They built an outgoing duct that sent the warm air into the parking garage and then realized that they really needed the warm air back inside. If they just blocked the outgoing duct, then the job would be over and someone might say that they had wasted time and money putting in the outgoing duct in the first place. So instead they built an ingoing duct which not only prolonged the job and kept them employed, but also caused the outgoing duct to necessary because where else would they get warm air to send into the ingoing duct.
I believe that this is symbolic of many of our more highly developed political processes. But I could be wrong.