Natural Ventilation and HVAC system Usage    
   Hi..
Natural Ventilation (passive) and HVAC (active) are two major methods of ventilating the building. I have couple of questions about these two.
- If natural ventilation is active (open window), does the HVAC system still operate in Energy Plus simulation? 
- Suppose my dual thermostat setpoint temperature is set at 20C for heating and cooling. My outdoor temperature is 15 C and my window is open. To maintain my thermostat temperature, my HVAC system needs to operate. Which Output:Variable should I use to calculate the heating load required to maintain my zone temperature at 20 C? 
Thanks..


 
  
 
