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Doubt on how to "fix" a non-convex zone in E+

asked 2024-02-05 08:24:32 -0500

paula's avatar

updated 2024-02-12 07:49:33 -0500


I'm using E+ to help me design a country house. The house has a roof of 2.5m height in the front and a roof of 3.5m height towards the back to feature two high windows. Image here "Front view" and IDF in this link.

I'm running with FullInteriorAndExteriorWithReflections, so I split the middle zone into two, a front zone (2.5m height) and a back zone (3.5m height) in two zones so that each zone is convex (as far as I could understand). But I still get errors such as

* Severe * Problem in interior solar distribution calculation (CHKBKS) * ~~~ * Solar Distribution = FullInteriorExterior will not work in Zone=ZONE_COZINHA * ~~~ * because one or more of vertices, such as Vertex 3 of back surface=PAREDE_LIVING_HALL, is in front of receiving surface=PAREDE_COZINHA_NORTE_ALTA * ~~~ * (Dot Product indicator= 10.6250) * ~~~ * Check surface geometry; if OK, use Solar Distribution = FullExterior instead. Use Output:Diagnostics, DisplayExtraWarnings; for more details.

that I understand is E+ complaining of zon-convex zones (I did check the geometry as best I could).

I thought I had two convex zones when I split them by different heights. I also tried to split the zones horizontally, with a bottom zone (2.5m height) from a top zone (only the clerestory), but similar errors occurred.

At this point, I'm unsure if there is an error in the geometry that I could not find or if I misunderstood how to fix a non-convex zone (or something else).

Any feedback on how to solve this is welcomed.

Many thanks.

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answered 2024-02-13 08:15:26 -0500

updated 2024-02-13 08:30:39 -0500

Hi @paula. This is what I think is happening.

First, the generated .shd report is confirming that all your zones are convex - no issue there. Yet adding an AirBoundary to "AirWall_Living_Cozinha" (separating "Zone_Living" from "Zone_Cozinha") instructs EnergyPlus to consider both zones as a single (now non-convex) zone for solar distribution:

The two zones separated by this air boundary will be grouped together into a combined enclosure for solar distribution, daylighting, and radiant exchange (including distribution of radiant internal gains).

Hence the severe errors. If combining 2 zones (via AirBoundary) results in a single convex zone, I don't think there would be an issue. I'm unsure of any quick geometry fix in your case. You may be limited to dropping "Interior" Solar Distribution options (e.g. "FullExteriorWithReflections" rather than "FullInteriorAndExteriorWithReflections") or opting for PixelCounting. I tried the latter: previous severe errors disappear - yet a single severe error on dynamic shading now pops up ... which may (or may not) be easier to address (depends on what you're after).

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Thank you, @Denis Bourgeois. Your explanation of how I created a non-convex with the AirBoundary made a lot of sense; I see the point now. I will explore both options you mentioned, simplifying the Solar Distribution and the PixelCounting (that I wasn't yet aware of).

paula's avatar paula  ( 2024-02-15 15:38:44 -0500 )edit

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Asked: 2024-02-05 08:24:32 -0500

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Last updated: Feb 15