA for use in a Reference Design.

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Solar PV Systems & Renewable Energy Generation

For Green Star Buildings, you are now allowed to model solar panel systems in the Reference Design to address the issue of the higher upfront carbon impact associated with having the system in the Proposed Design without compromising your points.

Note that according to EN15978 any energy generated that is exported to the grid should be reported under LC module D1 (refer to this post on how to model that in eTool). However Green Star Buildings excludes any energy exported to the grid. Therefore we recommend that you report all energy generated to LC module B6 instead to avoid losing GS points.

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Data Sources & EPDs

Special consideration needs to be given to the types of LCA data used in an LCA. There are 2 types of LCI data applicable for materials/products: process or hybrid. Both data types should not be mixed together for the same product or element. EPDs and all of the eTool default LCI sources are process LCA data. This means that both EPDs and the eTool default data can be used interchangeably for products and elements.

When modeling EPDs in your study, please ensure that the LCI source used in the EPDs are consistent with the rest of your study to ensure alignment with EN 15978. Attention must also be given to making sure that the characterisation factors used in the EPDs are aligned with EN15804.

For more information on the different types of data, please download and read this article: LCI Data.

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Modeling Carbon Neutral Products

Please note that you are now allowed to include carbon neutral products for Upfront Carbon points in Green Star Buildings. For guidance on how to model carbon neutral products in eTool, please refer to the support post below:

Modeling Carbon Neutral Products in eTool

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Upfront Carbon Reporting in eTool

We always recommend our users to model their LCAs to best practice whole building/structure EN15978 standards. However for Green Star Buildings, up to 6 points are up for grabs when you report on upfront carbon emissions. We plan to make upfront carbon reporting available in eTool at some point in the future but in the meanwhile, we have created the spreadsheet below for our users to download & use for their submission instead.

>>Download Green Star Buildings LCA Points Calculator<<

(file updated 21/02/2024)

*Latest version of the spreadsheet has been updated to better account for negative biogenic emissions without zeroing out other negative material impacts. Therefore you can now also use the ‘Negative’ material method to model carbon neutral products.

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Negative Biogenic Carbon

Responsibly sourced bio-based materials can claim a Global Warming Potential Total (GWPT) of 0 under modules A1-A3 for the Upfront Carbon Emission credit in the Life Cycle Impacts calculator. However, benefits from the negative biogenic carbon can then be reported for all modules A-D in the selected data source for the Life Cycle Impacts calculator. The GBCA intend to review and update the Life Cycle Impacts calculator on the Green Star online platform to facilitate this.

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End-of-Life Demolition Impacts of Existing/Previous Building

In Green Star Buildings, they’ve introduced this criteria for situations where the impacts of demolishing the existing/previous building is taken into account when it is less than 50 years old.

In line with GBCA recommendations, we suggest that users take advantage of our ‘target setting’ whole building/structure templates to model the existing building by using gross floor area and business-as-usual specifications. If you use the search term ‘TS’ you will find a large selection of whole building templates that you can use to quickly construct a generic version of the existing building to calculate the embodied carbon impacts. Note that some of the templates require areas such as carparks to be added separately. The material impacts of mechanical equipment/appliances will also need to be added in separately for a more complete whole building LCA.

Should you need to submit the existing/previous building design for Certification, we recommend that you model the design as a separate Structure within the same Project. Please ensure that you provide the following information:

  • Explain in detail the purpose and any assumptions used for the building’s construction specifications of the Design in the Structure level description
  • Update the target construction & operational scope in the Structure level as appropriate
  • Use ‘Scenario’ as the Design purpose
  • Remember to include the appropriate end-of-life demolition templates for the building to account for those impacts
  • Provide supporting documentation for the Commissioning date as this will be evidence for the Predicted Service Life of the building
  • Upload any other supporting documentation where possible to help the reviewer complete the review

Please note that the review will be conducted to EN 15978 standards, therefore a number of quality checks may be left in question to highlight any deviation from the standards.

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