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# The surface has an edge that is either not an edge on another surface or is an edge on three or more surfaces

Can anyone help me understand why I'm encountering these warnings?

I defined two zones, one within the another one.

Program Version,EnergyPlus, Version 9.2.0-921312fa1d, YMD=2024.02.04 20:05,
** Warning ** CalculateZoneVolume: The Zone="OUTER ZONE" is not fully enclosed. To be fully enclosed, each edge of a surface must also be an edge on one other surface.
**   ~~~   **   The zone volume was calculated using the opposite wall area times the distance between them method
**   ~~~   **   The surface    "iz-INNERZONE WALL 1" has an edge that is either not an edge on another surface or is an edge on three or more surfaces:
**   ~~~   **     Vertex start { 1.0000, 1.0000, 0.0000}
**   ~~~   **     Vertex end   { 1.0000, 4.5000, 0.0000}
**   ~~~   **   The surface    "iz-INNERZONE WALL 2" has an edge that is either not an edge on another surface or is an edge on three or more surfaces:
**   ~~~   **     Vertex start { 5.0000, 1.0000, 0.0000}
**   ~~~   **     Vertex end   { 1.0000, 1.0000, 0.0000}
**   ~~~   **   The surface    "iz-INNERZONE WALL 3" has an edge that is either not an edge on another surface or is an edge on three or more surfaces:
**   ~~~   **     Vertex start { 5.0000, 4.5000, 0.0000}
**   ~~~   **     Vertex end   { 5.0000, 1.0000, 0.0000}
**   ~~~   **   The surface    "iz-INNERZONE WALL 4" has an edge that is either not an edge on another surface or is an edge on three or more surfaces:
**   ~~~   **     Vertex start { 1.0000, 4.5000, 0.0000}
**   ~~~   **     Vertex end   { 5.0000, 4.5000, 0.0000}


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( 2024-02-05 09:32:40 -0600 )edit

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The edge (along Z=0) of each "INNERZONE" wall should ideally be paired with at least another edge (usually of another surface), defined in the opposite direction (eg if zone volumes are to be autocalculated). I suspect that the floor of the "OUTER ZONE" is simply a 4-vertex rectangle (6m x 6m)?

The "OUTER ZONE" floor isn't really a 4-sided 6m x 6m convex polygon - it's a 6m x 6m 2D torus, i.e. a flat 4-sided "donut". EnergyPlus doesn't like cutouts (i.e. "donut holes"). You can try delineating the 3.5m x 4m cutout with a double leader line (as described here) to autocalculate eg floor area and zone volume, but that still leaves you with a non-convex "OUTER ZONE" (if that's an issue).

There are plenty of EnergyPlus models with non-convex zones, including some of the US DOE Commercial Prototype models. It's up to you to determine how critical is zone convexity in your analysis. If so, the recommended solution would then be to split the "OUTER ZONE" into 5 convex zones (separated between each other with Air Boundaries): 4 perimeter zones around the "INNERZONE" walls + one above the "INNERZONE" roof/ceiling. That may be taking things too far in your case.

Based on a recently shared model of yours, and that you're likely after a +/- guarded hotbox setup, I suggest simplifying the geometry and related E+ parameters for starters. For instance, manually calculate/set the "OUTER ZONE" volume, height and floor area, rather than rely on autocalculate. Also, setting the Solar Distribution parameter to "FullInteriorAndExterior" seems odd in your case - try something more basic. All surfaces could be set to NoSun/NoWind, etc. If this is for graduate work, I'd document the final parameter selection (based on a modest set of sensitivity runs) - you'd want to reassure readers of the final parameter selection, and that remaining E+ warnings are considered benign in your case. I'd nonetheless avoid overlapping floors - either with 4 separate "OUTER ZONE" perimeter floors, or the leader line trick. Hope this helps.

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Thank you, @Denis Bourgeois, for your clarification.

Is there a more straightforward method?

I want to simulate an indoor walk-in freezer in the inner zone with constant boundary conditions, unaffected by outdoor conditions. That's why I've defined two zones. Any alternative recommendations?

( 2024-02-05 10:56:36 -0600 )edit

@Zakaria, I edited my initial suggestions, in an attempt to answer your follow-up questions. Hope this helps. Best of luck.

( 2024-02-05 14:49:21 -0600 )edit