[Bldg-sim] Modelling diversity in single zone apartments

Patrick Bivona patrick.bivona at gmail.com
Mon Dec 2 08:05:30 PST 2013


Hi,

Thank you all for your answers. I may have confused everyone. The design
team used a diversity of 0.5 for the cooling equipment in the apartments
only. They haven't assumed this for the whole building.

Still, knowing that these are high-end apartments, I'm not entirely
convinced that people will turn cooling off when they don't occupy a space.
But if that's the assumption, I should go with it, right?

I had a look at the high-rise office/apartment model Dru pointed me to.
It's interesting to note that the apartments are modelled as single-zone
with cooling running 100% time and no setback.

So in conclusion, if I want to stick to the assumption of the design team,
I should split the apartment in 2 zones so that the FCUs in bedrooms and
living rooms can have different operation schedules.

Cheers,
Patrick



On 2 December 2013 06:49, Dru Crawley <dbcrawley at gmail.com> wrote:

> You may also want to look at the multifamily building models that PNNL
> uses for evaluating 90.1 changes:
>
> http://www.energycodes.gov/development/commercial/90.1_models
>
> (towards the bottom of the table). The 'Scorecard' XLS shows all the
> inputs and where there were derived.
>
>
>
>
> On Sun, Dec 1, 2013 at 6:22 PM, Jim Dirkes <
> jim at buildingperformanceteam.com> wrote:
>
>> 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
>>
>> *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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