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

[Eric Ringold]

The text of Appendix G states this explicitly in Section G1.2, Note 2:

"Neither the *proposed building performance* nor the *baseline building
performance* are predictions of actual energy consumption or costs for
the *proposed
design* after construction. Actual experience will differ from these
calculations due to variations such as occupancy, building operation and
maintenance, weather, energy use not covered by this procedure, changes in
energy rates between design of the building and occupancy, and the
precision of the calculation tool."


On Thu, May 21, 2015 at 10:42 AM, Brooks, Alamelu <Alamelu.Brooks at icfi.com>
wrote:

>  I believe Appendix G is not meant to measure the performance of the
> existing building. ASHRAE 90.1 Appendix G Technical Committee is the right
> source to answer this question. They can clarify the intention of the APP G
> modeling methodology.
>
>
>
> Best,
>
> Alamelu
>
> Alamelu  Brooks LEED AP (BD+C), HBDP, BEAP, EIT| Senior Associate |
> +1.443.718.4881 direct | Alamelu.Brooks at icfi.com | icfi.com
>
> ICF INTERNATIONAL | 7125 Thomas Edison Drive, Suite 100, Columbia, MD
> 21046 USA
>
> Connect with us on social media <http://www.icfi.com/social>.
>
>
>
>
>
> *From:* Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] *On
> Behalf Of *Jim Dirkes
> *Sent:* Thursday, May 21, 2015 10:36 AM
> *To:* Nathan Kegel
>
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Comparing ASHRAE 90.1 App G Models to Real
> Buildings
>
>
>
> 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:
>
>   415.420.9314
>
> http://www.iesve.com
>
> Integrated Environmental Solutions Limited. Registered in Scotland No.
> SC151456
> Registered Office - Helix Building, West Of Scotland Science Park, Glasgow
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>
> Email Disclaimer <http://www.iesve.com/disclaimer.html>
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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
>
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>
> 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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-- 
Eric Ringold
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