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NC-v4 MRc1:Building life-cycle impact reduction

Operational Energy

When conducting a LCA will the baseline and proposed building have the baseline and proposed energy usage accordingly (as per Minimum Energy Performance calculations) or will both have the same energy usage?

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Paula Melton
Editorial Director
BuildingGreen, Inc.
LEEDuser Expert
159 thumbs up

Thu, 12/04/2014 - 16:00

Charalampos, yes, the reference guide states that energy use must be the same in the baseline and design cases (otherwise you would get to double-count for optimizing energy performance). Other parameters that must remain the same: 1. location 2. function 3. gross floor area 4. orientation 5. 60-year service life

Thu, 12/04/2014 - 16:13

Thank you Paula. However, from a previous reply from GBCI we got a response that the intent for the MR Credit: Building life-cycled impact reduction is to encourage adaptive reuse and optimize the environmental performance of products and materials. The energy consumption of the project should be irrelevant. To this, the LCA models (baseline and proposed) must meet EA prerequisite Minimum Energy Performance by adhering to the requirements of ASHRAE 90.1-2010, Appendix G, Opaque Assemblies, Vertical Fenestration, Skylights, and Roof Solar Reflectance and Thermal Emittance sections. This is sensible though, since in a different case the reduction in the global warming potential would not be tangible (when comparison between baseline energy and proposed energy is not allowed for the needs of LCA). Additionally, it is stated that energy modelling is not required for LCA. In general, I reckon that the Reference Guide is not that clear to that point.
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Paula Melton
Editorial Director
BuildingGreen, Inc.
LEEDuser Expert
159 thumbs up

Thu, 12/04/2014 - 16:20

I'm not sure I fully understand your comment, but to put it more simply, the intent of the credit is more related to embodied environmental impacts rather than life-cycle impacts the products have on the energy performance of the building. There would certainly be tradeoffs here. For example, for Optimize Energy Performance, you may have an incentive to use huge amounts of foam insulation. For Whole-building LCA, there would be a major disincentive to use foam insulation with high global warming potential. That both baseline and design cases have to meet certain prescriptive requirements of 90.1 only suggests to me that they have to be on a level playing field in terms of operational energy, so it's an expansion of that requirement.

Thu, 12/04/2014 - 16:26

I totally agree with your comment. However, practically, the outputs of the energy modelling process (annual energy conumption in kWh) will not be inputs for the LCA models, will they?
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Paula Melton
Editorial Director
BuildingGreen, Inc.
LEEDuser Expert
159 thumbs up

Thu, 12/04/2014 - 16:36

It probably depends which software tool you use, but energy consumption is simply moot for this credit. Process-wise, I'm thinking you would probably need to do the WBLCA long before the final energy model anyway; the final energy model needs the final material inputs. In short, this is about materials and their embodied impacts, not their impact on overall energy performance.

Thu, 12/04/2014 - 16:43

Paula thank you so much for your clear response. Obviously, energy use is not part of the scope of LCA, whereas compliance to Appendix G of ASHRAE 90.10-2010 is. However, the term “operational energy usage” referenced in the Reference Guide (p. 502) is a little bit misleading.
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Paula Melton
Editorial Director
BuildingGreen, Inc.
LEEDuser Expert
159 thumbs up

Thu, 12/04/2014 - 16:48

Yes, I see what you mean; it makes it sound as though you will need to do the energy model as an input for the LCA. I think in reality they're just trying to make sure people don't try to game the system by reducing operational energy use when documenting this credit. It could also be accidental because people might think, "Well, if I switch to polyiso from mineral wool, I have lower embodied energy as well as lower operational energy." That may or may not be the case (I don't actually know how embodied energy compares between those two!), but you can see how people might make that mistake and try to include it in the LCA calculation. I think they're just trying to be really clear that these are totally separate calculations and you can't use improved energy performance to offset material impacts.

Thu, 12/04/2014 - 16:54

That is true. But in order to make it crystal clear they should simply state that energy use is not part of the LCA, since it covered by another credit/prerequisite (EAp2) and hence, project teams must not include energy use in the LCA models, instead of stating that “...The proposed and baseline buildings ….. must have the same ….. operational energy usage...” (p.502) because this means that energy use calculated from energy modelling is required for input. Once again, thank you very much for your assistance.
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Panu Pasanen
CEO
Bionova / One Click LCA
LEEDuser Basic Member
19 thumbs up

Fri, 06/10/2016 - 10:40

Charalampos, you're right, it should be spelled out more clearly. But the list of things to be included in the "scope of assessment" does not include energy. From my discussion with people who'd been drafting the credit the idea of stating the energy consumption must be the same was to prevent (fictive) dematerialization by reducing insulation compared to baseline. So Paula's comment on "level playing field in terms of operational energy" is spot on.

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