Problem of identifying heating EUI using DOE pre-1980 medium office building model

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I'm now doing a simulation using DOE medium office building,pre-1980 model. One important value I need to find out is the EUI for heating,but I came across some problems of identifying it. I'll be really appreciate if anyone could kindly help me on this.

In this model, heating is supplied only by gas. There is an item called 'Natural Gas End Use for Heating' in the results report (html file), and an item called 'Natural Gas Intensity for HVAC'. Shall I get the heating EUI by 'Natural Gas End Use for Heating/ Area', or shall I use 'Natural Gas Intensity for HVAC' as heating EUI?

What I really confused about is that 'Natural Gas Intensity for HVAC' is calculated from '(Natural Gas End Use for Heating+Natural Gas End Use for Water System)/Area' , but water system is not supposed to be part of HVAC system...Does anyone know why it's like that?

To be put into a separate question

One last point to add, I changed heating setpoints, found out that no matter how low the setpoint is(even 32 degree F), 'Natural Gas End Use for Heating' and 'Natural Gas Intensity for HVAC' are not equal to 0, they could not go down after reaching certain values (when the setpoint is approximately 60). It's another problem I need be helped with.