Really appreciate this conversation and want to put another vote in for thinking about total emissions and not necessarily emissions intensity. Going to put on my “letter of the law” hat both because I think it’s clarifying and that it’s also the best way to measure real impacts. In advance, please pardon my punctiliousness.
I want to comment here to untangle two important issues: the LCA’s functional unit and the normalization of LCA results. In my opinion, floor area is inappropriate as a functional unit but reasonable as a reference value for post facto normalization.
LCA is performed on the basis of a functional unit and in wbLCA the functional unit is typically the entire building. Quoting EN 15978 (7.2), the “functional equivalent” must include:
- building type
- revelant technical and functional requirements (e.g. regulatory and client’s specific requirements)
- Pattern of occupancy
- Required service life
To meet this requirement, LCA can’t take “one meter square of GFA” as the functional unit with which to conduct an LCA. So the LCA itself needs to be performed to cover a broadly defined functional basis, not a narrowly defined GFA requirement.
Once the LCA is done, it can be convenient to put the results of various analyses on a common basis for comparison. This is the normalization step (indicated as optional in ISO 14044), which might include calculating an Embodied Carbon Intensity by dividing by total GFA. Normalization is only meaningful as a way to present results based on equivalent functional units, not as the functional basis for the analysis itself.
See further Note 2 in EN-15978-7.2 and ISO-104044-4.4.3.2.
Happy to discuss further, but thought these references might be helpful!