ASHRAE Applications recommends a minimum of 4 ACH for natatoriums. Applying that minimum to my Proposed leads to a somewhat oversized pool unit compared to the Baseline system, which reduces my savings a lot. I couldn't find a code requirement of a minimum amount of ACH, which would allow me to size the Baseline with the same number of 4 ACH. Is somewhere aware of any such code requirement?
A related question: would LEED allow to size the Baseline at 4 ACH, even though the project is not a school?
Thanks for chime in,
Demba Ndiaye, Ph.D., P.E., LEED AP BD+C, BEMP
Dear Demba,
Airflow is only one of the comparisons for a pool. The others, all very powerful in impact, are de-humidification, and heat recovery from the refrigeration system for reheating and pool water heating, and heat recovery for outdoor air preheating.
James V Dirkes II, PE, BEMP, LEED AP
Demba,
In previous versions of LEED, I think you could consider the pool a process
load and model the natatorium as an empty space. Now that you need to
include process loads, perhaps you can have the reference and proposed equal
unless you are trying to claim savings as Jim mentioned.
Aaron Smith, P.Eng
In a recent LEED project with a pool, my assumptions were:
* The Aquatics space requires special temperature and humidity for 24/7 schedule, and thus merits use of a "non-predominant" special Baseline (System #3 or #4)
* The Baseline system (#3 in this case) used the standard delta T, fan power, etc.
* The Proposed system used hot gas reheat, a standard (80%) efficiency boiler for additional heating, heat recovery for the minimum outdoor airflow, and heat recovery from hot gas (if available after reheating) for pool water heating
* Pool water heating, including pool wall conduction loads and pool pumps were considered "process" loads
* Results were favorable!
James V Dirkes II, PE, BEMP, LEED AP
Thanks Guys,
I appreciate your comments.
I use System 3 as recommended by Appendix G for pool space conditioning. Evaporation load is included. Relative humidity is maintained to max 60%. But still, the sizing I get for the Baseline remains below 4 ACH. I would like to find backup material to make the case that the Baseline should use 4 ACH as the Proposed. Equitable? Or maybe not?
Any more ideas?
Regards,
Demba.
Dear Demba,
For the pool I recently modeled, I did not make the Baseline airflow anything different than what was auto-sized at 20F delta T. However, you have caused me to think about this further and it seems that perhaps Exception c. for G3.1.1 may apply to you if the pool's airflow rate can be argued to be "code-required" at 4AC. If I had thought of it, I think I would have done this. As it is, we just received comments back from GBCI, and with 38% savings already, I don't think I will "rock the boat".
If the baseline HVAC system type is 5, 6, 7, or 8, use
separate single-zone systems conforming with the
requirements of System 3 or System 4 (depending on
building heat source) for any zones having special pressurization
relationships, cross-contamination requirements,
or code-required minimum circulation rates.
James V Dirkes II, PE, BEMP, LEED AP