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What is the correct way to implement infiltration?

asked 2021-01-07 05:51:01 -0600

Pieter_Proot gravatar image

updated 2021-01-07 05:55:53 -0600

I have some struggles with implementing infiltration in my OpenStudio model. If I understand it well, is infiltration the flow of air from the outdoor environment directly into a thermal zone? So this can be caused by opening and closing doors, some cracks around windows, .. ? Does the airflow caused by opening the windows also belong to the infiltration input parameter? During the summer period here in Belgium, a lot of residents open some of their windows at night or during the evening to enhance the effect of free (night)cooling. I was also wondering if there are any default values that represents a good estimate of the airflow caused by infiltration that I can use for the design flow rate ?

In my model I have implemented a mechanical ventilation, but I got the advice to also implement infiltration. I found two ways to implement infiltration into my model. Is there a difference between the two and which one I use best?

First one: space types < General < space infiltration design flow rates

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Second one: Spaces < Airflow < space infiltration design flow rates

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answered 2021-01-07 10:18:08 -0600

Infiltration is outdoor air UNintentionally entering the building through cracks, leaks, etc. while the building envelope is "sealed" (doors closed, windows closed, etc.). The window opening events would be an example of natural ventilation -- outdoor air intentionally entering the building for some purpose (free cooling, e.g.). You can read this post for more details on modeling natural ventilation in OpenStudio.

The two approaches of assigning infiltration from your screenshots (Space Type input vs. Space input) are essentially the same, but the space type approach will likely be easier and faster. You can read this post for more information on that topic. This post also discusses using blower door results at 50 Pa and converting that to a natural infiltration rate.

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Asked: 2021-01-07 05:51:01 -0600

Seen: 102 times

Last updated: Jan 12