Option 2: Insulation for Baseline and Proposed

In general with an existing building you model the baseline with the existing conditions and the proposed as designed. If you added insulation you can take credit for it. For this particular credit under Option 2 you can only count any savings from HVAC systems and equipment so I have always assumed the other parameters like lighting envelop, etc. must be identical so that there is no savings generated from these strategies. Maybe I am missing something?

Victor & Catalina, The "Tips" may have just mis-worded the sentence to which you are referring. In fact, as I read through the Tips, I don't quite see where it says to use the existing wall in the proposed case model. Option 2: Performance Path: ASHRAE 90.1, Appendix G, Envelope; 2nd & 3rd notes read; "Be sure that the proposed case U-values are consistent with the various wall and roof construction assemblies listed in Appendix A of ASHRAE 90.1." "Don't forget to model the baseline case exterior wall, roof, floor/slab constructions and reflective roof as required by ASHRAE 90.1 Table G3.1-5 and Table 5.5" Neither of these Tables appear to say you cannot take credit for your design to add insulation. Please let us know what section of the "Tips" you are reading, I seem to be overlooking it. I feel like this is one that would be worth attempting the way Marcus described, for the first LEED submission, at least. I believe Marcus is correct in his assertion of the LEED credit's "intent", but submitting under these circumstances (first submission to GBCI) gives you the opportunity to get direct/specific feedback from the LEED reviewer about your project, and the opportunity to make revisions. It seems as though you believe that the "spirit" of LEED would want you to take credit for your effort to insulate the walls, and Marcus agrees with this inclination. I think if I were in your situation, I would just explain the rationale to the reviewer in a narrative. Site the sections of 90.1 that allow modeling of the existing condition as baseline case, and utilizing the designed envelope as proposed case.

Agreed. The way I interpret those statements: Proposed: Confirm that your Proposed Case (after renovation) wall construction overall U-value is calculated using the U/R-values provided in Appendix A for each "layer" of material making up the assembly. And, always remember to account for insulation between studs, if applicable, to match the R-value of that layer in your wall assemblies, per Appendix A. Baseline: Per the note in Table G3.1-5f, model the Baseline Case envelope as the existing (pre-construction) assemblies. Again, match the U-values for each layer with Appendix A. Again, however you interpret the codes, include your justification in the narrative. This way you can state why you proceeded as you did, and a reviewer will either understand/agree with your choices, or let you know what they feel you should revise. In the end, it seems, it's always up to the Authority Having Jurisdiction. All you can do is present the most logical rationale available to back up your assumptions, and hope they agree. In this case, both Marcus and I feel you should be able to take credit for your effort to insulate the walls.