Welcome to the Discussion about the Beginner’s Guide to MEP Embodied Carbon, a comprehensive resource developed through cross-industry collaboration between MEP 2040 and the Carbon Leadership Forum.
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After reading through the guide I noticed a couple of things that were not listed. Firstly was GRD’s (Grilles Registers and Diffusers) I assume that these must be accounted for and there could possibly be a significant amount of embodied carbon not accounted for. Secondly I did not see any mention of control or data cabling, there is the potential for miles of cable not accounted for. Just some food for thought in the future updates. Would be curious to know if anyone accounts for these things now??
@mreese thanks for the feedback on the Guide. The reason for the exclusion of both the GRD devices and data/comms infrastructure is that this initial version of the Guide is written with a focus on Level 300 model documentation (so that design teams have some runway to make decisions before the project gets completed). As such, we rarely see placement of diffusers or registers, or any data/comm cabling at DD/Level 300.
As we get more constructed projects, with accurate bills of material, we could use the same methodology to account for the embodied emissions of these systems/items, and with enough data points, perhaps develop a proxy to estimate their impact during earlier stages of the design process.
We are trying to home in on the 20% of “stuff” that accounts for 80% of the up-front emissions (see: Pareto Priinciple). While GRD and data/comm systems may account for a significant amount of A1-A3 (and perhaps, a fair amount of B4), we also need to consider what steps we might take to reduce that impact - are there lower emission material or system alternates?
@mreese One can look to manufacturers who have already developed EPDs for grilles, registers and diffusers. I suggest visiting Environmental Product Declarations | www.swegon.com for GRD EPDs.
B2-B3 exception for high efficiency filtration
In going through another case study, where the air handling systems used high efficiency filtration (i.e. MERV 14 12"-thick filters), we noted that the life-time B2-B3 Maintenance and Repair is much higher than 3% of the AHU A1-A3 embodied carbon. During the 25-year service life of an AHU with A1-A3 embodied carbon of 30 mTCO2e, the embodied carbon associated with the replacement and disposal of the MERV 14 final filters serving that unit would be about 13 mTCO2e, well in excess of the 3% allowance (page 46, Table 16) recommended in the Beginner’s Guide to MEP Embodied Carbon.
We recommend, if your project uses higher than MERV 8 filtration, that you take the time to estimate the embodied carbon associated with the replacement and disposal of high efficiency filters and add that to the 3% allowance identified in the Guide.
B7: Operational Water Use
In going through the latest draft of ASHRAE Standard 240P Quantification of Life Cycle Greenhouse Gas Emissions of Buildings for Operational Water Use (section 7.4), I noted that, consistent with what was published in the 1st draft, so no longer open for public comment, the energy-use factors are considerably different than what we have on page 51 of the Beginner’s Guide (0.35 kWh/m3 of water use). I assume that, in the next edition, we will update those emission factors, and include the impact of wastewater energy-related use, as well.
For what it is worth, these are the Standard 240P factors: 0.75 kWh/m3 of electricity for municipal water; and 0.56 kWh/m3 of electricity plus 0.23 kWh/m3 for natural gas for municipal wastewater.
I wasn’t involved in the B7 energy defaults for either 240P or MEP 2040. So I can’t comment on where 240P’s came from, but they have been the same since the first draft in April 2023. Looks like MEP 2040’s came from an IEA report. Is there reason to believe 240P’s is more credible? EPA still has a bunch of (dated) reports listed ( Energy Efficiency for Water Utilities | US EPA ) including this 2012 World Bank report which more closely matches the MEP 2040 guide. https://www.esmap.org/sites/default/files/esmap-files/FINAL_EECI-WWU_TR001-12_Resized.pdf