[Bldg-sim] Garage Ventilation and LEED Credit EA-1

[Fred Porter]

All,
While I'm still on my first cup of coffee, and considering the PRM, general "baseline/budget/reference" model philosophy, and others' views on safe ventilation, another answer would be the default "baseline" = "proposed" operation and equipment, where the PRM does not specifically state a baseline. (You could still take credit for a premium efficiency fan motor.)
 
I certainly suspect that savings have been granted to parking garage "DCV" by lenient reviewers, but it has not surfaced in a CIR.  Of course, clients might think it tacky of us to ask for stricter limitations and reduced savings and points in a CIR they pay for, which is a problem with the process. The fact that the baseline is unclear to experienced EA Cr1/PRM modelers says a lot, since there must be a couple million sf of ventilated parking garages rated or in the pipeline.
 
Oh yeah, and what about those heated parking garages under every "green" office and resort hotel? 
 
And as far as "substituting" the cooling tower fan during summer; I would think drawing air through the garage with the CT fan would add some constant load to, or reduce the flow through, that fan, partially offsetting savings from turning off the garage fan (which would have operated at a low load factor if controlled by the typical sensor). 
 
Off to work;
Fred


>>> "Fred Porter" <FPorter at archenergy.com> 2/12/2008 2:27 PM >>>
>>> "Michael Tillou" <michael.tillou at gmail.com> 2/12/2008 1:31 PM >>>
Does anyone know if USGBC is allowing credit for CO Control of parking garage ventilation?  If anyone has any experience with successfully getting credit for this efficiency measure can you please let me know.  I am curious what is considered a reasonable baseline.
 
Dear Colleagues;

Short answer: I sure hope not!
 
I very much believe the "reasonable" baseline is CO sensors, so you would schedule the airflows (thus power, if all goes correctly in model land) proportional to some assumed activity schedule. (There is a good summary of what those flows might be in an ASHRAE Jrnl that's about ten years old but on the AJ website.)  CO control is pretty much SOP; I think the IMC, or one of the codes around here, went up to 1.25 cfm/sf constant venting unless CO sensors are used; pretty much assuring everyone uses sensors. There may still be a code req'd floor on the min vent rate even w/sensors. And, in all but the smallest garages, staged fans are typical. MAYBE someone could invent some rationale that if there were some long ducts serving a deep garage, then VSD fans might have a SLIGHTLY lower operating W/cfm and closer tracking of actual req'd dilution air. But not by much.
 
Sure it sounds like "DCV" and the PRM sez we can take credit for that; but we would be creating a baseline considerably worse than typical construction, even 5-10 year old construction. And certainly we can't use 0.7 W/cfm in this baseline. This is why when we get proposals from savvy clients, they specify bldg maximum Btu/sf or kWh/sf or emissions/sf; not some "savings" vs. an artificial baseline. 
 
Fred
 
P.S. Today's Puzzler: What ASHRAE PRM category does a heated parking garage fall into? Does it matter if the heating capacity is more than the semi-conditioned space Btuh/sf rate? 

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