ID#10277 made on
EAc1 - Optimize energy performance
LEED BD+C: New Construction, LEED BD+C: Schools, LEED BD+C: Retail, LEED BD+C: Healthcare
The purpose of this inquiry is to determine if our approach for energy modeling required by credits EAc1 and EAc5 is acceptable. Our project is a 215,800 square foot patient room and administration of...
The purpose of this inquiry is to determine if our approach for energy modeling required by credits EAc1 and EAc5 is acceptable. Our project is a 215,800 square foot patient room and administration office addition to an existing hospital. The LEED boundary for the LEED certification includes the new addition only. A boiler and chiller plant provides heating and cooling to the existing hospital and is located within the existing building. The boiler and chiller plant equipment will be demolished and a new, larger boiler and chiller plant will be built within the new attached addition, and will serve both the new addition and existing hospital. The new building addition within the LEED boundary will be served by its own air handling units with hot- and chilled- water coils served from the new mechanical plant which is also within the LEED boundary. We would like to confirm that the following approaches are acceptable: 1) Exclude the existing building which is outside of the LEED boundary from the energy models; and 2) Model the new addition in the budget and proposed design models with a mechanical plant that is appropriately sized for the addition only, and use in the models the efficiencies of the plant equipment that is sized to serve the entire hospital. The equipment sized for the new addition only is in the same size category referenced in ASHRAE 90.1 Section 6 as equipment sized to serve the entire building, so the efficiencies would be the same.
"The proposed modeling approach of sizing the plants within the model for the new addition only is not acceptable. However, since the new mechanical plant located within the LEED Project Boundary is intended to serve both the LEED project building and the remaining existing portion of the building, the plant would effectively be a district thermal energy plant. Therefore, the project team is encouraged to utilize the Treatment of District or Campus Thermal Energy in LEED v2 and LEED 2009 Design & Construction (DESv2.0).
Per the DES guidance, the proposed building heating and cooling are to be modeled using a virtual plant, with average efficiencies that are determined using either the monitoring or modeling methods described in Appendix C. Note that the DES Guidance indicates that when the building housing the thermal energy plant is itself seeking LEED certification, then the project shall treat the DES equipment as downstream equipment for certain prerequisites and credits (including commissioning credits: EAp1 & EAc3, refrigerant credits: EAp3 & EAc4, and measurement and verification: EAc5). However, for the energy model, the district energy equipment shall be modeled as upstream equipment, and the project is recommended to use modeling Option 2, which is allowed even if the minimum point floor from Table 1 is not reached for the project. Although the existing portion of the building does not have to be modeled explicitly, some form of modeling of the district plant and the total load from all buildings (or portions of the building) anticipated to be connected to that plant is required in order to calculate the average efficiency. Generally, some form of load calculation, and identification of predicted load profiles is used when sizing a central plant, and identifying the central plant equipment that will be installed. This data can be used to develop a simple central plant energy model, where the loads from all of the buildings are modeled using the combination of a process load on the plant and a schedule. As stated in Appendix C, average efficiencies may be determined annually, seasonally, monthly, hourly, or for each utility block, as long as the same time scale and method used (either monitoring or modeling) to derive the average efficiency for heating or cooling is consistent for all related district thermal systems that are part of the LEED project. Please note that this means the schedules modeled for this plant model may be as complex as hourly schedules with predicted variations for each hour of the year, or as simple as an annual average load on the district plant assumed for the whole time the plant is anticipated to be operating on an annual basis. For EA Credit 5: Measurement and Verification, clarification should be provided to identify how the energy loads (including thermal loads) for the new addition will be metered separately from the energy loads for the existing building.
Note: This interpretation ruling does not address whether the building addition qualifies with the (Guidance for Certifying Attached Buildings Separately) which is also contained in Version 2 of the LEED 2009 MPR Supplemental Guidance Document.”
Related Addenda (Corrections & Interpretations)