Dear all,
I have a question regarding the garage ventilation. Suppose I have the enclosed garage, for example the garage below the ground. Under this condition, the ventilation for the garage area only depends on the mechanical ventilation. The enclosed garage is not conditioned.
From the scenario described above, can I assume that the garage ventilation belongs to the process load? This means that the baseline garage ventilation should be simulated identical to the proposed model. For example, the baseline garage ventilation will have the same DCV control schedule and the same VFD motor control as the proposed model and the proposed garage ventilation fan cannot claim saving.
Thank you
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
October 20, 2020 - 2:23 pm
Yes, parking garage ventilation is still a process load and the inputs are still included in the Process Loads section of the v4.1 Minimum Energy Performance Calculator. However, you may still be able to claim savings using the approach from LEED Interpretation 10371. Although this interpretation has not been applied to v4.1, the referenced Section 6.4.3.4.5 has not changed between the 2010 and 2016 versions of ASHRAE 90.1.
Ying Lindsey
6 thumbs up
October 23, 2020 - 4:40 am
Thank you for the response Tyler, I still have some questions regarding this issue.
1) If the local code requests the DCV control for the parking garage, can the project still claim credit from DCV control? I found a similar discussion here LINK https://leeduser.buildinggreen.com/forum/taking-credit-dcv-car-parks. This clarified that if the law requests the DCV control, no credit can be claimed from the parking DCV ventilation.
2) I checked through LEED Interpretation 10371, and it clarified that the baseline garage fan should be simulated at 0.3 watts per CFM. And the CFM is determined by 0.75 cfm/sf. It seems the baseline garage fan needs to be stimulated as a constant air volume fan. However, if the baseline garage fan is simulated as a constant air volume fan, how should the DCV control be realized? Since the purpose of DCV control is to reduce the ventilation when it is not needed, the garage fan ventilation system is 100% OA system. Under this condition, the ventilation will not react to DCV control. Please correct me if I understand the DCV control incorrectly.
Ying Lindsey
6 thumbs up
October 23, 2020 - 5:23 pm
https://leeduser.buildinggreen.com/forum/ventilation-process-load
In that discussion, Marcus mentioned that the LEED clarified process load is not a regulated load. Does that mean Garage Ventilation Fan belongs to an un-regulated load that will not be affected by the building performance factor?
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
November 5, 2020 - 3:34 pm
1) LEED Interpretation 10371 seems to be applicable whether or not DCV control is requred by the local code, so I would still think you could claim credit.
2) I believe this question no longer would apply since you don't need to model DCV control in the Baseline.
Garage ventilation fans are "process" in the sense that their modeling is not defined by Appendix G and therefore should be modeled identically by default, with any savings modeled using an exceptional calculation (or applicable LEED Interpretation such as 10371). I am unclear on your question about the building performance factor.