Please note: as of 5/8/2025 our recommendation on how to report on impacts per GFA for Green Star using supporting functions has been updated. Please refer to the Reporting For Green Star section below or contact us for support if you require further clarification.

This is a supplementary post that explains in further detail how Primary & Supporting Functions work.

The main purpose of the Functions feature in eTool are to:

1. Report impacts prescribed only to a particular function
2. Enter customised Services, Characteristics, Floor Areas and Functional Unit parameters for each function which can then be referenced by expressions in formulas used in the Design and during automated report generation.

Each Design can contain an unlimited number of functions and each function can be set either as a ‘Primary’ or ‘Supporting’ function.

When modeling in eTool, you assign elements & templates to the “whole asset/building” or to different functions. When calculating impacts in the design, they’ll be reported against these functions. The functions contain measurable attributes used for calculations & reporting (GFA, Occupancy, etc).

Primary Functions – When running reports, Primary Functions are all able to be assessed independently from the “Whole Asset” in order to report on a subsection within a design. Their impacts and attributes are used when producing results (e.g. Total kgCO₂ per m² Gross Floor Area by function). 

Supporting Functions – These functions are not assessed independently. When present in a design, their impacts and attributes are apportioned across all of a design’s Primary Functions. When running a report on the “Whole Asset”, all of the design’s impacts and functional attributes are included.

Generating LCA Report with ‘Whole Asset’ as Focus

 

Example:

Primary function 1 Residential: 100m² GFA. 1,000 kgC0₂
Primary function 2 Commercial: 100m² GFA. 1,000 kgC0₂
Primary function 3 Mixed Use: 100m² GFA. 1,000 kgC0₂
Supporting function Carpark: 50m² GFA. 1,000 kgC0₂

‘Whole Building’ selected as object of assessment will result in total design impacts of 4,000 kgC0₂ or 11.4 kgC0₂ per m² GFA.

Generating LCA Report with a ‘Primary Function’ as the Focus

When a Primary Function is selected as the main object of assessment, the total impacts will include the selected Primary Function impacts + a portion of the Supporting Function’s impacts. This portion is based on the selected Primary Function’s proportion over the total Primary Function GFAs.

Example:

Primary function 1 Residential: 100m² GFA. 1,000 kgC0₂
Primary function 2 Commercial: 100m² GFA. 1,000 kgC0₂
Primary function 3 Mixed Use: 100m²GFA. 1,000 kgC0₂
Supporting function Carpark: 50m² GFA. 1,000 kgC0₂

Object of Assessment: Primary function 1 Residential, total impacts will be 1,333 kgC0₂.

1,333 kgC0₂ = Primary function 1 Residential impacts 1,000 kg C0₂ + apportioned supporting functions impacts 333 kgC0₂ (1,000 kgC0₂ x (100 m² / 300 m²)).

 

Generating LCA Report with ‘Primary Function’ as Focus using per m² Gross Floor Area  

When selecting impacts per Gross Floor Area (GFA) m² as the function, the total reportable GFA will be based on the selected Primary Function GFA plus a portion of the Supporting Functions total GFA. Using the above example, if selecting Primary Function 1 Residential as the object of assessment, total reportable GFA will be 116.7m².

Example:

116.7m² = Primary function 1 GFA (100m²) + apportioned Supporting Function GFA (16.7m²)

Apportioned Supporting Function = (100m² GFA Primary Function / 300m² GFA total Primary Function) x 50m² GFA Supporting Function.

 

Supporting Function when using per m2 Gross Floor Area

The Supporting Function impacts will be apportioned according to the selected Primary Functions proportion of total Primary Function GFA, and as described above, if reporting per m² GFA, divided by the apportioned total m² GFA.

NOTE: When reporting in per m² GFA, if any of the Primary Functions have zero GFA or no GFA as an input field (i.e. ‘Rail Bridge’ function), the supporting function impacts will be automatically divided equally among the number of design Primary Functions.

 

For Green Star Reporting

For Green Star, their definition for GFA excludes any car parking (including undercover car parking) areas however the associated impacts for the carparks must still be accounted for in the study. Therefore, reporting for Green Star based on per m² GFA isn’t straight forward.

You can consider using the following methods depending on the type of carpark:

Open Air Carparks

Use the ‘Roadway’ function for open air carparks. You can still record the floor area of the carpark under ‘pavement area’ for transparency, however this won’t contribute to the total GFA when reporting. Note that if you have any templates assigned to this function that uses the ‘GFA’ expression in it’s calculation formula, those calculations won’t work properly anymore as there won’t be a ‘GFA’ for this function.

Enclosed Underground Carparks

For enclosed underground carparks, the correct function to use should be the ‘Automobile Parking Facility’ function. As you can see, this function has GFA as an input field.

For this carpark type, you have 3 methods to go about modeling it:

Method 1 – No Carpark Function

1. Do not add a carpark function (i.e. only one primary function for the whole building)
2. Exclude carpark areas in the primary function’s GFA
3. In the Structure Level Description, explain Green Star’s definition of GFA and note the missing GFA for carparks for the reviewer’s reference
4. Generate the report as per normal.

Downsides: Need to check and update any carpark inputs/templates in the design with expressions that specifically references carpark GFA.

Method 2 – Reporting on NLA

1. Set the carpark function as the Supporting Function
2. Fill out Net Lettable Area (NLA) for the Primary Functions to be the same as the GFA (as per Green Star definitions) but leave the carpark NLA as zero.
3. Generate report based on m² NLA instead of GFA with ‘Whole Building’ as the object of assessment

Downsides: eTool’s automated report will say ‘NLA’ instead of ‘GFA’. This may not be an issue if you are submitting your own customised reports.

Method 3 – Zero Carpark GFA

1. Set the carpark function as the Supporting Function 
2. Zero out the GFA for the carpark function
3. Generate report with ‘Whole Building’ as the object of assessment

Downsides: Need to check and update any inputs/templates in the design that reference the ‘GFA’ expression from the carpark function.

 

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