[Equest-users] Unexpected Custom SHGC Results

CleanTech Analytics jeremiah at cleantechanalytics.com
Sun Jul 15 18:51:59 PDT 2012


So if the curve theory is correct I wonder if this would happen in other
modeling software  or more importantly in the real world>?  --reduce
internal gain and increase cooling consumption--  or if this phenomena is
only possible in the virtual world of eQuest..,,

Joe-Liam-Paul what do you think >?<


*Jeremiah D. Crossett*
*CleanTech Analytics*
*503-688-8951*
*www.cleantechanalytics.com* <http://www.cleantechanalytics.com>


*

This document may contain valuable information proprietary to CleanTech
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On Sun, Jul 15, 2012 at 5:47 PM, Peter Baumstark
<pbaumstark at sbcglobal.net>wrote:

> It's an interesting problem.  With this model, no matter what I do, if I
> manually change the SHGC or SC (if I use the U-Value method), or if I
> select different glazing types from the library (with different SHGC
> values), no matter what face of the building I change it, I get an increase
> in overall monthly energy use with a lower SHGC.
>
> I built the model through a zone by activity area method that pretty
> closely matches the various zones of the building.  It's a VAV with
> terminal reheat system (1995 Trane Intellipaks), and I entered actual
> economizer, static pressure and SAT settings.  Airflow matches as-built
> design drawings.
>
> I tried using other eQUEST models I've built for other customers using
> similar methods, changed the location to San Jose, and ran window cases and
> results were as expected.
>
> I'm coming to believe that one issue with the building in question is the
> RTUs seem over sized relative to the use patterns and internal heat gains.
> This building previously had various lab areas, then was purchased by
> another customer with lower internal heat load rates, but they kept the
> same RTUs.
>
> Could it be possible that the lower heat gains from better fenestration
> products could place the RTUs at a more inefficient spot on its performance
> curve?  I've ran into similar issues with chilled water systems, but never
> looked at DOE-2 performance curves for DX units.
>
> Pete
>
>
> ------------------------------
> *From:* Paul Diglio <paul.diglio at sbcglobal.net>
> *To:* Joe Huang <yjhuang at whiteboxtechnologies.com>; CleanTech Analytics <
> jeremiah at cleantechanalytics.com>
> *Cc:* equest-users at lists.onebuilding.org
> *Sent:* Sun, July 15, 2012 5:03:54 PM
>
> *Subject:* Re: [Equest-users] Unexpected Custom SHGC Results
>
> Joe:
>
> I agree.  I find the comment to be more than mildly offensive.
>
> I have the same experience that funky modeling results usually are the
> result of flawed inputs or depending on too many eQuest defaults.
>
> Paul Diglio, CEM, CBCP
>
> 87 Fairmont Avenue
> New Haven, CT 06513
> 203-415-0082
>
>
> www.pdigliollc.com
>
>
> ------------------------------
> *From:* Joe Huang <yjhuang at whiteboxtechnologies.com>
> *To:* CleanTech Analytics <jeremiah at cleantechanalytics.com>
> *Cc:* equest-users at lists.onebuilding.org
> *Sent:* Sun, July 15, 2012 7:21:54 PM
> *Subject:* Re: [Equest-users] Unexpected Custom SHGC Results
>
> I've found this comment to be mildly offensive as well as showing a lack
> of understanding about how heat gains ultimately get translated to cooling
> energy consumption.  It's extremely hard for me to believe that eQUEST or
> DOE-2 has been flawed for 25 years in modeling something as fundamental as
> solar heat gain through windows.  In all the decades I've used DOE-2 to
> analyze window performance for DOE's EnergyStar Program as well as numerous
> other projects, whenever the results did not match or ran counter to
> first-principle expectations, it was always because there was some other
> factor that have been overlooked or ignored, chief among them being the
> size of the HVAC system, its configuration, and control strategy.
> Locations with mild cooling loads, such as San Jose,  are particularly
> sensitive to such system interactions.  Were both runs done using
> "autosizing"?  What
> kind of a system was modeled - VAV or CAV ?   Did the model have an
> economizer?   What were the HEAT-CONTROL and COOL-CONTROL strategies ?
> etc.   It's far too early to lay blame on the DOE-2 algorithms.
>
> Joe
>
> On 7/14/2012 1:41 PM, CleanTech Analytics wrote:
>
> Just admit it- eQuest is flawed, you don't have to make up things to
> protect it-
>
>  If it is a mistake to use the percent points rather then percent reduced
> from the abrataty eQuest assumption from 1999 window specs than the it
> should have reduced solar heat gain by more then his product even provided-
> Using the 33 percentage points but used the 33% should have provided him
> over stated cooling reduction, (and extra added heating consumption
> tradeoff)
>
>  O- and FYI LBL window does glass U-value not shading, ware-as LBL optics
> can be used for film coefficients and used to create a custom glass type in
> window, but do not do any calculations for "shading"
>
>  I say you try the same model in Energy Plus or TRNSYS and see if the
> results differ.
>
>
>  *Jeremiah D. Crossett*
> *CleanTech Analytics*
> *503-688-8951*
>  *www.cleantechanalytics.com* <http://www.cleantechanalytics.com>
>
>
>   *
>
> This document may contain valuable information proprietary to CleanTech
> Analytics which is private and confidential. It may not be shared, copied,
> stored or transmitted in any form without the prior written consent of
> CleanTech Analytics
> *
>
>
>
> On Sat, Jul 14, 2012 at 12:42 PM, Liam O'Brien <obrien_liam at hotmail.com>wrote:
>
>>  Hi Pete,
>>
>>  I don't have a ton of experience with detailed modelling of shades in
>> eQUEST, specifically, but two things that could be at play:
>>
>>  - The claim from the manufacturer sounds like it's not intended to
>> universal in absolute terms. Also, it would be more conservative to reduce
>> the SHGC by 33 percent than 33 *percentage points* (as you did) if
>> you're going to take this simplified approach. Therefore, it would be
>> closer to SHGC=0.44. Subtle but significant. You could try using software
>> that specializes in window/shade performance like LBNL Window or Parasol to
>> try to characterize the performance of your specific shade-glazing
>> combination
>> - Depending on the operating conditions and construction of the building,
>> there's a chance your results aren't ridiculous. If shades intercept
>> transmitted solar radiation, then a lot of that energy will almost
>> immediately transfer to the air via convection. If you have thermally
>> massive interior surfaces, there's a chance your building could actually
>> perform better without those shades because the air conditioning won't kick
>> in till later.
>>
>>  Liam
>>
>>  ------------------------------
>> Date: Sat, 14 Jul 2012 11:51:02 -0700
>> From: pbaumstark at sbcglobal.net
>> To: equest-users at lists.onebuilding.org
>> Subject: [Equest-users] Unexpected Custom SHGC Results
>>
>>
>>  Hello,
>>
>> I have an "L" shaped building with the point of the "L" facing North.
>> The inside of the "L" has both NE and NW surfaces, that include a high
>> amount of glass, which heats up the perimeter building spaces considerably
>> during the summer.  Glazing is single pane tinted.
>>
>> The customer wants to install some Verisol SilverScreen shades in these
>> windows.  According to the manufacturer, the SHGC will reduce by about
>> 33%.  I modeled in eQUEST, window properties in these windows to have an
>> SHGC of 0.67 and ran an EEM reducing SHGC to 0.34, and got an increase in
>> cooling load and fan load year round, even in the summer months.
>>
>> Am I seeing this wrong?  I can't figure out how I could possible get
>> results like this?
>>
>> Thank you,
>> Pete
>> San Jose, CA
>>
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>
>
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> --
> Joe Huang White Box Technologies, Inc. 346 Rheem Blvd., Suite 108D Moraga,
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