The Yale Social Sciences Building will be a 72,000 ft2 addition to the Yale University campus in New Haven, Connecticut. The design is currently in the CD phase, and the building includes classrooms, study areas, and faculty offices. Like the rest of Yale University\'s central campus, this building will be connected to the Yale Central Plant for supply of chilled water, steam, and electricity. The Yale Central Plant is a highly efficient generator of steam, chilled water, and electricity. By making use of natural gas to generate steam in high efficiency boilers, the plant can then choose to produce variable amounts of electricity and chilled water from steam driven turbines and chillers, in addition to natural gas turbines. Though the plant itself is highly efficient, the pricing of its product is inclusive of an extensive supply network and union labor force. The central plant is up-to-date with LEED compliant refrigerants, NOx, SOx & particulate filtration, and is part of the Yale initiative to reduce campus greenhouse gas emissions 10% below 1990 levels by 2020. In comparison to the extensive use of trash-to-energy in CT, we feel that this is an efficient source of local clean energy for the building. This credit interpretation request is in regards to energy modeling of the chilled water sourced from the Central Plant for cooling as compared to the baseline building. Intended to discourage the use of old, inefficient central chilled-water plants, ASHRAE 90.1-2004, Appendix G requires that the Baseline Building be simulated with a DX rooftop system. The annual energy costs for the Baseline Building are then compared to the annual energy costs of the Proposed Building, which uses chilled water from a central campus plant, to determine the number of credits attainable under EAc1.1-1.10. This comparison is problematic, because it penalizes any building without on-site chilled water generation, regardless of the efficiency of the central plant. An energy consumption comparison between the Baseline Building and the Proposed Building will then be inaccurate, because chilled water demand does not incorporate any coefficients of performance (COPs) for the chilled water generation. Therefore, following the ASHRAE methodology, it will be difficult to meet the Minimum Energy Performance prerequisite of LEED-NC 2.2, much less earn any EA-1 points. Exacerbating the problem, the highly-efficient central plant reuses energy at every step of the production process, making it difficult to price each utility completely accurately. Thus, the ASHRAE 90.1-2004, Appendix G model is not a comparison of the Baseline and Proposed Building\'s energy efficiency, but instead is a model of the discrepancies between the prices of electricity and chilled water. One method of creating a useful comparison between the Baseline and Proposed Buildings would be to "normalize" the cost of electricity relative to chilled water. As the USGBC has previously established that utility costs must be inclusive of all labor and delivery costs and cannot be modified (9/19/2006), we propose the following alternate method for modeling the Baseline Building. We propose that in the case of a new building being serviced by an existing campus utility plant, the ASHRAE 90.1-2004 Baseline Building use chilled water from the central plant. Utilized under previous versions of ASHRAE 90.1 and currently under ASHRAE 90.1 - 2004 for all but the method stipulated in Appendix G, the proposed methodology provides a more accurate depiction of energy savings achieved in the Proposed Building. It would provide a consistent comparison of cost of energy to the owner and more realistically equate energy savings with LEED points. Please confirm that the USGBC will find it acceptable to use this methodology when dealing with new buildings on the Yale campus that connect to the campus central plant.