You do have variations with the power venter. When the wind blows against your house, it changes the speed of the SWG motor. this increases or decreases the draw. If it increases the draft and there is no way to compensate the excess draw, your in for a hopper fire. If it decreases the draft and there is no baro to close and compensate for slow down, you'll have gas in the house. Everytime someone enters or exists the house, the pressure changes in the house, without a baro you would need to go and adjust the rheostat. The baro takes all the work out of it. Just like our thermostat.