Annual OA?

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Hi there, me again!

Is there a way to compute the total outdoor air volume supplied to a building over the course of the year if only the SIM file is available?

Thanks in advance!
Mark Hallman.

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Mark Hallman's picture
Joined: 2016-02-03
Reputation: 0

Only in a constant volume fixed fraction AHU would that be possible.

Otherwise you need hourly data as VAV and an economizer would change the volume hourly.

Sorry I don't have a more clever answer.


Fred Betz PhD., LEED AP (r)BD+C
Senior Sustainable
Design Consultant

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Fred Betz's picture
Joined: 2011-09-30
Reputation: 0

I am going to give this a try, although I have never done this before.

You could do an excel calculation of when the economizer would be used and
how much OA it would give based on OA temp, return temp (from thermostat
schedule), and assumption on supply temp (I am not sure if this is
available somewhere in sim file), and system/fan schedule. Rest of the time
you can assume min OA from the SS-A reports.

This might give you a ball park number, unless I am missing some important
Good luck!

R B's picture
Joined: 2011-09-30
Reputation: 4

If you have the model, and not just the SIM file, you can determine total OA by creating hourly reports:
Select the following options under the ?HVAC System? variable type:
?Ratio of outside air to total supply air?
?Total system supply air flow rate?
After simulating, click the ?Hourly Reports? button in the D2SimViewer tool bar.
Multiply hourly OA% times system cfm for each hour and sum to get total annual OA cfm for that system.
Repeat for each system.

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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Bill Bishop's picture
Joined: 2012-02-25
Reputation: 7

Hello Mark,
With only the SIM file it would be difficult to calculate the total
outdoor air volume supplied. There is the economizer issue noted by
others. In addition, if the fans cycle on during unoccupied hours, you
would need to know if the minimum outdoor air schedule was programmed
to not allow outdoor air when the fans cycle on. Without the input
file, I don't think you could really be sure of any estimate
calculated from only the sim file.

Chris Jones
Toronto Island

Quoting Mark Hallman :


Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3

Chris Jones's picture
Joined: 2011-09-30
Reputation: 0