This is a supplementary post that explains in further detail how Primary & Supporting Functions work.
The main purpose of the Functions feature in eTool is to 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.
Generating LCA Report with ‘Primary Function’ as Focus
When you have one Primary & one Supporting function, be aware that when you generate the LCA report with the Primary Function as the object of assessment, the report will include the impacts of ALL inputs that have been assigned to the Supporting function as well. The main difference with how the report is generated however, is that when you specify a functional unit such as m2GFA, the results will calculate the GWP impacts based on the floor area as per the parameters specified in the Primary function only.
Example: Total GWP for the building is 1000kgCO2e. Floor area for the Primary function is 100m2 but for the Supporting function, it’s 50m2. When you generate the LCA report with the ‘Primary Function’ as the object of assessment & a functional unit of m2GFA, the total GWP results in the report will be 10kgCO2e per m2 of GFA (Primary floor area only).
Generating LCA Report with ‘Whole Building’ as Focus
If you’re generating the report with the functional focus (Object of Assessment) set to ‘Whole Building’, be aware that if you set the Functional Unit to ‘m3GFA’ the software will use the combined figure of all the functions’ GFA (including all supporting functions).
Example: Total GWP for the building is 1000kgCO2e. Floor area for the Primary function is 100m2 but for the Supporting function, it’s 50m2. When you generate the LCA report with the ‘Whole Building‘ as the object of assessment & a functional unit of m2GFA, the total GWP results in the report will be 6.667kgCO2e per m2 of GFA (Primary + Supporting Function gross floor area).