[Equest-users] Unexpected Custom SHGC Results

[CleanTech Analytics]

Good points Joe- Counter-intuitive but your opinion carries the weight of
many years of experience I do not have, and did not think of. My opinion is
that there are issues with eQuest that have been left un-checked, but
no-one knows what they are- so my bad for assuming that this is one of them.

Best regards


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


*

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On Sun, Jul 15, 2012 at 4:21 PM, Joe Huang <yjhuang at whiteboxtechnologies.com
> wrote:

>  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,
> CA 94556 (o) (925)388-0265 (c) (510)928-2683 www.whiteboxtechnologies.com"Building energy simulations at your fingertips"
>
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