James,

My understanding is that the baseline model becomes a bit of a mix for existing buildings (and no, 90.1 2007 doesn't clarify much). The basic rule I've followed is this: any part of the building that will be touched by the new design should be modeled in the baseline per ASHRAE 90.1. In other words, there's an implicit assumption that the existing building is below the current ASHRAE minimum, and the minimum improvement for the proposed design would be to bring it up to the standard. LEED credit is earned only by exceeding this minimum improvement.

I would therefore answer your two questions as follows:

1) Are the HVAC, thermal parameters, and lighting being touched by the proposed design? If so, then model them in the baseline per 90.1. If not, then baseline = proposed = existing conditions.

The problem with the methodology above arises when existing conditions currently exceed ASHRAE minimums. If this is the case, I would either review the LEED CIR archives for advice, or I would model the existing condition in the baseline and include a narrative with the submission explaining that the existing condition already exceeded the ASHRAE minimum. I admit I have not encountered this before, but I believe EA Credit 1's intent is best served by maximizing the baseline performance.

2) Model the baseline with windows on that facade, percent matching the proposed design if it's under 40%, but obviously keep the baseline window performance as specified in 90.1.

I would appreciate anyone with differing advice to sound off; I'm working on similar projects that would be affected, and I've had to change my interpretation in the past. Thanks,

Dakota