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Fan Assists Night Ventilation

asked 2015-11-23 18:14:04 -0500

Phil's avatar

updated 2017-08-05 13:07:51 -0500


I tried to use the Fan Assists Night Ventilation Measure for a very simplified model. When I added one more space to my model, with an obvious air trace, the simulation failed. Unfortunately I cannot upload my .osm files. What do you think could be wrong in my model? There is just one possible air trace and both windows are operable.

Thank you

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answered 2015-11-23 23:35:23 -0500

What kind of error are you seeing, and what version of OpenStudio are you using? There is an issue filed and fixed for our next installer that affected zone ventilation objects on un-conditioned zones, but the measure has a work around for that (add's a dummy exhaust object).

This measure was made to demonstrate zone mixing and zone ventilation objects added to the OpenStudio API in OpenStudio 1.9.0, and for use with a class doing a simple night ventilation analysis. Here is a link to PDF that gives an overview of how to use the measure.

The basic idea of the measure is to use operable exterior windows and operable interior windows and air walls to define a zone ventilation object followed by a string of zone mixing objects. Below are a few screenshots from the PDF mentioned above.

image description
View of Model in SketchUp Plugin

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Diagram of Intended Outcome of Measure

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Thank you for your fast response.

I used the guide you suggested above. Then I added more and more spaces to the model to see if anything unwanted happens. I wanted to try this before I am changing a lot of interior walls in my complex model. At one point, after adding one more space the simulation failed without any error messages. I am using OS Version 1.9.0, could that be a problem? Is there a way to upload the .osm files so you could have a look on it?


Phil's avatar Phil  ( 2015-11-24 10:07:24 -0500 )edit

You can email it to and I can take a look at it, but may take some time. See if this webpage helps you find out what the error is. If you find out, post back here.

David Goldwasser's avatar David Goldwasser  ( 2015-11-24 10:18:19 -0500 )edit

Thanks, I got the file, and I can reproduce your issue. Your model failed before the measure was added because ThermalZone 18 doesn't have an area, because the floor drawn as a roof. When I fixed that EnergyPlus ran but the measure still fails and in fact gets caught in a loop (which is why you don't see an error). The issue happens when the path moves more than one space horizontally before moving Up a shaft or ending. I'll try to fix this and get an updated measure on BCL, but will probably be sometime next week.

David Goldwasser's avatar David Goldwasser  ( 2015-11-25 13:25:11 -0500 )edit

Thank you very much, I really appreciate your support.

Phil's avatar Phil  ( 2015-11-25 20:07:43 -0500 )edit

Updated measure with bug fix is on BCL.. I did notice your model has a large window in a wide room, that then goes down a long corridor to get to the atrium. While this measure may show a certain cfm going, that doesn't mean it would really work. You may want to review the model and reduce the operable window area.

David Goldwasser's avatar David Goldwasser  ( 2015-12-08 02:20:16 -0500 )edit

answered 2015-12-17 17:32:31 -0500

Phil's avatar

I applied the measure to my model and everything works now. Thank you again for your help and updating the measure.

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Asked: 2015-11-23 18:14:04 -0500

Seen: 432 times

Last updated: Dec 17 '15