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Re: [EnergyPlus_Support] Window5 data file
Results from experiments with window5 files, reversed layering for interior windows and low-E surface location:
I was concerned with the idea of creating a reverse-layer low-E window subsurface for an adjacent window in an interior zone, since each glass material 'layer' actually has its own layers with different spectral qualities (back and front in the material definition). If the same materials are used for the reverse/rotated construction, front becomes back and back, front (outside to inside), and the lo-E surface ends up on the wrong side. Which zone should have the 'real' window definition? Am I thinking about this correctly?
My guess is that a flipped-face, reverse-layer construction (double-negative, so actually a correct order of 1,2,3,4 surfaces) for the interior window of the outboard zone would yield the most 'correct' results, as this is the zone where the exterior conditions (surface temperature, diffuse solar) for the interior zone are determined (??).
If this is correct, the hypothesis would be that because the lo-E coating is on #2 surface for the outboard zone, the Surface Inside Temperature of the interior window of the outboard zone should be warmer than if the layers were the 'wrong' way round. Also, there should be a higher deltaT between the inside and outside surface temperatures in a cooling situation.
I built two pairs of window constructions, one normal (loE on #2 surface) and one reversed (loE on #1 surface). The flipped material puts the loE coating on the correct face for the outboard zone, but not for the inboard zone, while the 'normal' material definition puts it on the correct face for the inboard zone (and is ALOT more intuitive), but not the outboard reversed-layer zone.
The hypothesis above proved out for this test. I'm still a bit uncomfortable with the results, which show about a 9% difference is resultant cooling loads (favoring the non-intuitive flipped-reversed construction) for a 70% glazed space inboard of a 100% glazed double-skin space. There is about 18% difference in Zone Diffuse Solar from Interior Windows (lower for the flipped-reversed material), which makes some sense, as the flipped version in W5 has an SHGC about 5% higher.
One question is, what is used to determine inside surface temperature of the glass in the interior zone, and therefore convection and resultant air heat gains? Is it the exterior temperature of the outboard zone surface? Effective Uvalue for the flipped material construction is significantly higher than for the normal construction, but I believe this is not a useful value to understand the e+ calculations, as the engine is only concerned about material temperatures and conductivities of the layers, right?
Hope someone can clear this up.
By the way, there is a slight difference between doing the same operation using Window5 data files instead of explicit e+ materials and constructions. Is this simply due to the more specific optical data provided in the W5 datafile compared to using the "Spectral Average" optical data type?
And lastly, what happens if a different set of materials are used for the layers of an adjacent surface? ie, can I use a flipped-face low-E glass for one construction, and a non-flipped glass material for the reversed construction? No time for more experiments.
r3
----- Original Message -----
From: David Scheer - L+U
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Saturday, May 03, 2008 7:15 PM
Subject: Re: [EnergyPlus_Support] Window5 data file
Linda, et al.
Thanks. Looks like I'll have to do an experiment on the Unentered for the two cases with two zones...but for now:
I used explicit OtherZoneSurface definiitons in the current case, and there seems to be a problem with my window5 files. I created normal and reversed-layers window5 windows and specified them properly for the interior zone window and its facing object. But I'm getting very little Zone Diff Solar from Interior Windows compared to a similar model with its interior window/window_reversed pair defined as an E+ construction.
Any ideas? A few questions:
- glass has two surfaces, sometimes one of them has a loE coating. Shoudl this be reveresed also, as it needs to be to get proper performance? If it is reversed in Window5, doesn't that mean that it is actually a different material layer with different properties, and therefore it is no longer a reverse of the original window construction?
- Is there a way to see the report for interior windows, and therefore the performance numbers that E+ calcs? They don't show up in the Table report on Envelope Summary/Fenestration report, only exterior windows appear.
r3
----- Original Message -----
From: Linda Lawrie
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Saturday, May 03, 2008 7:15 AM
Subject: Re: [EnergyPlus_Support] Window5 data file
You use an UnenteredOtherZoneSurface as a shortcut to not having to
specify the adjacent zone surfaces. It does not fake anything,
merely calculates the proper position of the adjacent surface and
creates one plus adding the constructions (reversed layers) as needed.
The program generates the necessary geometry in a mirrored way from
the original and generates the proper constructions if necessary.
If you have an OtherZoneSurface with adjacent surfaces described,
then you shouldn't enter UnenteredOtherZoneSurface in the first zone
because you already have them. Then, you enter the proper surface
tags as the "outside environment"
As far as calculations there is no difference to entering the
"otherzonesurface" or using the shortcut. (ref: engineering manual
for details on the interzone heat transfer calculations".
Which has little or nothing to do with entering a Window5 data file
window in place for an interior window -- this works and the program
reverses the construction appropriately.
Linda
At 07:07 PM 5/2/2008, David Scheer - L+U wrote:
>Linda.
>
>The documentation is a little short on explanations about how
>UnenteredOtherZoneSurface is treated. Let me see if I assume correctly:
>
>If an 'adjacent' ( I understand that this is geometrically
>meaningless for the calculations) zone surface or subsurface is
>specified as OutsideFaceEnvironmentObject for a surface, I assume
>that the outside face condition of the surface in question includes
>adjacent object material energy balance, including radiative
>effects, etc, as well as zone temperature. Is this simplified to
>only include zone temperature if the other zone surface is
>'Unentered' and therefore generated as a proxy surface in the
>specified zone, not actual geometry in the adjacent zone? ie, is
>this condition of this proxy surface also calculated in the adjacent
>zone? And if so, what happens to the actual adjacent surface, if it
>is modeled in teh adjacent zone?
>
>If Unentered is specified, and real adjacent surfaces and
>subsurfaces exist in the adjacent zone, how should these be
>treated? Should these also have an Unentered object for their
>outside face environment, or can the actual adjacent surface be used?
>
>I assume that there is no concrete calculation of conservation of
>energy between two zones with adjacent surfaces, but that it works
>out pretty well due to the calculatino method. I assume that the
>outside face environment object is a way to simply define energy
>flows in/out of the surface through the outside face through the
>convection algorithm.
>
>With that in mind, for an internal window with potential solar
>gains, it would seem important that the position and orientation of
>the outside face environment object of the interior zone surface in
>relation to the exterior window is very important (even though only
>diffuse solar enters the interior zone, it is dependent on the
>directionality of solar through the exterior zone). That said, I
>can see how an Unentered surface would take care of the exterior
>zone surface outside face condition, but would not work well for the
>interior zone window surface.
>
>Afraid of faking out the software and losing energy.
>
>Phew!
>
>r3
>
>
> ----- Original Message -----
> From: Linda Lawrie
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Sent: Friday, May 02, 2008 11:41 AM
> Subject: Re: [EnergyPlus_Support] Window5 data file
>
>
> Don't forget... there is the UnenteredOtherZoneSurface that will take
> care of this instance if the base interior surface is used. Read
> about them in the Input Output Reference. EnergyPlus does the job of
> "reversing" the layers.
>
> Linda
>
> At 12:39 PM 5/2/2008, Rob Hitchcock wrote:
> >No warnings are generated for the case where internal windows (or other
> >surfaces) do not have reversed layer order for opposite sides of the
> >surface. However, layer orders should be reversed for interzone
> >windows, whether they are input directly in the IDF or by import from a
> >WINDOW5 data file. Of course if the window construction only consists
> >of a single layer, or if the layers are symmetrical, this does not matter.
> >
> >Rob
> >
> >coolshadow10a wrote:
> >
> > > Is it possible, and/or what should I look out for, to use a Window5
> > > data file construction for an internal window? Primarily, do I need
> > > to build another version of the window with the layers reversed for
> > > the facing subobject in the adjacent zone? The file runs with no
> > > warnings associated with the adjacency, just wondering if I'm being
> > > misled, and if solar through the interior window is still treated
> > > 'correctly'.
> > >
> > > r3
> > >
> > >
> >
> >
> >
> >
> >[Non-text portions of this message have been removed]
> >
> >
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> [Non-text portions of this message have been removed]
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>------------------------------------
>
>The primary EnergyPlus web site is found at:
>http://www.energyplus.gov
>
>The group web site is:
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>Attachments are not allowed -- please post any files to the
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>Yahoo! Groups Links
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