I'd like to write expressions for zone keywords that are based on whether or not the zone/space is exterior or interior - primarily whether or not the zone/space has any EXTERIOR-WALLs. In particular, I'd like to change the default for ZONE:AUX-HEAT-RATIO so that baseboards in exterior zones have a high capacity, and baseboards in interior zones have zero capacity (no baseboard). Here are a few things I've thought of that don't help:
1. The ZONE can reference SPACE keywords through the #RV(#LR()) nested function, but I'm not aware of any SPACE keywords that identify exterior/interior status.
2. There is a ChildCount() function (abbreviated version is #CC()) that I think could be used to determine if a SPACE has any EXTERIOR-WALLs, but I think it is only valid for doing a Compliance Analysis.
3. When starting a model using the Wizards, infiltration schedules are automatically created with "P-Inf" and "C-Inf" in the name, based on perimeter/core. I could reference the SPACE:INF-SCHEDULE, but the schedule names that are automatically generated can vary somewhat. Also, I typically create a single infiltration schedule to apply to all spaces in order to meet the ASHRAE 90.1 G3.1.1.4 requirement for air leakage as a function of floor area instead of exterior envelope area, for the same reason that I can't write an expression that's based on whether or not a space has any EXTERIOR-WALLs.
4. I could manually describe a space as exterior or interior by adding "-ext" or "-int" to the SPACE:C-ACTIVITY-DESC. (For example, I could describe a classroom with an exterior wall as "Clas-ext".) Then I could replace every instance of "required" in the default expression for ZONE:AUX-HEAT-RATIO with the following expression:
switch (#LR("SPACE","C-ACTIVITY-DESC",1)) $ 1 is for 2nd set of four characters
case "-ext": 1.0
case "-int": 0
default : 0.5
endswitch
However, that's about as much work as manually entering the value for AUX-HEAT-RATIO. Though it could streamline things if I had more than one custom expression that took advantage of the SWITCH statement.
I will write a clerihew
Thanks!
~Bill
William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer
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