[Equest-users] Actual Building Energy Cost

[Eurek, John S NWO]

Lan,

This is why commissioning is one of the best things you can do for a project.

Commissioning is very very cost effective.

Almost every piece of equipment is tested in the factory before being
shipped.

The building is a piece of equipment with many parts, it must be tested
(Commissioned).

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Li, Lan
Sent: Thursday, June 17, 2010 8:53 AM
To: Eric O'Neill; Nick Caton; David Bastow; aazhari at jainconsultants.com;
equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Actual Building Energy Cost

In one of my learning course, the instructor mentioned that after they used
eQuest simulated an existing campus, they were not able to have the
simulation results to match utility bills close enough. It turned out that
the economizer damper was on all the time and the some meters were set up
wrong which leads the historical data was inaccurate.  

 

Lan 

 

Lan Li, PE

Mechanical Engineer

Scheeser Buckley Mayfield LLC                                     

1540 Corporate Woods Parkway

Uniontown, OH 44685

Phone: (330) 896-4664 ext. 123

Cell: (330) 904-6292

Fax: (330) 896-9180

lli at sbmce.com <mailto:lli at sbmce.com> 

www.sbmce.com <http://www.sbmce.com/> 

 

Columbus Branch Office (614) 448-1498

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________________________________

From: Eric O'Neill [mailto:elo at MichaelsEngineering.com] 
Sent: Thursday, June 17, 2010 8:11 AM
To: Nick Caton; David Bastow; aazhari at jainconsultants.com;
equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Actual Building Energy Cost

 

Nick,

 

I should make it clear that my initial questions weren't meant to drill
David. I'm genuinely interested if the DOE projects required an extremely
high level of technical accuracy on the input side. (Although they were also
somewhat of a reaction to those requirements.) We have this discussion in our
office every so often, and I'm usually somewhat on my own, but I'm still not
convinced.

 

Would you mind elaborating a little more about why you feel this to be true:

 

"HOWEVER:  The concept of building a model for an existing building, whose
modeled energy consumption/costs fall within a 1-2% of historical utility
records, is entirely feasible - and a reasonable requirement if the goal is
to generate a model for predictive purposes." 

 

So let me ask it this way. Let's say you've got a model, and it's coming in
about 6% low (both heating and electric), but to the best of your knowledge
everything is set up properly. You've got to start making some educated
guesses to close the gap. Do you assume the boiler needs a tuning (drop your
efficiency a few percent) and the AHU coils need to be cleaned (bump up your
static)? Or do you bump up your infiltration slightly (because it's probably
not a very tight building). Or did some maintenance guy came along and
switched on both the boiler pump manually on when he got a cold complaint,
and no one returned them to auto? Or maybe you have data from a few years
with abnormally warm summers and cold winters. I could go on practically ad
nauseum. There's just so many things that can be wrong with an existing
building, as all of you probably know.

 

Whatever you choose, that guess you make may interact (or lack an
interaction) with some measures you're predicting. So, predicatively, what
makes a 1-2% off model better than a 5-6% off model unless you really spend
the time and find out whether your inputs are accurate? 

 

Cheers,

 

Eric

 

From: Nick Caton [mailto:ncaton at smithboucher.com] 
Sent: Wednesday, June 16, 2010 5:43 PM
To: Eric O'Neill; David Bastow; aazhari at jainconsultants.com;
equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Actual Building Energy Cost

 

While I (and I am sure many others) have books to write regarding my thoughts
on the topic, I think I might suggest a simple step back:  The concept of
predictively modeling to within a few percentage points of accuracy is
ridiculous.  There are simply way to many things that could not be known.
HOWEVER:  The concept of building a model for an existing building, whose
modeled energy consumption/costs fall within a 1-2% of historical utility
records, is entirely feasible - and a reasonable requirement if the goal is
to generate a model for predictive purposes.  How often such predictive
models' accuracy is misinterpreted is something I get depressed to think
about.

 

I haven't done the DOE-modeling work that's being referenced with such
requirements, but I have done work for educational clients (physics/building
science departments) who wish to get these models set up for ongoing
study/tweaking purposes.  The exercise is challenging, and as close as energy
modeling gets to "fun," when you can rest at ease knowing the client is fully
on board with what the model is and isn't.  

 

It's fully rational to squirm and cringe when you have to make models that
you know will be mis-used and mis-understood, despite your best efforts.
Fortunate is the practicing energy modeler who gets to work for fully
educated clients and design teams all the time =).

 

Rather than drill David, I think it would be safe to assume those DOE
requirements exist to calibrate a model to a given degree to whatever
historical records are available, NOT to mandate a level of accuracy for
predictive purposes.  If I'm wrong, I hope that work never crosses my desk!

 

~Nick

cid:489575314 at 22072009-0ABB

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Eric O'Neill
Sent: Wednesday, June 16, 2010 4:52 PM
To: David Bastow; aazhari at jainconsultants.com;
equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Actual Building Energy Cost

 

How much effort was put into minimizing the error of your inputs to justify
that level of accuracy in your output? For example, did you convert real
weather data for the two years and use an average of the simulations? Were
you modeling small buildings so you could get a fairly reasonable
infiltration rate empirically? Were occupancy schedules trended, and for how
long? Were all the systems and controls working correctly, with all sensors
calibrated regularly? 

 

1 to 2% seems to me to be fairly unreasonable. Unless you do an amazing job
verifying your inputs, in my opinion that level of precision doesn't get you
a better model. If you set everything up as best you can and it comes in
there, great! But a correctly set up model can be off by over 2% because of a
couple "El Nino" years, a facilities guy locking a humidity high limit to 50%
for a summer, or any number of operational factors. On the other side of it,
we've tried to match a simple DOE2.2 model to a DOE2.1e model with limited
success (I don't think we got within 3%, although we didn't spend too much
time with it). Who knows what the difference would be with E+.

 

I know I always squirm when I'm asked to do existing building models, and it
may be irrational. Heck, if the DOE is asking for 1-2%, I probably am being
irrational. But it seems to me that the error from assumptions could easily
swing a model 1-2% (what would a 30% error on your infiltration do to an
otherwise correct building?). What are other people's thoughts? 

 

Eric

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of David Bastow
Sent: Wednesday, June 16, 2010 3:48 PM
To: aazhari at jainconsultants.com; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Actual Building Energy Cost

 

On all the DOE modeling projects that we have done, of an existing building,
they have required the model to be within 1 to 2% or less of the actual
energy usage, based on an average two year history.  Is that what you are
talking about?

 

David A. Bastow 

McClure Engineering, Inc.  

 

 

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ahmed Azhari
Sent: Wednesday, June 16, 2010 12:10 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Actual Building Energy Cost

Hi all, 

 

Does anyone have a ballpark percentage of the actual annual energy cost
versus the modeled annual energy cost for a building?  

 

Thanks,

__________________________________________________________________________

Ahmed Azhari, B.Eng., LEED(r) AP

Energy Analyst

 

Jain Sustainability Consultants Inc.

 

2260 Argentia Road, 2nd Floor

Mississauga, Ontario L5N 6H7, CANADA

Tel:  (905) 542 7211 Ext 234

Fax: (905) 542 7622

Email: aazhari at jainconsultants.com <mailto:aazhari at jainconsultants.com> 

Web: www.jainassoc.com <http://www.jainassoc.com/> 

 

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