[Bldg-sim] Modelling diversity in single zone apartments

[Jim Dirkes]

Patrick,
Here are a few considerations:

1.       Apartments for working people will have low loads during the day and high loads at night.  The offices will have the reverse pattern.  Depending on the actual office schedules, the actual residential occupancy pattern and the ratio of office / residential space, 50% might work very well.  50% may also be rather close to "irresponsible" unless the local population is very tolerant of room temperatures that are a few degrees higher than normal!

2.       Regardless of #1 above, a LEED project should model the building based on the architect and Engineer's "Basis of Design" (BOD) document.  The scheduling and diversity patterns I mention in #1 are not commonly part of a BOD document, but in your case they sound critical.  You should (strongly) request this information!  If you make assumptions that differ from the Engineer's you may spend endless hours trying to reduce unmet cooling load hours (and probably will not get paid for them)

3.       Once you are confident of the schedules that have been assumed by the BOD, you should be able to represent them for the energy model.

Note: Because each apartment has two fan coils, each with a thermostat, you really have two zones.  This may become important for the cooling diversity.

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Aaron Smith
Sent: Friday, November 29, 2013 6:49 PM
To: Patrick Bivona; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Modelling diversity in single zone apartments

Patrick,

I suspect they didn't assume that the bedroom wasn't cooled at the same time as the living room. They may have assumed that the cooling schedule of the office space is different than the apartments - maybe 8am to 5pm M-F  for the offices and close to the opposite for the apartments. Or they may have determined that the building peak load was 50% of the sum of the individual loads. A more likely scenario would be that the combined affect of both of those might equal 50%.

I don't think it would be acceptable to turn cooling off in half of the apartments even if you did the same thing in the Baseline building. Are you running into issues with the chiller being undersized?

Aaron


From: Patrick Bivona
Sent: Thursday, November 28, 2013 23:32
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] Modelling diversity in single zone apartments


Hi all,

I'm modelling a mixed office/residential tower building with 160 apartments in tropical climate, for LEED. The apartments are centrally cooled with fan coil units, in the living room and bedrooms. The design team sized the chiller with a diversity of 0.5, probably assuming that when the occupants are in the living room, they're not cooling the bedrooms or something of the sort.

Given the number of apartments, I modelled each apartment as a single block. I cannot use zone multipliers because of the specific geometry of the building. I have one combined FCU for each apartment, which is of course either on or off. I'm also grouping apartments based on orientation, but that's beside the point.

My question is about an approach to modelling the diversity of use of FCUs in the apartments. With my modelling simplification, I cannot model the diversity of cooling within an apartment. So what would be an acceptable approach?

I can only think of turning cooling off in half of the apartments, though apartments with cooling turned off are occupied and have internal loads. Would a LEED reviewer be ok with such an approach. Or is there a better way?

Thanks,
Patrick




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