[Equest-users] Fwd: Composition of weather file data

David Eldridge DEldridge at grummanbutkus.com
Tue Feb 11 18:27:11 PST 2014

Joe, you aren't performing "p-RCx energy models" very often?

But seriously Arunabha, the magnitude of RCx savings for a facility may not be a high percentage of the total usage - although the measures are low-cost and quick payback - energy modeling used as part of RCx should try to use actual weather data if possible or else the variances due to weather might be the same magnitude as the RCMs if you are attempting any significant level of calibration for the model.

However you should then run the proposed case with typical weather in order to model an "expected" annual savings.

Depending what measures you are modeling and whether you have any calibration data during the "p-RCx" phase, typical weather could work well enough, at least to get started and see if you should continue using the model for this purpose.


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

From: Joe Huang [mailto:yjhuang at whiteboxtechnologies.com]
Sent: Tuesday, February 11, 2014 2:43 PM
To: Arunabha Sau; David Eldridge; equest-users at lists.onebuilding.org
Subject: Re: Fwd: Composition of weather file data

It's inevitable that the peak conditions will fluctuate from year to year, that's just the chaotic nature of the weather.  If you
use a "typical year" weather file, you will tend to get, but not necessarily, an average annual peak, since the months have been selected to best match the long-term distribution of temperatures, humidity, solar, wind speed, etc.

What is pre-RCx ?  "pre retro-commissioning"?  What is that?  Too many adjectives for me :-)

In any case, if you're modeling an existing building to assess its historical performance, I would definitely use actual year weather files.
As for where to find such data, there's a proliferation of sources on the Web, although most would require processing to turn them into formats required by simulation programs such as eQUEST, etc.

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 2/11/2014 4:09 AM, Arunabha Sau wrote:
Thanks Joe & David.
Appreciate your explanation. It was very through.
In an EPW file, I saw only 1990's data, so I was worried about the peak if the typical years's data would be different or so! I was modeling for pre-RCx. So, I was more concerned about actual (or near to actual) heating/cooling load.
For Cx modeling, do you guys make model out of these weather file or make a more customized weather file from some online available weather file source or buy one?

Best regards,

Texas Aggie '10
JU, Kolkata '05

Try not to become a man of success, but rather try to become a man of value.

- Albert Einstein

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