[Equest-users] How detailed is necessary

Charudatta Joshi cjoshi.energy at gmail.com
Thu Mar 5 17:20:52 PST 2015


Good points Nick and Christopher. The level of detail depends on a
combination of numerous things, some of which are goal/s of modeling,
design and complexity of systems, skill level of the modeler who'll work
the most on that project (especially if model will be shared with others
having different use for it), and time available. Risk:reward like Nick
said.

There are several comments and graduate theses suggesting that more detail
does not always mean better accuracy. Depending on the sensitivity and
scope of ECMs, a simple model can point to the same decisions as a detailed
one, so long as there's consistency in the magnitude of error (judging that
is another discussion; both models could be equally misguiding).

However, sometimes it's hard to tell what a model could be used for past
the first goal. Say you set up a model with sufficient detail for EAc1, and
then a while down the line you need to calibrate it with post occupancy
data. Can you use the same model without major time consuming adjustments,
or must you spend time nearly equivalent to making a new model, before you
can compare your hourly results? Just need to be future proof to whatever
extent possible.

In companies with several modelers, it's probably better to make detailed
models, unless your team uses very similar styles, is great with
documenting methods and keeps project specific notes understandable to
others. Picking up somebody else's model could be troublesome. Not helpful
when your 3D view looks nothing like the real building to the new modeler.
Technically fine otherwise.

Ideally, if you could closely match your zoning and other inputs to the
ME's design, that seems to work well more often than not. YMMV. Also helps
to look at the M&V plan if it exists; and if not, bring it up for
discussion with the owner / ME. Many people on this list use some process
automation (VBA, Python, Ruby etc.) to speed things up, which is immensely
helpful to create and manage more detail in the same available time ,
assuming that detail influences outcome (plus it let's you fight
confirmation bias).

CJ
On Mar 5, 2015 7:48 AM, "Jones, Christopher" <cjones at halsall.com> wrote:

>  Nick’s comment brings up a question.  I am interested in others’
> opinions on “how detailed is necessary” in reference to combining spaces.
> I tend to combine spaces to reduce the number of zones in the model.  For
> example, I will combine a group of interior offices with adjacent
> washrooms, storage rooms, and other service spaces with exhaust only.  I
> know others will define each of these spaces individually significantly
> increasing the number of spaces/zones in the model.
>
>
>
> The benefit of combining spaces is to reduce the time it takes to draw the
> spaces in eQuest.  This helps to reduce the complexity of the model and the
> run time.
>
> The drawback is that you have to sum the lighting, process loads, and HVAC
> inputs, etc.  I use pivot tables to do the summing for me.
>
>
>
> Any thoughts appreciated.
>
>
>
> *Christopher Jones**,* P.Eng.
> Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527
>
>
>
> *From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
> Behalf Of *Nicholas Caton
> *Sent:* Thursday, March 05, 2015 1:48 AM
> *To:* Anura Perera; equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Modelling thermal zone with multiple AHUs
>
>
>
> Hi Anura,
>
>
>
> If the individual systems do not act independently, or otherwise are not
> expected to handle substantially different load profiles through the year
> (consider beyond internal loads: do some zones have differing skin loads?),
> then it’s probably safe to combine systems.
>
>
>
> In my experience, I would however caution this particular approach of
> combining systems to streamline your model development has potential to
> backfire.  The time you save in the short term with inputs could be lost to
> processing those system inputs (creating & documenting those
> heating/cooling/airflow capacity sums and weighting associated unitary
> efficiencies) and perhaps also in troubleshooting/re-constructing the model
> if you find out later the assumption of identical system behavior was
> off-base.  On the other hand, the extra time you would spend setting up
> each individual system could be better invested elsewhere in the modeling
> process to create a better final product (or towards getting home on time)!
>
>
>
> In my mind, this sort of “how detailed is necessary” decision is a matter
> of risk:reward.  It’s a regular category of judgments that pop up all the
> time in new work.  Being able to recognize and explore opportunities for
> acceptable approximations is a defining trait for experienced modelers.
>
>
>
> Insofar as LEED reviewers are concerned, I have anecdotally combined
> systems (documenting them as such with supplemental language) without
> incident in past projects.
>
>
>
> Kind regards,
>
>
>
> ~Nick
>
>
>
> *NICK CATON, P.E.*
> *Owner*
>
>
>
> *Caton Energy Consulting*
>   1150 N. 192nd St., #4-202
>
>   Shoreline, WA 98133
>   office:  785.410.3317
>
> www.catonenergy.com
>
>
>
> *From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
> Behalf Of *Anura Perera
> *Sent:* Wednesday, March 04, 2015 4:01 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Modelling thermal zone with multiple AHUs
>
>
>
> Dear All,
>
>
>
> I am modelling a building having thermal blocks with multiple thermal
> zones. Each thermal zone has an AHU. The floor level internal loads are
> evenly distributed. As such I am planning to model the thermal block
> considering all AHUs in the thermal block as lumped into one large AHU with
> total capacity of all individual AHUs of zones in the block.
>
>
>
> Will this be an acceptable approach for LEED reviewers?
>
>
>
> Any experience to share please?
>
>
>
> Thanks in advance
>
> Anura
>
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