Dual ventilation fans and natural ventilation in the same room. Fans are used in cold months and in warm months, shut off as the sidewall curtains begin to open up. Exhaust that is too low or too high impacts energy by wasting dollars. Excess drafting from gusty winds through open sidewalls is also eliminated. With a 16-km per hour wind, a naturally ventilated barn can achieve about four times the airflow than that of a fan system. Energy dollars can be saved by not having to run the fans. Estimated fan operating costs for a dual system are 25 cents per pig compared to $1 to $1.25 for a conventional fan ventilated barn.