Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Changing the coefficient of infiltration in Open Studio

asked 2018-10-17 13:35:13 -0600

AS1 gravatar image

updated 2018-10-18 08:15:19 -0600

I am trying to work on a single family slab foundation, vintage – 1960s (created in ResStock) model in open studio. I want to change the airflow changes/hour (ACH 50) for the model. From the IDF file I know that in order to change the ACH, I need to change the coefficient for infiltration. Is there any way to do this? I know I may be able to alter the Eplus portion of the measure in order to do this - but is there any other way to manually input the coefficient in Open Studio? Or any other advice to do this?

By coefficient I mean the c value in the IDF file. Below is an extract of the exported IDF file. I only know the c value (Program line 10). How do I modify that in Open studio? I do not have the infiltration in terms of cfm/sqft etc that can be input from the space type tab in OS.

image description

edit retag flag offensive close merge delete


To clarify: by "coefficient" are you referencing an input such as CFM/SQFT of exterior wall, CFM/SQFT, etc...? If so I have a straightforward response. This can definitely be directly altered in OS.

I'm not sure what measure it is that you are speaking of when you refer to "alter[ing] the Eplus portion of the measure."

jbatt gravatar image jbatt  ( 2018-10-17 16:05:07 -0600 )edit

I have modified my question above to try to answer your question.

AS1 gravatar image AS1  ( 2018-10-18 08:15:57 -0600 )edit

Do you know what the coefficient represents? Is it unit-less?

And if I understand correctly, you have known values for this coefficient, but not for anything that will allow you to directly edit infiltration ACH or CFM/SQFT (?).

jbatt gravatar image jbatt  ( 2018-10-18 08:37:38 -0600 )edit

I am not sure what the coefficient represents exactly. It does seem to be unit less. Yes, I have a value I want to change for the coefficient. But I also do know the ACH 50 value. But not in terms of cfm/sqft etc. Can I directly use the ACH 50 value anywhere?

AS1 gravatar image AS1  ( 2018-10-18 08:45:30 -0600 )edit

So if you look at the screenshot I sent, you can directly edit ACH, but I believe that this is "standard" infiltration. I'm not sure how this compares to ACH at a 50pa pressure difference, but my instinct would be that it is lower, maybe much lower (I'll leave that to someone else on the forum). If the input for ACH is not a close approximation of ACH50, I'm sure you can lookup some kind of conversion factor.

jbatt gravatar image jbatt  ( 2018-10-18 09:03:48 -0600 )edit

1 Answer

Sort by » oldest newest most voted

answered 2018-10-17 16:17:01 -0600

jbatt gravatar image

updated 2018-10-18 10:03:57 -0600

Pending your response to my above comment:

Infiltration in the OS interface is defined in the Spacetypes tab. In order to edit the infiltration seen by each zone, click on the box that is highlighted in yellow and the edit window on the right-hand side will appear. Here you can enter a coefficient for infiltration using any of the metrics shown below (as you can see, in my model I had entered a value for CFM/SQFT of exterior surface area). image description

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops

Question Tools

1 follower


Asked: 2018-10-17 13:35:13 -0600

Seen: 298 times

Last updated: Oct 18 '18