We are designing an addition to a solid waste transfer station facility for the South Bayside Waste Management Authority in San Carlos, CA. The floor area of the addition will be about 22,000 SF, and the overall building area including the addition will be about 75,000 SF. After the addition has been completed, there will be no wall or physical barrier between the addition and the original structure of the building, although both the new and the existing component will be served by independent HVAC systems, lighting controls, etc. Several floor openings to a tunnel below will prevent traffic between the addition and the existing portion of the building, but the two structures will basically be open to each other. May we certify only the addition to the transfer station, or must the existing building be certified as well? If the addition may be certified as a single structure, we propose that the interface between the addition and the existing building be modeled as a partition with no R-value. Is this acceptable?
The project team is seeking guidance on LEED certification for an addition to an existing solid waste transfer facility. The project team is also asking for modeling guidance for representing relationship of the addition to the existing facility. The addition may be certified separately and modeled where the performance excludes the existing building if it meets the conditions laid out in ASHRAE 90.1-2004 Table G3.1 Section 2: Additions and Alterations. Given the information presented, the project seems to meet these requirements; however, compliance cannot be assessed outside of the certification process. In modeling the addition and excluding the existing building, the open interface between the addition and the existing structure should be modeled as an adiabatic wall. If the existing building may not be excluded per ASHRAE 90.1-2004 Table G3.1 Section 2; modeling the partition between the existing and new components with no R-value (i.e., as an air wall) is acceptable