Background The Phoenix Sky Harbor International Airport Automated Train project consists of an automated electric train which travels on an open, elevated railway serving three train stations. One station is attached to the existing air terminal building #4, one makes connection to the municipal light rail station adjacent to the airport at 44th Street, and the third (the EEL Station) is located on the rail system part way between these stations and adjacent to an existing parking garage. The terminal #4 and 44th St. stations are enclosed and conditioned and the application of LEED criteria is fairly straightforward. It has been suggested by value engineering that the EEL station be constructed as an "open" or unenclosed, unconditioned structure with a roof and interior lighting, but no exterior walls. The station will include normally unoccupied, enclosed, and conditioned ancillary equipment rooms which house electrical and communications/security equipment. It is anticipated that these ancillary areas will constitute about 5% of the total building area. Credit Interpretation Request This question deals with how the unconditioned, unenclosed portions of this building can evidence compliance with EA prerequisites and credits. In researching past CIRs on the USGBC website several cases involving unconditioned buildings were found, but none matched our project sufficiently to provide a level of confidence in the interpretation of requirements. In the proposed design, the unconditioned, unenclosed portions of the building will be naturally ventilated with no HVAC equipment, while the enclosed ancillary equipment spaces will be conditioned with conventional A/C or evaporative cooling and electric heating equipment. It is desired that the entire building be considered for certification, not just the ancillary areas. In configuration, this building most resembles a parking garage where there is lighting, vertical transportation, and conditioned ancillary areas, but no conditioning or enclosure of the occupied areas. The LEED NC Version 2.2 Reference Guide (First Edition) indicates on page 181 under HVAC system types that "For areas of the project without heating or cooling systems (such as parking garages), there is no need to model heating or cooling systems in either the Proposed or Baseline designs. This was supported by the CIR ruling dated 1/29/2008 relating to a CIR submitted on 1/11/2008 that addressed energy use simulation of unconditioned buildings. The Ruling stated "For EAc1, these buildings would be treated very similarly to unconditioned parking garages, where the envelope does not necessarily need to be modeled, but the electric loads from the lighting and fans are included in the energy calculations." Will it be permitted to treat the EEL station in this fashion, where the energy simulation will include use by lighting, vertical transportation and other ancillary energy uses, but not HVAC systems in the unenclosed areas? The HVAC systems serving conditioned equipment rooms will be included in the simulation and their performance will be compared with the baseline systems specified by ASHRAE Std 90.1 - 2004, Appendix G. Since the envelope requirements of ASHRAE 90.1 - 2004 do not apply to unenclosed and unconditioned buildings, may we assume that EAp2 is automatically satisfied for the unconditioned portions of the buildings and only the conditioned, ancillary portions of the building must comply?