[Bldg-sim] Comparing ASHRAE 90.1 App G Models to Real Buildings

Jim Dirkes jim at buildingperformanceteam.com
Thu May 21 07:36:26 PDT 2015


I agree fully with all of the above comments and would like to add these:

   - Even buildings that are commissioned properly will see their
   performance erode over time.  There are hundreds of reason for this,
   ranging from poor maintenance to well-intentioned maintenance people not
   having time to monitor operations well.  There is NO BUILDING that operates
   well for long.
   - Buildings often see changes in operation, occupancy and schedule.
   These are oftimes gradual changes over a period of years, but can be
   substantial


On Thu, May 21, 2015 at 10:22 AM, Nathan Kegel <nathan.kegel at iesve.com>
wrote:

>  Climate files used in the simulations versus the actual weather.
>
>
>
> I’m in the midst of a project that shows a variance in EUI of up to 200%
> just by changing the climate file for the DOE primary school.  Full results
> to be presented in September.
>
>
>
> Add in all the other factors already mentioned, and if your 90.1 model
> comes anywhere close the real buildings’ it’s far more likely that the 90.1
> model was extremely “lucky” than it is that the model used accurate
> assumptions.
>
>
>
> Regards,
>
>
>
> Nathan
>
>
>
> <http://www.iesve.com/>
>
> *Nathan Kegel*
> *Business Development Manager*
>
> O:
>
>   763.276.9981
>
> M:
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>   415.420.9314
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>
> *From:* Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] *On
> Behalf Of *Maria-Lida Kou
> *Sent:* Thursday, May 21, 2015 9:17 AM
> *To:* Jacob Dunn
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Comparing ASHRAE 90.1 App G Models to Real
> Buildings
>
>
>
> Jacob,
>
>
>
> Happy to hear that other people are thinking the same.
>
>
>
> I was into this subject on my own thoughts recently.
>
>
>
> I would like to add in your list: Occupants' behavior actually which is
> not in the stage to be included into the prediction.
>
> I would add commissioning as well along with controls simulation and
> controls operation.
>
>
>
> Apologies because I haven't worked with LEED projects but I think the
> above applied in general to "the performance gap".
>
>
>
> Really looking forward to hearing more about this subject as I am not that
> experienced engineer yet, but really interested in "the performance" side
> of buildings.
>
>
>
> Best,
>
> Maria-Lida Kounadi
>
>
>
>
>
> 2015-05-21 15:04 GMT+01:00 Jacob Dunn <jdunn at eskewdumezripple.com>:
>
>  Bldg-Sim Community –
>
>
>
> I’m trying to compile a list of why it might be inappropriate to compare
> Appendix G models to actual consumption data.  This comes about because I
> recently got into a debate with one of my co-workers when looking at the
> infamous NBI chart/study that shows little correlation to predicted and
> actual energy values of LEED buildings.  I was trying to explain that the
> Appendix G model’s intent is NOT to be compared to actual consumption, as
> it is a modeling protocol aimed at creating consistent relative comparisons
> for LEED points.
>
>
>
> Here are the reasons thus far that support this notion (that App G models
> shouldn’t be compared to actual data).  Does anyone know of any resources
> out there that expand upon this?  Or can you think other reasons?
>
>
>
> -          Appendix G does not take into account external shading, which
> can be critical in urban environments for accurate energy predictions
>
> -          Schedules are typically not created with the intent of being
> predictive.  Overall building hours are adhered to, but detailed schedule
> creation is not usually in the scope of a LEED model (or is it, in your
> experience?).  For instance, typical plug load base values during
> unoccupied times are .3, this is a pretty big assumption.
>
> -          The App G model uses a TMY weather file, which can vary from
> the current weather year (I wonder on average by how much?)
>
> -          Infiltration values are assumed, unless blower door testing
> has been done (which is rare for commercial buildings).
>
> -          Thermostat values are modeled as consistent across the
> building, which is rarely the case in an actual operating building
>
>
>
> Any additional insight is much appreciated!
>
>
>
>
>
> *Jacob Dunn LEED AP BD+C*
>
> *ESKEW+DUMEZ+RIPPLE, APC*
>
> 2014 AIA National Architecture Firm Award
>
>
>
> 365 Canal Street Suite 3150
>
> New Orleans LA 70130
>
> 504.561.8686
>
> *eskewdumezripple.com <http://www.eskewdumezripple.com/>*
>
>
>
>
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-- 

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim at buildingperformanceteam.com

Website <http://buildingperformanceteamcom>l  LinkedIn
<https://www.linkedin.com/pub/jim-dirkes/7/444/413>

 The truth is still the truth, even if nobody believes it.  A lie is still
a lie, even if *everyone* believes it.
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