Is anyone aware of how/whether LCA’s typically include the area of elements like balconies, a large uncovered deck, or parking in a project’s gross floor area for assessing whole-building GWP impacts?
We are doing LCAs that include parking structures, balconies, partial interiors (e.g. warm shell), etc., but this definition of Gross Floor Area from USGBC seems to exclude uncovered exterior space, so I’m not sure whether GFA typically includes these.
The best option I can think of is to provide separate areas for each portion of the building so that we can understand EC intensity by portion (e.g. enclosure, area with interior finishes, and maybe conditioned and unconditioned area). Then we could use the whole “usable area” (conditioned and unconditioned) for an overall EC intensity - with ability to filter by what all contributed to that intensity.
Great question - I’m curious if we can lean on IBC definitions for building area? It would be great for us to help harmonize with established code language!
Hello CLF Community. This question is coming up again as we get further into benchmarking. @bbenke do you have a take on the above? @louise.hamot are you aware of anything from RICS related to inclusion of large uncovered exterior spaces?
One of my colleagues has suggested “the NRC guide to WBLCA which recommends using the CIQS guidelines to measure GFA, and the method is included (starting page 97).” She also cited this study, which shows that varying approaches to GFA calculation can significantly influence a project’s GWP intensity.
I’m curious to hear what others are doing or if there’s a standard to follow.
Yet another topic that needs standardization, especially in North America. Yes - it can result in big differences for EC intensity. It’s another reason why having more metrics beyond total kgco2/m2 can be really useful.
Ultimately it all depends on what LCA requirement or purpose of assessment you’re pursuing. They will likely have different definitions. My opinion is that whether it’s part of the GFA or not it’s still carbon emitted, so we need to work towards a system that captures as much scope as possible and reports it in clear and useful ways. But we’re not there yet… We’ll be getting into this a bit for the CLF benchmarking study.
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!
Finally getting around to reading the SBTI document on building-related emissions. They reference this standard for defining the floor area used for normalizing emissions to a per-area basis:
Thank you for the detailed responses here. Its clear that we have a long way to go in terms of alignment (starting from how to measure the area requirements of one project, all the way through metrics for normalization).Since different standards are approaching this differently - we are capturing the impacts we’re able to, and as long as we have the data and project metrics, these can be assessed in a variety of ways until there’s more alignment. I do still feel that normalization is important for numerous reasons, yet agree that this should not be confused with a building as a functional unit.
Another, somewhat related question. Some have recommended normalizing projects based on # of occupants they are designed for. Do you (or do others) have resources for how to assess # of occupants? Is this more related to energy and water use - and thus should align w/ the Energy Model?
Replying to my own question about occupancy. CLF’s metrics are defining “occupant load” as
“the total number of occupants for whom egress facilities are provided.” So this is one approach.
