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LEED Occupancy, design data vs ashrae

asked 2018-12-12 12:25:27 -0500

manfred gravatar image

updated 2018-12-12 12:25:50 -0500

Hi, is there a specific rule for modeling occupancy in the proposed (and therefore in the baseline) leed energy model?

Does it have only to be consistent with the design documents as showed in Table 3.1.1?

What if the declared occupancy is different from Ashrae occupancy? Which one should I use?

The 90.1 do not specify anything else about it.

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answered 2018-12-14 07:11:32 -0500

The general approach I have followed is that the ASHRAE schedules are a great starting point, but probably don't reflect your building/project and therefore should be fit to the project. There can be good to get an owner's rep / architect / team to think about when and how the building will be used. I've done this by providing a 'summary of schedules' to have them mark up and return. Infinitely more successful than the open ended 'so, what are your building schedules?'

We also do quite a few project which there are no ASHRAE typical schedules and have to craft our own (ex: stadiums / sports facilities). As long as Proposed = Baseline and the schedules are reflective/realistic that's probably fine.

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Thank you. With schedule, do you mean both the "peak value" and its hourly variation? Maybe I didn't highlight it, but I meant only the occupancy value (peak).

Gio gravatar image Gio  ( 2018-12-14 07:41:36 -0500 )edit

I have modified both, the peak and the hourly values. They both have dramatic impacts on overall energy. And when we modify schedules, its viewed as a set. aka - occupancy modification must be aligned with lighting, plug loads, fan schedules and setpoints.

dradair gravatar image dradair  ( 2018-12-14 07:53:16 -0500 )edit

Ok so you think you can lower the occupancy and hourly occupation and edit the lighting and plug loads schedules accordingly. I'm a little surprised, but TG3.1.1 do not cite directly occupancy and TG3.1.3 allows to modify the schedules so I do think you are right. @dradair what about the peak value (design value): do I have to use it in the simulation? If not, what is the meaning of unmet hours analysis?

Gio gravatar image Gio  ( 2018-12-15 05:33:46 -0500 )edit
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Yes. The schedules can - and I'd advocate - should be tailored to your building; IF known. If not known (ex: spec office, general strip mall retail), sure generic schedules are fine. But, if there is a known tenant, a known use, known information; that should be used to tailor the use schedules to fit the project. But you must use logic and known information to justify the schedules. For example, a sport stadium will have peak occupancy and little occupancy between events. But if there are operations offices within that stadium, those are most likely used like a more 'typical' office.

dradair gravatar image dradair  ( 2018-12-17 08:01:31 -0500 )edit

(cont) a further, maybe better example. A project is half office and half research lab. The building occupants will have both lab space and office space. The designer must design around either one or the other being full to properly size the capacity and ventilation. And the HDD/CDD/Sizing days in the model should have scheduled to reflect this - BUT the simulation days should consider that the building occupants will either be in the lab OR the office at any given time. Thus, the occupancy and misc loads may vary and will be less than peak in those area. But, the lights will still....

dradair gravatar image dradair  ( 2018-12-17 08:04:21 -0500 )edit

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Asked: 2018-12-12 12:25:27 -0500

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Last updated: Dec 14 '18