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

Maria-Lida Kou marialidakoun at gmail.com
Thu May 21 07:17:16 PDT 2015


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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