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Natural ventilation result equal to zero

asked 2021-02-24 12:00:32 -0500

crisrossatto's avatar

updated 2021-02-24 12:35:28 -0500

I am modeling a project that is totally naturally ventilated, in the results of air changes per hour (ACH), some hours have zero values. Looking at the weather file that I use, in some points the values for wind speed are zero and in those same points I have the result with zero value for air changes per hour (ACH). The results seem to be in compliance, but in the project there is an exhaust system that works passively and causes exhaustion even when the wind speed values are equal to zero. How can I represent this element of exhaustion that makes air changes happen even when the weather file says that the wind speed is equal to zero (without energy consumption)?

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@crisrossatto please add a tag for the simulation tool you are using so that others can provide better help.

Aaron Boranian's avatar Aaron Boranian  ( 2021-02-24 12:04:49 -0500 )edit

Added. I am using Energy Plus 8.6

crisrossatto's avatar crisrossatto  ( 2021-02-24 12:13:42 -0500 )edit

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answered 2021-02-25 16:49:15 -0500

Sounds like you need to model an exhaust only ventilation system. You can add a zone exhaust fan, and set it to run when air speed is zero with a Schedule:File object that you calculate from the weather file, or alternatively, if you want to do this for several buildings / weather files, write some EMS code to toggle the fan availability based on an outdoor air speed sensor.

For natural ventilation if your project is more than one zone (airflow happens across multiple zones), you'll need to use the Airflow Model Network objects, which are documented here

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Thanks for the answer! I am already using AirflowNetwork objects for natural ventilation. To use Fan: ZoneExhaust do I need to link it with the AirflowNetwork:Distribution:Component:Fan object? Will adding a fan to the zone generate energy consumption?

crisrossatto's avatar crisrossatto  ( 2021-02-26 06:08:33 -0500 )edit

yes, exactly, you need to link the objects. And yes, fans do use energy, so you will see that from your fan.

mdahlhausen's avatar mdahlhausen  ( 2021-02-26 13:08:37 -0500 )edit

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Asked: 2021-02-24 12:00:32 -0500

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Last updated: Feb 25 '21