The following Administrative CIR is posted by USGCBC to provide additional guidance on projects that include an existing building, regarding the energy model\'s requirements for baseline building envelope.
The following section from ASHRAE 90.1-1999 states that the budget building envelope for existing buildings is the building prior to any modifications. This section applies only to the building envelope for existing buildings. Section 11.4.2 Building Envelope. The budget building design shall have identical conditioned floor area and identical exterior dimensions and orientations as the proposed design, except as noted in (a), (b), and (c) in this clause. For existing building envelopes, the budget building design shall reflect existing prior to any revisions that are part of this permit. Applicable internationally.