[Equest-users] Unexpected Custom SHGC Results
Peter Baumstark
pbaumstark at sbcglobal.net
Sun Jul 15 17:47:48 PDT 2012
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 LBLwindow does glass U-value not shading, ware-as
>LBLoptics 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
>
>
>
>
>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, CA 94556 (o) (925)388-0265 (c) (510)928-2683
www.whiteboxtechnologies.com "Building energy simulations at your fingertips"
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