[Equest-users] Actual Building Energy Cost

Eric O'Neill elo at MichaelsEngineering.com
Wed Jun 16 14:52:06 PDT 2010


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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