Hi all,
We are working on an existing small project (35,000 SF approx) that is going through a major renovation, where most of its systems are being updated, including new AHUs, however, the project will keep the existing air cooled chiller. Two scenarios come to mind on how to properly assess the project's performance:
- Model a Baseline vs Proposed as a regular new construction: baseline type 6, with no changes, and proposed as designed (including old chiller).
- Model a Baseline vs Proposed but both with the old chiller: the baseline would be type 6, but for the cooling, instead of direct expansion the coil will be connected to the same, existing, chiller (just as the proposed).
Any thoughts?
Thank you,
Tyler Thumma
7GroupLEEDuser Expert
62 thumbs up
May 7, 2024 - 8:34 am
In the scenario you describe I would recommend option 1, which is always an acceptable approach.
Existing HVAC systems should only be modeled in the Baseline for spaces where the existing HVAC systems are entirely separate from the modified or new systems serving the remainder of the building, AND are not modified as part of the scope of work. If using this approach, it must be used consistently for all applicable spaces. Repairs/retrofits are not considered “modifications” or “alterations”. Replacement of an HVAC system (or portion thereof) would be considered a modification (or alteration) to the system, in which case the corresponding ASHRAE baseline would need to reference the ASHRAE 90.1 Section G3.1 requirements as if the HVAC system were new. If chillers, boilers, heat rejection equipment, and/or air handling units are replaced, and downstream fan coils or VAV boxes are not replaced, the Baseline should be modeled consistent with ASHRAE 90.1 Section G3.1 Baseline HVAC system types and requirements.