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# I got different values for Window to Wall Ratio (WWR) of the same building geometry using two different approaches ?

I calculated WWR using the following methods ( for which i got different values) 1) simulated the model in open studio and and the results of the simulation gave window to wall ratio values ( which appears very low) 2) i calculated the area of the window and wall surface( selecting the surface and sketchup tells me area) and calculated the window to wall ratio manually ( the values make sense but is nearly 3 times the values given by simulation (step 1))

Please help and tell me which is the simulation of model is giving me a values of ~9% for 8 storey campus university dorm. Manually the WWR comes ~35% which makes sense.

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For scenario '1' did you use the SketchUp plugin or did you run a measure. Also did you apply it to the entire building or just specific facades. For scenario '2' did you select SketchUp surfaces that already had windows in them? Also does you model have any plenum or attic zones?

( 2016-11-23 17:40:36 -0500 )edit

For Scenario 1: I used the Open studio tool/plugin which simulated the sketch up model. I did it floor wise. I deleted all floors but one and assigned the whole floor to one thermal zone and then simulated model to get the WWR in the open studio results section. I did this all floors one by one.

For Scenario 2 : Yes I calculated the surface area of the building model that had already window in them . I calculated it as WWR = window area/(window +wall area). Yes, the building has plenum in it.

Kindly help

( 2016-11-25 23:53:11 -0500 )edit

Does your model have matched internal surfaces, so that the boundary condition of internal surfaces is 'Surface', instead of 'Outdoors'?

( 2016-11-27 14:20:42 -0500 )edit

Thanks

( 2016-11-28 09:15:42 -0500 )edit
1

1. Per @Eric Ringold's question, if your one zone per floor is made up of multiple spaces assigned to the same zone but not surface matched, you could have a lot of exterior windows.
2. The WWR user script and WWR measure don't currently know to ignore plenum zones (make sure you are not adding windows to the plenum.
3. How are you manually calculating the surface area of the building with windows? If you select a base surface in SketchUp it doesn't include the area of the window.
4. Are you hand drawing windows in Scenario 2.
( 2016-11-28 10:46:56 -0500 )edit

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I guess the problem was resolved. According to @David Goldwasser and @Eric Ringold's suggestion, I matched the interior surfaces (Surface Matching) and then found the WWR . Now i get similar values of WWR using both approaches. I hope the problem is resolved. Thanks. i will keep in touch for further questions and from next time i will upload screenshots.

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