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Infiltration Rates Not Responding As Expected

asked 2016-10-17 15:22:11 -0500

Michael Pelton's avatar

updated 2017-04-16 11:08:08 -0500

I have setup OS:SpaceInfiltration:DesignFlowRate in a model as follows:

Schedule = Fractional (Value=1 for all times) Design Flow Rate Calculation Method = Flow/ExteriorWallArea Flow per Exterior Surface Area = 0.0025 Constant Term Coefficient = 1 Other 3 Coefficients = 0

My understanding (after reading the Input/Output Reference) is that this should result in a constant flow of infiltration air (for all times) at the volume flow rate specified. However, when I review results, the infiltration rates in the model appear to vary significantly. Any ideas about what is going on?

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answered 2016-10-17 16:06:32 -0500

Michael Pelton's avatar

It looks like this might have something to do with differences in air density. The infiltration design flow rates are entered in volumetric flow units (m3/s) - but the hourly reports are showing fluctuations in mass flow units... When the OA temperature is low (i.e. the air is dense) the mass flow rates seem to be higher (and vice versa)...

However, the OpenStudio report lists an Average ACH and a Minimum ACH (both volumetric) and they are very different (by an order of magnitude for most zones)... Still can't explain this.

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Asked: 2016-10-17 15:22:11 -0500

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Last updated: Oct 18 '16