Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page

# OS distributed analysis Window to Wall Ratio

In a Distributed Analysis (when I have plenums), is it possible to have the existing "set-window-to-wall-ratio" measure disregard the exterior surfaces of the plenums if included in the Analysis Spreadsheet?

The building won't use plenums for return air actually, they are just there currently in the Revit model and will likely remain. Just curious if the measure as it stands can or can't be pinpoint-directed to surfaces (or, groups of surfaces with a common name tag for instance) in a Distributed Analysis, or if cardinal direction is the only distinguishing characteristic to apply.

edit retag close merge delete

Sort by ยป oldest newest most voted

The original Window to Wall Ratio measure does just look at surface orientation along with surface type, but you can really filter any way you want to. This could be based on surface, space, building story, or space type name, or some other attribute of one of those objects.

When we made the AEDG measures we had added the plenum object to OpenStudio so those fenestration measures do skip plenums, but it figures out the plenum by a user specified standards space type (more reliable then just using the name of a space type). The office and school have different logic on the size of the window based on how the guides were written. This includes a customized version of what is north, south, east, west vs. the way our basic measure works (which splits at the 45 degrees).

AEDG Small to Medium Office - Fenestration and Daylighting Controls

AEDG K12 - Fenestration and Daylighting Controls

Below I pasted in a block of code from our basic measure. It loops through each surafces without regard to which space they come from, but it could very easily be changed to first loop through spaces or even space types, and then for each space it could loop through surfaces.

You could add any kind of logic to skip a space type such as what is below

next if not space_type.name.to_s.include? "plenum"


There is an OpenStudio option to check of a zone is a plenum, but that would only be useful after the HVAC system has been added, which typically would be after fenestration is created. Any sort of name or space type filter requires the user to take some action to identify spaces that they later intend to use as plenums. One alternate solution would be to keep the logic similar to what is in the main block below, but check each surface to see that it is higher than a target test height. This could be a hard coded height or could be a user argument. This would work without much prior thought from the modeler, other than what would be typical for a plenum.

 #data for final condition wwr
surfaces = model.getSurfaces
surfaces.each do |s|
next if not s.surfaceType == "Wall"
next if not s.outsideBoundaryCondition == "Outdoors"
if s.space.empty?
runner.registerWarning("#{s.name} doesn't have a parent space and won't be included in the measure reporting or modifications.")
next
end

# get the absoluteAzimuth for the surface so we can categorize it
absoluteAzimuth =  OpenStudio::convert(s.azimuth,"rad","deg").get + s.space.get.directionofRelativeNorth + model.getBuilding.northAxis
until absoluteAzimuth < 360.0
absoluteAzimuth = absoluteAzimuth - 360.0
end

next if not (absoluteAzimuth >= 315.0 or absoluteAzimuth < 45.0)
next if not (absoluteAzimuth >= 45.0 and absoluteAzimuth < 135.0)
next if not (absoluteAzimuth >= 135.0 and absoluteAzimuth < 225.0)
next if not (absoluteAzimuth >= 225.0 and absoluteAzimuth < 315.0)
else
runner.registerError("Unexpected value of facade ...
more

@Neal Kruis I noticed that when I look at my answer in initial view the ruby has syntax highlighting, but when I click "more" it is just raw text, and much harder to read. Is there a way to update the site to keep the syntax highlighting on the full view?

( 2014-12-09 15:21:46 -0500 )edit

@Kent Beason, I wanted to point you to this other post that talks about some of the issues you can hit making plenum zones. Specifically if you end up with a very large number of surfaces in that zone (due to complexity of zones above and below it) it can really slow down your simulation. Not surface matching/intersecting the plenum floor/ceiling surface can avoid this issue.

( 2014-12-09 15:25:32 -0500 )edit

@David Goldwasser I'll look into improving syntax highlighting, and add this to the bug list.

( 2014-12-12 09:47:15 -0500 )edit