In December 2022, the Green Building Council of Australia (GBCA) released an interim document: Upfront Carbon Emissions calculation guide – interim. Guidance on calculation methods for the Upfront Carbon Emissions and Life Cycle Impacts credits.

The purpose of the guide is to outline the proposed method of measuring upfront carbon emissions for Greenstar registered projects. Whilst its status is interim, the paper indicates to the industry how the GBCA will treat carbon measurement.

Upfront carbon is defined as the carbon emissions caused during manufacture and transport of building products before construction begins.  In the article, the GBCA have provided an overview of how upfront carbon will be considered and how the industry can model a project’s upfront carbon emissions.  A Green Star registered project will compare carbon reduction against typical Australian buildings.

Two accepted methods for calculating upfront carbon emission reductions have been proposed:

1. Comparison against a fixed benchmark;

2. Comparison against a Reference Project (GBCA, 2022, p.8).

For projects considering Greenstar ratings the building owner will need to measure the proposed project against one the above options, with scores being assigned by GBCA as follows:

“Any project seeking to get a rating under Green Star Buildings must reduce its upfront carbon by at least 10% (Minimum Expectation).  Those seeking higher ratings must achieve at least a 20% reduction (Credit Achievement worth 3 points).  Over time, the requirements increase to have all future registered projects to meet a 40% reduction (Exceptional Performance worth an additional 3points).(GBCA, 2022, p.7).

The intent of the upfront carbon emissions calculation guide is to assist project teams and allow for industry use, testing and feedback. The guide will be superseded in 2023.

 1.      Comparison against a fixed benchmark

The first method proposed by the GBCA is comparison against a fixed benchmark (currently under development).  

The “GBCA and NABERS are collaborating on developing an aligned method for calculating upfront carbon emissions reductions against a fixed benchmark. This is expected to be released in late 2023. A consultation process will be running from December 2022 to February 2023. Upon the release of this aligned method and fixed benchmarks, GBCA will amend Green Star Buildings to allow for such method to be accepted...” (GBCA, 2022, p.10).

The benchmark declared unit for upfront carbon emissions is kg CO2e/m2 GFA, which is kilograms of carbon dioxide equivalent per square metre of Gross Floor Area (GFA). (GBCA, 2022, p.8).

Subsequently, if a Greenstar registered projects chooses the fixed benchmark method, it will be required to calculate total upfront carbon emissions and demonstrate a reduction against (to be determined) fixed benchmarks.

 2.      Comparison against a Reference Project

The second method (comparison against a Reference project) requires two sets of upfront carbon emissions calculations: one for the Proposed Project and one for the Reference Project.

The GBCA note “The Proposed Project is defined as the project as designed and built by the project team. A Reference Project is a hypothetical project of the same size, shape, location, floor area and glazing areas as the Proposed Project.”

The Proposed and Reference Project must share the same:

• Life cycle stages and system boundary

• Calculation methodology

• Data sources and data hierarchy

• Declared units

• Site work boundary

• Building elements boundary

• Size, scale, volume, and function

• Shared elements

• Cut-off rules

• Assumptions on carbon sequestration, carbon neutral products, and carbon offsets

• Considerations for demolition and reuse of existing buildings (GBCA, 2022, p.8).

GBCA highlight the following differences between the Reference and Proposed Project will be considered to show reductions:

• Reusing existing building elements or site infrastructure

• Improvements through iterative design processes

• Building material choices and quantities

• Transport emissions

• Construction emissions (GBCA, 2022, p.8).

 Data sources and data hierarchy

Two types of data are needed to complete a carbon emissions calculation:

1. Building Quantities

2. Emissions factors

Calculating Building Quantities whilst onerous, is well understood by the industry.

Emissions factors on the other hand are the new kids on the block and will present a set of challenges to the industry. Additionally, the GBCA propose the following hierarch must be used for emission factors:

1. Product-specific emissions factor based on specific Environmental Product Declaration (EPD) – where available

2. Generic value from database

3. Generic value from a global literature scan

A significant concession to the above hierarchy is the GBCA propose to allow a mix of data sources within a calculation, however the same data source for the Proposed and Reference Projects must be applied to the same building element (e.g. structural framing).

 Default specifications

The GBCA have included default materials and specification for use in the Reference Project for the following building types:

• Mid to high rise buildings

•  Warehouse buildings

• Low rise buildings

• Residential buildings

The guide includes a high-level material and specification for each building element (for example structural elements indicate concrete strength and reinforcement ratios).

The exciting take-out of the default specification is the framework is in place to start modelling. The following process is laid out:

1.    develop designs between a Proposed and Reference Project

2.    calculate the quantities

3.    apply emission factors

4.    compare total carbon for each option

5.    forecast the percentage reduction in carbon

Closing thoughts

Whilst the built environment has caused considerable impact on the natural environment, our industry can be part of the solution. Carbon planning during the early design phases will lead to significantly improved environmental design decisions and the GBCA have now provided the methodology for the industry to respond.

Key takeout from the GBCA is two calculations methods have been identified by the GBCA:

• Method 1 - Comparisons against fixed benchmark will not be available until late 2023 subsequently the industry will remain on standby regarding the viability of this method.

• Method 2 – Comparison against a Reference Project can now be considered by the industry.

  • A single source of Carbon emission factors for Australia is not yet available and the industry will rely on multiple sources for calculations.

  • The data source for carbon factors must be consistent across elements between the Proposed and Reference Project.

Carbon Planning is available now

Cost Group is excited to announce we have structured our cost planning database for carbon emission calculation. We can concurrently advise capital costs and upfront carbon emissions; seamlessly and efficiently.

Before undertaking detailed and expensive design, Cost Group can model the carbon emissions based on conceptual design information considering various design alternatives.  This provides for informed design decisions to either meet Greenstar requirements; or simply maintain good corporate governance.

If your project is considering the impacts of carbon emissions or you would like to discuss any matters in this post, please leave a comment or contact me at murray.baker@costgroup.com.au.

Reference

Greenstar (2022). Upfront Carbon Emissions calculation guide – interim.  Guidance on calculation methods for the Upfront Carbon Emissions and Life Cycle Impacts credits. www.gbca.org.au

murray.baker@costgroup.com.au

Expertise: carbon planning, cost planning, bills of quantities.