Dear Community,
I hope everyone is doing well. I'm currently trying to replicate this study: "Im, P., R New, J., & Bae, Y. (2019, September). Updated OpenStudio (OS) Small and Medium Office Prototype Models. In Building Simulation 2019 (Vol. 16, pp. 1311-1317). IBPSA.". I'm using the DOE reference model for medium office building for Tampa 2A, 2013.
After I developed the baseline model (updated the spaces and corresponding model components based on the DOE modle), I started to iteratively update the four model parameters mentioned in this study based on this figure, 
I first redistributed the lighting power density using a space-specific scheme—let's call this model v1. In the baseline model, the lighting power density is uniform across all zones at 10.19587 W/m². I calculated the total nominal lighting power by multiplying each space’s area by its lighting power density. The baseline model has a total lighting power of 50,797.35 W, while model v1 has a slightly lower total of 49,947.00 W—a 1.67% decrease after the update. However, I noticed something counterintuitive when I reviewed the end-use results: cooling electricity consumption increased slightly, from 622.99 GJ to 623.15 GJ, despite the reduction in nominal lighting power. This building has three floors, each served by a dedicated air handling unit (AHU), with each AHU containing a DX cooling coil to meet the cooling load for all zones on that floor.
To understand the reason behind this observation, I first used the ideal load air system to examine the building dynamics after redistributing the lighting power density. The results made sense to me: after redistribution, district cooling energy decreased from 1993.59 GJ to 1983.08 GJ, while district heating energy increased slightly from 42.89 GJ to 42.94 GJ. Based on this, I assumed that the issue lies with the air handling unit models. Please note, nothing else was changed except for the lighting power density between baseline and v1.
I then checked the Cooling Coil Total Cooling Rate and Cooling Coil Electricity Energy and Cooling Coil Runtime Fraction . I noticed for all three DX coils, the average runtime fraction increases: ground floor - 0.5318 to 0.5324, middle floor - 0.4325 to 0.4331, top floor - 0.4233 to 0.4236. For Cooling Coil Total Cooling Rate and Cooling Coil Electricity Energy, I noticed that: the average cooling coil cooling rate and cooling coil electricity energy for ground floor slightly decreases, but for both middle and top floor, they increase. I'm stuck here wondering what should I further do to justify why the middle and top floor consumes more cooling energy. I also found that the cooling unmet hour decreases from 381.17 to 374.67.
I would greatly appreciate any insights you can offer on how to address this problem and which additional output variables might be helpful. Thank you so much for your time and support!
