WWR calculation excludes Basement Wall Area

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The WWR calculation reported in the AnalysisResults.xml and Envelope.csv do not 
account for the Basement Wall area. WWR reported in the EPlus html report 
includes basement walls. ACM and the Standards defines "WINDOW WALL RATIO is 
the ratio of the window area to the gross exterior wall area". In the Standards 
definition of Gross Wall area does not exclude the below grade walls. The 
exclusion of basement walls in WWR calculation may get problematic in instances 
where a portion or a particular orientation of the below grade floor has 
windows on walls exposed to ambient conditions. We had some internal discussion 
on this topic and feel that the team should come to a common agreement 
regarding definition for WWR.

Original issue reported on code.google.com by chitra.nbr on 21 Mar 2014 at 12:25

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I don't believe that the intent of the standard is to include below grade walls 
in the calculation of WWR.  For example, say you have a building with 1 story 
above grade and a basement, with the basement and above grade walls of equal 
height.  The proposed design has windows in the above grade floor which have a 
WWR of 80% of the above grade walls.  If the WWR for the standard includes the 
below grade wall, windows in the baseline would not be reduced at all, since 
the WWR when the basement wall is included is 40%.  That seems to me to be 
pretty obviously not the intent.  

Original comment by rhedr...@archenergy.com on 21 Mar 2014 at 12:32

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Also, were not excluding basement walls from the calculation of WWR, but below 
grade walls.  If there is a basement with window wells, the portion of the wall 
with windows that is exposed to the outdoors should be included in the WWR 
calculation.  This exposed portion of the wall would need to be identified in 
Sketchup as a separate surface from the adjoining wall with the outside 
boundary condition set to ground.  

Original comment by rhedr...@archenergy.com on 21 Mar 2014 at 12:38

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Rogers comment #2 sounds like a good approach to me. I suggest including the 
procedure for modeling such walls in Sketchup in the FAQ page and some language 
in the ACM to clarify the WWR calculation for Basement walls with windows 
exposed to ambient conditions. 

Original comment by chitra.nbr on 26 Mar 2014 at 7:48

• Changed state: Resolved

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Original comment by cnambiar@archenergy.com on 20 May 2014 at 9:19

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Changing owner to John.  Just need ACM language to close this issue.  

Original comment by rhedr...@archenergy.com on 8 Aug 2014 at 3:54

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Fenestration Geometry:

Note that "basement wall" is not defined in the ACM RM, is not formally defined 
inthe Standards (although it is mentioned a couple of times), and I do not wish 
to define it here.

Adjusting definition in Standard Design:

"The window wall ratio is the total fenestration area (including framing) 
divided by the gross exterior wall area (excluding wall area that is below 
grade)."

I think Roger's example of a window well is a good one; I would be ok NOT 
including this window area in the WWR calculation (probably low direct solar 
gains), but don't have a strong preference either way.  Is a window well and 
associated wall for a ground/basement level that has an exterior stairwell, is 
below sidewalk grade level but has an exterior window considered "below grade"?

If the above language is insufficient

Original comment by johnaren...@gmail.com on 15 Aug 2014 at 4:10

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Technically, the walls we want to exclude are underground walls (UndgrWall).  
The window well is below grade, but we would want to include the wall that 
window is on.  In SDD the walls to include are all ExtWalls, excluding 
UndgrWalls.  

I recommend revising to make the parenthetical, "(excluding underground 
walls)."  By underground walls I mean those that are in contact with the 
ground, if you think underground walls is not clear enough.  

Original comment by rhedr...@archenergy.com on 15 Aug 2014 at 4:51

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Technically, the walls we want to exclude are underground walls (UndgrWall).  
The window well is below grade, but we would want to include the wall that 
window is on.  In SDD the walls to include are all ExtWalls, excluding 
UndgrWalls.  

I recommend revising to make the parenthetical, "(excluding underground 
walls)."  By underground walls I mean those that are in contact with the 
ground, if you think underground walls is not clear enough.  

Original comment by rhedr...@archenergy.com on 15 Aug 2014 at 5:18

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Ok, sounds good.

How about adding something to the effect of:

"Any below grade exterior walls and associated windows that are exposed to 
outdoor ambient conditions shall be included in the WWR calculation."

And I think we discussed before, but what about sites on a graded surface, 
where a story might be partially below ground and partially above ground?

Original comment by JohnJArent on 15 Aug 2014 at 5:24

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I think your wording covers it.  The building story doesn't come into it - wall 
areas exposed to ambient air are included, those facing ground are not.

Original comment by rhedr...@archenergy.com on 15 Aug 2014 at 5:27

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Original comment by cnambiar@archenergy.com on 14 Oct 2014 at 7:08

• Changed state: DoneVerified
• Added labels: Type-Other
• Removed labels: Type-Defect