Supply ventilation – energy use impact
I downloaded BEOpt and EnergyPlus and have been experimenting. Some of the outputs are surprising at first but make sense when I think more deeply, However, I have not been able to make sense of the results I am getting for different ventilation options. I am trying to determine if there is some physics advantage to supply ventilation or whether the results I am getting are modeling errors.
I have four cases: no ventilation, exhaust, supply, and 70% efficient HRV. The later three all use the same ventilation rate in cfm. The software reports the source energy used per year for various categories. The source energy for heating comes out:
The relative values make sense for none, exhaust, and hrv. But why wouldn’t supply be about the same as exhaust? In each case, you are bringing in the same quantity of unconditioned air. The fan vent energy is the same for exhaust and supply. (It goes up dramatically for HRV, making the total energy for HRV higher than for supply.) The HVAC fan energy is close, with exhaust being slightly higher than the other three. I would have expected supply to be higher in that category if the software is modeling a CFIS system.
The software automatically determined the following heating capacities:
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