Hello all,
On a recent LEEDv4 project we were pursuing the WBLCA credit. It was an office tower. Our baseline was an older design concept with concrete structure and precast cladding, and our proposed design was a steel structure with mostly curtain wall.
We were using Tally, and with the proposed design we could show that we made massive reductions in all impact categories except for ozone depletion potential - which basically doubled in the proposed steel structure. So even though we were reducing GWP by over 30% the LEED requirement to "not reduce any one category by more than 5%" was preventing us from getting the points (we later made other design changes to still get the points). Seeing that ODP is significantly less important than GWP it seemed like a shame that LEED was set up that way.
I did some digging on this topic and found that the data Tally was using for steel was slightly out-dated, and that there was more recent data from Worldsteel that would not have shown such big impacts for ODP.
I would love to here the communities thoughts on these two topics:
- Has anyone ever put in a credit interpretation request to argue that GWP impacts far outweigh ODP, or any impact category compared to another depending on the severity and geographic project location? I'm wondering if there is a case to be made that in some instances the credit requirements don't make a lot of sense. One idea that we heard about was adjusting the data with normalization factors based of the NIST metrics.
- Addressing data uncertainty - The credit language states that the same LCA software/tool/data must be used for both the baseline and proposed buildings. But it doesn't necessarily say that all data must be contained in the same tool. Would it be acceptable to swap out data from the tool, as long as you swap it out for both design options and that it is ISO 14044 compliant? In our case this would mean manually inputting updated WorldSteel data for both designs while using the generic Tally data for everything else.
Looking forward to hearing your thoughts.
Jennifer O'Connor
PresidentAthena Sustainable Materials Institute
6 thumbs up
April 3, 2018 - 12:48 am
Brad, thanks for sharing this example of why both the ODP and the 5% need to go in this credit. We will be putting in our two cents with USGBC suggesting that change for v4.1.
ODP numbers are always very, very small - you could increase your ODP result by 100% and it still wouldn't be a big deal (not that it matters for the on-line form for this credit, which, last time I checked, doesn't have enough significant figures past the decimal to accommodate the ODP range of numbers, so everything zeros out anyway). In the LCA world, ODP is seen as relatively unimportant. Of all the categories, this is the last one that ought to have the power to torpedo an otherwise great project.
Meanwhile, the 5% limit is well-intentioned but misguided. Not only is 5% within the margin of error in LCA, but what a shame to see projects that do really well in five out of six categories not get the points. The credit is missing out on the value of LCA in examining (and accepting) trade-offs.
Regarding your data swap question, in our opinion, if you know what you're doing (and it sounds like you do), then it should be just fine.
Calie Gihl
Design EngineerLEEDuser Expert
19 thumbs up
April 16, 2018 - 6:59 pm
Hi Brad,
I also work on WBLCA's using Tally! My colleague and I discussed your question. I think the biggest concern we could think of with regards to swapping data would be to check that your metadata is in alignment - for example, is it the same system boundary, same functional units, etc.
And not to get too philosophical, but I don't know if you could quantitatively weigh one environmental quality as being more impactful then another - we all live on this planet, after all! To me, it seems like this credit requires more of a discussion/qualitative result in addition to the LCA software results. The results of this credit deserve a higher level of consideration, in my opinion, than other credits which are more "plug and chug."
Brad Benke
ArchitectMcLennan Design
2 thumbs up
April 25, 2018 - 12:32 pm
Thanks Jennifer and Calie. Some great thoughts.
I agree that weighing one impact against another can be a potentially slippery slope but I do think this needs to be addressed in some fashion. As Jennifer mentioned, 5% can easily pop up just in rounding data for something that small. I think a lot of people that are doing LCA for LEED are seeing issues with the credit language in this regard.
Jennifer - I'd be curious to know what type of language you are suggesting for the 4.1 updates.
Thanks,
Jennifer O'Connor
PresidentAthena Sustainable Materials Institute
6 thumbs up
April 26, 2018 - 7:15 pm
Brad, we'd like to see:
Removal of the proviso that no measure can exceed the baseline by 5%. Either remove the entire condition that one exceedance kills the credit, or just remove the 5% (i.e., allow any amount of exceedance in one credit).
Removal of ozone depletion potential, especially if the 5% stays.
An option for partial credit just for doing LCA, without comparison to a baseline.
An option for extra credit if a project submits a bill of materials to help us create a buildings database and a benchmark system that will simplify and standardize the "reference building" approach.
And a few technical fixes to the reference guide.
Dionisio Franca
DirectorWoonerf Inc.
30 thumbs up
April 26, 2018 - 8:55 pm
Hi all,
I'd like to add something I think should be changed on the credit requirements. I think the baseline should not be mandated to be similar to ASHRAE 90.1 requirements. In the market I work in, Japan, this would artificially make all projects start in a very easy position, because we don't insulate our buildings as well as ASHRAE requires.
Panu Pasanen
CEOBionova / One Click LCA
25 thumbs up
April 27, 2018 - 1:28 am
Hi Dionisio,
as per the reference guide the ASHRAE provisions do not apply to projects outside United States.
BR Panu