Method for separate control of HVAC for a vehicle

A method for separate control of heating, ventilating, or air conditioning (HVAC) for a vehicle, the method comprising steps of:

• determining if a set condition is satisfied, such that separate HVAC control is possible, when HVAC is performed;
• detecting a passenger count, an HVAC thermal load, and a relative humidity;
• performing HVAC in a first mode for front seats including a driver's seat and a front passenger seat, when a passenger is detected in a front passenger seat at the detecting step;
• selectively performing HVAC in a second mode for the front seats, including the front passenger seat, by comparing the HVAC thermal load with a set load when no passenger is detected in the front passenger seat at the detecting step;
• and
• adjusting a mixing ratio between inside and outside air, set depending on the relative humidity, by selectively reducing or increasing a quantity of inside air and a quantity of outside air depending on the passenger count when performing HVAC for the front seats in the first and second modes,
• wherein adjusting the mixing ratio between inside and outside air when performing HVAC for the front seats in the first and second modes includes adjusting the mixing ratio between inside and outside air based on a reference mixing ratio set based on the passenger count being two.