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After successfully coupling CONTAM and Energy+, CONTAM does not calculate design flow rate based on design day information. ZoneInfiltration:DesignFlowRate is zero.

asked 2018-07-16 23:27:40 -0500

Siv gravatar image

updated 2019-03-05 06:53:54 -0500

dhollman gravatar image

After successfully coupling CONTAM and Energy+, the simulation dynamically calculates the infiltration and temperature. However, the infiltration loads in Energy+ output file is still zero because CONTAM exported IDF contains a design flow rate of zero in ZoneInfiltration:DesignFlowRate. Does CONTAM not calculate the design flow rate for infiltration based on Design day information ?

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answered 2018-07-17 06:28:35 -0500

Stuart Dols gravatar image

updated 2018-07-17 10:06:05 -0500

I'm assuming you've used the Contam3DExporter to generate your IDF file. As indicated in the CONTAM documentation (quoted below), you must modify this IDF file to incorporate the energy related components of the building. This includes the design loads and other items that the CONTAM paradigm does not incorporate, e.g., "Design day information".

The Zone Infiltration is calculated by CONTAM during the co-simulation and will override any values set for the ZoneInfiltration:DesignFlowRate object.

EnergyPlus-CONTAM Coupling Process

Modify IDF File The IDF file generated by CONTAM3DExport contains the building geometry, surface materials and constructions, air loops, exhaust fans and partial external interface objects as described above. However, the file will not include the HVAC components associated with the generation or removal of energy, e.g., heating/cooling coils, internal gains, and thermostats. The IDF file can now be edited using the IDF Editor or other text-based editor to add the desired HVAC system components. The IDF file can also be viewed and edited using tools such as SketchUp with the OpenStudio plug-in [Gugliemetti 2011, NREL 2015]. This is useful to modify the rectangular elements that are created by CONTAM3DExport, for example to modify roofs to have sloped surfaces and to add shading components to the building.


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I have incorporated all the design HVAC Components, altered the node names and made all the necessary changes. My doubt is that, the CONTAM populated ZoneInfiltration:DesignFlowrate object has a design flow rate value of 0. If I should give it a non zero value, based on what should I do that ? How should I choose the design infiltration flow rate ? Because, running it with a value 0 calculates infiltration but the infiltration load becomes zero.

Thank you for your response in advance.

Siv gravatar image Siv  ( 2018-07-17 06:36:38 -0500 )edit

I'm not sure how you are determining the "infiltration load becomes zero". E+ should calculate and report the infiltration loads based on the infiltration calculated by CONTAM.

As best I understand it (and I hope any E+ gurus out there will correct me if I'm wrong), you can set the ZoneInfiltration:DesignFlowRate value to be used during sizing.

E+/CONTAM co-simulation is not used during the sizing calculations. However, you can use CONTAM alone, e.g., to run simulated Building Pressurization Tests to determine air leakage rates to be used to populate ZoneInfiltration:DesignFlowRate.

Stuart Dols gravatar image Stuart Dols  ( 2018-07-17 11:01:28 -0500 )edit


Since Infiltration is given by Idesign(A + B(DT) + CW + DW*W) and since the CONTAM generated IDF automatically generates a design flow rate value of 0 in ZoneInfiltration:DesignFlowRate the infiltration loads I obtain using ZoneLoadComponentSummary is always zero. However, when I check the zone infiltration mass flow rates using Output:Variables object, I am able to determine the infiltration values. My doubt is, why this value is not used to determine the loads ?

And why should E+/CONTAM not be used for sizing calculations ?

Siv gravatar image Siv  ( 2018-07-17 12:46:41 -0500 )edit

As I understand it, the ZoneLoadComponentSummary report is based on the Sizing conditions and not the simulation RunPeriod. You should be able to tell this from the Time of Peak Load provided in the report. It should match the date provided for your SizingPeriod. Crank up the infiltration DesignFlowRate to force infiltration to be a significant portion of the load, e.g., 10 ach, and you should see a value in this report.

I think you're better off looking at the Sensible Heat Gain Summary report for simulation RunPeriod results.

Sizing is based on design conditions SizingPeriod:xxx.

Stuart Dols gravatar image Stuart Dols  ( 2018-07-17 14:14:24 -0500 )edit

Thank you for your patience.

Of course, when I crank up the design flow rate I am able to see the infiltration load. But, I did not know that ZoneLoadComponentSummary is based on SizingPeriod. Finally,

  • Is it right to say that E+/CONTAM coupling is used to determine infiltration using CONTAM's infiltration calculation methodology and temperatures using E+ ?

  • Which methodology is more accurate for determining infiltrations? Giving effective leakage areas to E+ without coupling or E+/CONTAM coupling ?

Siv gravatar image Siv  ( 2018-07-17 23:12:37 -0500 )edit

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Asked: 2018-07-16 23:27:40 -0500

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Last updated: Jul 17 '18