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Re: [EnergyPlus_Support] Modelling

1.  No.  With MinimalShadowing "there is no exterior shadowing except from 
window and door reveals."  See Input Output Reference, p. 11, pdf (p. 44) for 
more details.

2a.  For thermal absorptance 0.9 is reasonable for most materials except 
selective surfaces and shiny metals.  For visible absorptance, if you have no 
other data, using the solar absorptance is quite reasonable.  The "solar" range 
of wavelenghts in EnergyPlus includes the "visible" range, and the visible 
range is a large fraction of the solar flux.

2b.  For opaque surfaces, emissivity and absorptance are equal.  If you have a 
thermal emissivity value, it can be entered directly for absorptance:thermal.

3a&b.  For glass, IR transmittance is zero - IR does not pass through glass or 
most common window materials.  Look at the predefined window glass objects in 
WindowGlassMaterials.idf the DataSets folder.  This may help you understand the 
various properties more clearly.  

4.  Shade materials properties are only for the shade.  Then the window is 
calculated using the shade properties along with the other window material 
layer properties.

Mike


On 23 Aug 2005, at 21:42, Clarice Bleil de Souza wrote:

> Hi everybody,
> 
> I'd like to ask the following questions about E+ modelling:
> 
> 1) Overshadowing:
> Does Energy Plus minimal shadowing solar distribution accounts for interzonal
> shading? How about self-shading? Are both only accounted in the full exterior or
> in the minimal shading as well?
> 
> 2) Materials:
> 2.a - I only have data for solar absorptivity of the opaque materials can I
> assign this same value for thermal absorptivity and visible absorptivity or
> should I use the defaults 0.9 and 0.7 respectively? 2.b - How about emissivity
> values? How do I specify emissivity values for opaque materials?
> 
> 3) Windows:
> 3.a - What exactly is the IR transmittance? I can get values for the solar
> transmittance and the visisble transmittance in ASHRAE Handbooks of fundamentals
> pg. 30.26 to 30.33, but I cannot find values for the IR transmittance, would
> this be similar to the U-value but without the air layers?  Where can I get this
> values? Can I use the same value I used for the solar transmittance to simplify?
> 3.b - Can the values assigned to visible reflectance be the same as those
> assigned for solar reflectance, as I do not have any other option for them?
> 
> 4) Shading:
> Do the transmittance, reflectance and emissivity values refer only to the shade
> or to the composition window + shade? 
> 
> Once again thank you in advance for the help and attention and hope hearing from
> you soon,
> 
> Best regards,
> 
> Clarice
> 
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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