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

Joe Huang yjhuang at whiteboxtechnologies.com
Fri Jan 11 12:44:17 PST 2013
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The topic of using actual year versus typical year weather data (please 
note my rant about nomenclature at the end of my post below, with 
apologies to Steve Cornick :-) ) was discussed last October, so maybe we 
need to create a FAQ on this topic ?   which reminds me that ASHRAE TC 
4.2 has a FAQ about various types of weather data and their appropriate 
use ( see http://tc42.ashraetcs.org/faq.html#6 ).  To me, the 
distinction is obvious - if you're evaluating actual building 
performance, use the actual year weather file; if you're evaluating 
hypothetical building performance (as for standards compliance or LEED 
rating), use a typical year weather file.

This topic is separate from the one about the best method to create a 
typical year or calculate design conditions.   This is as much an 
engineering question as a meteorological one, so I'm afraid the insight 
you will get from climatologists will be limited.  When I worked with 
meteorologists in several countries, esp. in the US and China, I was 
struck that the concept of a "design day" or a "typical year" was 
something outside their experience.

I agree that using an actual year weather file to evaluate a building's 
performance is "cherry picking" the data, but is anyone really doing 
that?  Wasn't that why typical year weather files were developed in the 
first place more than 30 years ago?  My interest in seeing the time 
period for developing typical years or calculating design conditions 
reduced from 30 years is because I think the results would then respond 
better to ongoing trends instead of lagging by a decade or more.  It 
would be an easy hypothesis to test and I'm thinking of doing that for a 
selected number of US stations, i.e., create typical years of different 
time periods and see which time period best matched the results for the 
following X number of years.  As for the minimum acceptable number of 
years to create a typical year, that's been implicitly decided by ASHRAE 
TC 4.2 and NREL as either 7 or 8 years.

The idea of a more conservative set of averaged weather data seems 
problematic to me.  It's hard to define what's conservative because it 
would depend on the building as well as the climate, and any effort to 
massage real data would open up a whole can of worms.  You would be much 
better off to simply run the building over the past so many historical 
years, and pick the year with the highest energy consumption to do your 
projection.

Joe

my rant on weather nomenclature (as promised earlier):  I prefer saying 
"typical year"  when talking about the general concept, and use TMY only 
when referring specifically to the TMYX data sets or methodology 
developed by NREL.  I find using TMY as a general term confusing and not 
fair to all the other typical year data sets, such as TRY,  WYEC, IWEC, 
CZXXRV, DRY, etc.  I also find the term AMY odd, as if real weather data 
needed to be branded  (rant over).

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 1/11/2013 9:13 AM, Nick Caton wrote:
>
> 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?
>
> _________________________________________
>
> *Arpan Bakshi *Sustainability Manager
> LEED AP BD+C, ESTIDAMA PQP
>
> *YR&G*
>
> sustainability consulting, education and analysis
>
> 161 Bowery - 4th Floor - NY NY 10002
>
> D 646.704.2880
>
> _yrgxyz.com <http://yrgxyz.com/>_ | facebook 
> <http://www.facebook.com/#%21/pages/YRG-sustainability/109166559111721> | 
> _twitter <http://twitter.com/#%21/YRGxyz>_
>
> 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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> --
> Jason Glazer, P.E., GARD Analytics, 90.1 ECB chair Admin for 
> onebuilding.org <http://onebuilding.org>
> building performance mailing lists
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