Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Yeah, this is kind of a problem with energy modeling tools and daylighting. The energy model is essentially thermal zone-centric, and geometric coherence kinda-sorta ends at the building perimeter. Those thermal zone boundaries are indeed opaque to the daylighting calculation in EnergyPlus, regardless of whether those boundaries are physical or logical.
With CBECC, EnergyPlus is doing all of the modeling, so you need to make do. ASSuming that extending the perimeter thermal zone to a depth of 20' does not skew your HVAC reality too much, that'd be the way to go. You can then have EnergyPlus do the daylighting calculation, and realistically you're not gonna get good side penetration of daylighting beyond 20' anyway, even with that head height of 11' (unless the ceiling is higher still, and you are using daylight redirection devices, and...). Just make sure you use two daylight sensors, locate them sensibly, and you fairly assign the percentages that each one is controlling for each zone.
And, if I may shamelessly shill for it: OpenStudio allows you to set these interior thermal zone boundaries as "air walls", which when simulating the daylighting in Radiance will not be exported, thus giving you an honest architectural model for the daylighting simulation. Not an option for CBECC, but...
