Equal OA for ASHRAE 90.1 baseline and proposed in OpenStudio?

asked 2024-11-22 16:30:18 -0600

mattkoch
1081 ●10 ●8

updated 2024-11-24 17:29:02 -0600

14220 ●85 ●24 http://bigladdersoftware.com/

It sure would be nice to know how to configure in OpenStudioApp 1.7.0/OpenStudio 3.7.0 the ASHRAE 90.1-2010 Appendix G (Performance Rating Method) requirement for equal OA flows in the baseline and proposed building for a building with multiple variable speed AHU serving multiple simple reheat VAV terminal units. Aside from giving spooky results (like 100% OA) applying VRP to baseline and proposed would likely not give the same OA.

So for now, I am going by what the engineer tells me the OA/ft2 and OA/person requirements are (after their own VRP calculations), implement them as a DesignSpecificationOutdoorAir object for each space (can't apply them to a thermal zone), use ZoneSum everywhere and set OA flow rates in ControllerOutdoorAir and AirLoopHVAC to "autosize". This is me hoping that somehow the OA/ft2 and OA/person numbers in combination with identical occupancy schedules for baseline and proposed will yield said equal OA flows.

I'd welcome any thoughts advice. Thank you.

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Hello Twose10, and my apologies for the late reply. I am in the middle of a LEED project and just discovered last night that multiple runs of the same identical model give multiple results in OpenStudio. Not exactly encouraging. As far as I can tell, it has to do with which space's DesignSpecificationOudtoorAir (DSOA) is selected to represent a thermal zone. If not all spaces of the same thermal zone have the same DSOA then trouble arises The selection appears to be random.

mattkoch ( 2024-11-26 06:58:12 -0600 )edit

Be that as it may, yes, I would be very interested in learning more about your approach and have you guide me through the E+ Editor process. Perhaps it will also give me ideas for an OpenStudio script. How would you like to go about this? Is this something you have written up and can share, or do we need to touch base on the phone? Thanks.

mattkoch ( 2024-11-26 07:01:30 -0600 )edit

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Equal OA for ASHRAE 90.1 baseline and proposed in OpenStudio?

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Equal OA for ASHRAE 90.1 baseline and proposed in OpenStudio?