[Bldg-sim] Binned weather data for US (not the equest weather file)

Nick Caton ncaton at smithboucher.com
Fri Jan 11 09:13:40 PST 2013
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I'm personally a big proponent for modeling location-specific AMY weather whenever there is calibration to historical data to consider, but that certainly doesn't apply to every model or standard.  I don't consider AMY/TMY to be an either-or proposition as much as it makes sense to use either as appropriate to the analysis at-hand.

I have myself used both kinds of weather files with the same model, to different ends.  If you are trying to make long-term ROI decisions, averaged weather data is absolutely preferable to AMY as you don't want to over- or under-account for the weather extremes that occur over any given period in isolation.  If you are calibrating an existing building to past utility bills and measurements, that calibration can be performed with much more certainty using AMY.

As to using 30+ years of averaged data vs. a smaller averaged set of more recent data for TMY, taking any position on the matter seems like "timing the market" on some level to me...  I'm very curious to hear the opinions of the weather scientists and researchers more informed than myself.  I wonder (out loud) whether we should consider the anticipated lifespan of the building and how long the owner will be paying the utility bills in making such a decision on a per-project basis?  Perhaps a school district occupying the same building for many decades is better served making decisions with a more conservative set of averaged weather data (not necessarily "shorter," but with amplified extremes)?

So far as LEED/standards like the 90.1 performance rating method are concerned, I think TMY remains preferable to AMY to avoid "cherry picking" a year which would benefit the demonstrated performance.  I don't think the duration of years involved in the TMY data should at least have some minimum (if that's not spelled out somewhere already), if not an explicitly required number of years, for the same reasons.

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Arpan Bakshi
Sent: Friday, January 11, 2013 10:22 AM
To: Chuck Khuen
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Binned weather data for US (not the equest weather file)

We have some good discussion at the NY IBPSA meeting last night about TMY vs. AMY weather data, and looking at both on projects even though AMY data is not common in U.S. standards / rating systems.

Any thoughts here? Do others run concurrent simulations using AMY data?





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YR&G
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On Fri, Jan 11, 2013 at 11:15 AM, Chuck Khuen <chuck.khuen at wxaglobal.com<mailto:chuck.khuen at wxaglobal.com>> wrote:
I agree with Joe's assessment here on the length of time for a TMY file. Since we construct TMY files on demand, we are actually thinking about making the number of years a user selectable variable..."Build from the last ___ years of data".  Would that be useful?

Chuck

_________________
Chuck Khuen
Co-Founder, EVP
Weather Analytics
weatheranalytics.com<http://weatheranalytics.com>
781-856-5383<tel:781-856-5383>

-----Original Message----- From: Joe Huang
Sent: Thursday, January 10, 2013 4:48 PM
To: Alec Stevens
Cc: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] Binned weather data for US (not the equest weather file)

Here are my two-cents:

I think the idea of calculating design conditions or developing "typical year" weather data
using a long historical record, e.g., the past 30 years, needs to be re-evaluated in light of
global or regional climate change, as well as such irreversible trends as Urban Heat Islands,

Using longer time periods doesn't bring more accuracy in predicting future climate conditions
(after all, aren't we interested in only how buildings do in the future, and not the past?),
but only anchors us more in the past.

About 15 years ago, a meteorologist in ASHRAE TC 4.2 found that you need only 7 years
of data to overcome the stochastic year-to-year variations in the climate. Therefore, I feel
that it's best to use a shorter time period, more like the last dozen, for these purposes.

That's what I've done for the California Energy Commission in creating the new CZ2010 Title-24
weather files, and what I will be doing to calculate design conditions for the same locations.

There's also been discussion in various places on using GCM (Global Circulation Models) to
calculate future weather and then develop design conditions or "future year" weather files.
I find these  methods too hypothetical for my tastes, and I'm sure those skeptics out there
would have a field day if we were to use them, so my position is to keep doing things the
old way with the actual historical data, but shorten the time periods to something more
immediate.

Last year, I did a study of the savings for window awnings,  where the client asked me to also
do the simulations using the hottest year over the past decade.  The results were quite
noticeable.
The hottest year (judged by cooling degree-days) for 40% of the 50 US locations I studied were
in the last two years (2010 or 2011).  The cooling loads in many locations increased by 30-40%
(more in the north, less in the south).

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>
www.whiteboxtechnologies.com<http://www.whiteboxtechnologies.com>
(o) (925)388-0265<tel:%28925%29388-0265>
(c) (510)928-2683<tel:%28510%29928-2683>
"building energy simulations at your fingertips"


On 1/10/2013 1:03 PM, Alec Stevens wrote:
Here's some food for thought (and sorry to hijack this thread):

I was at an AEE meeting yesterday that included a discussion by a local
meteorologist about the increased variability and extremes that are being
predicted in weather models for the future (i.e. climate change).

What is the feeling in the bldg-sim community as to how useful 1973-1996
binned average data will continue to be when it comes to predicting building
operation, loads, and performance in a future that is expected to be more
variable and extreme with regards to weather?

Is anyone preparing a new set of TMY data with more extremes?  Are design
day criteria being updated from the historical ASHRAE 1% values?  Will 95
drybulb/78 wetbulb (for Boston anyway) no longer be the standard?

Just wondering if our current methods of building simulation (and design)
may leave something to be desired.


Sincerely,
Alec Stevens

DMI
300 Chestnut Street, Suite 150
Needham, MA 02492
p: 781 449 5700 x11<tel:781%20449%205700%20x11>   f:781 449 5710<tel:781%20449%205710>
e: astevens at dmiinc.com<mailto:astevens at dmiinc.com>



-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>
[mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of Jason Glazer
Sent: Thursday, January 10, 2013 3:50 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] Binned weather data for US (not the equest weather
file)

The updated Engineering Weather Data to cover 1973-1996 and put it on a CD

http://ols.nndc.noaa.gov/plolstore/plsql/olstore.prodspecific?prodnum=5005

It is only $17 now.

Jason


On 1/10/2013 2:42 PM, Joe Huang wrote:
What do you mean by binned weather data?  Like what was in the Air
Force Engineering Weather Data manual from 1978?
You might check ASHRAE's Weather Data Viewer that can produce binned
temperature data for over 5,000 locations around the world.  It's not
free, though, costs $119.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>
www.whiteboxtechnologies.com<http://www.whiteboxtechnologies.com>
(o) (925)388-0265<tel:%28925%29388-0265>
(c) (510)928-2683<tel:%28510%29928-2683>
"building energy simulations at your fingertips"


On 1/10/2013 11:48 AM, R B wrote:
Hi All,
Is there a way to get binned weather data for different locations -
preferably free. A quick google search did not come up with anything
concrete.
Thanks
-Rohini


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