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component load summary meaning

asked 2016-03-03 21:39:32 -0500

ngkhanh gravatar image

updated 2016-04-02 13:08:03 -0500

When i see the zone component load summary, i see that
image description
Where i can get meanings of each component? The zone ventilation is for natural ventilation ? and exterior wall is confused vs Fenestration Conduction and solar ?

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answered 2016-03-04 11:45:25 -0500

updated 2016-03-04 12:09:37 -0500

For more info about Zone Component Load Summary tables, check this I/O Document article for general topics and check this Engineering Reference article for calculation assumptions and methods. Basically, this table is showing all of the heat transfer components that contribute to heat gains and losses in one zone. All of these heat transfer components eventually impact sizing calculations for HVAC equipment.

To answer your specific questions:

  • According to documentation for the ZoneVentilation:DesignFlowRate object,

    Ventilation is the purposeful flow of air from the outdoor environment directly into a    thermal zone in order to provide some amount of non-mechanical cooling.

This object can model the ventilation to occur with or without fans (mechanical ventilation or natural ventilation). Natural ventilation is different from Infiltration. According to the ZoneInfiltration:DesignFlowRate object,

Infiltration is the unintended flow of air from the outdoor environment directly into a      thermal zone. Infiltration is generally caused by the opening and closing of exterior doors, cracks around windows, and even in very small amounts through building elements.

Therefore, the Infiltration row in the table above is for outside air entering through cracks and openings. If you modeled outside air being brought into the zone on purpose using a Ventilation object, then that will appear in the Zone Ventilation row in the table above.

  • Exterior Wall is for the opaque exterior wall surfaces, while Fenestration Conduction and Fenestration Solar are for the window aka fenestration sub-surfaces and their conduction heat transfer and transmitted solar gains, respectively.
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  • Thank you a lot for explanation. i have question about formula for People load - in my example, people schedule people activity is 120 w/person and nominal people counts 3.25 and number of people schedule = 1 (120x3.25x1 = 390W) so how to get 371 W total load with those input ?
  • in E+ documentation link, there are only names of internal gain types of each load type in table, not how to get them - where are their formulas ?
ngkhanh gravatar imagengkhanh ( 2016-03-05 09:12:37 -0500 )edit

@ngkhanh sorry for the delayed response. I would check the people occupancy schedule to see if it's 1.0 on SummerDesignDay and WinterDesignDay. My guess is that it's set to 0.95, since 371 W / 390 W ~= 95%. As for load type formulas, I can't find them in either document easily. For items like this, where you want EnergyPlus to address something that isn't a bug, there's a User Feedback website. I've made a new topic about this issue at

Aaron Boranian gravatar imageAaron Boranian ( 2016-03-08 13:58:53 -0500 )edit

Thank for your reply. I checked my model but summer design schedule = 1 all hours in my model. Please let me know about the code source where i can see about calculation step for zone load component. thank

ngkhanh gravatar imagengkhanh ( 2016-03-08 19:06:00 -0500 )edit

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Asked: 2016-03-03 21:39:32 -0500

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Last updated: Mar 04 '16