The natural air flow of any home is up. Air is pulled from the lowest level and introduced throughout the home. The vehicle for this flow is heat. Of course everyone that graduated middle school knows that heat rises and cold falls. As the heat rises it is replaced by cooler air, this is what creates the natural air flow of the home. Whether you are heating the home in the winter or fighting it off in the summer the heat will always dictate the circulation direction. The natural air flow, also called the stack effect, will continue to move the air in your home toward the roof unless you allocate sufficient resources to change it. In my opinion, using mechanical vents to change this natural condition is an attempt to reinvent the wheel. It will not stop the warm air from rising, it is not a sufficient resource to change the natural air flow in the home and it will leave the homeowner with a failed concept that was backed by a great sales pitch, while still owning the problem. Granted the problems will be lessened and less frequent but nonetheless – not extinct.