MSO, Your question was indeed answered however perhaps I need to better explain your situation. Basically an HVAC system is designed to Cool and Heat using specific guidelines published in the industry. In your case, there was decision made to not use a separate systems for the basement versus the other two floors. As a result, the total airflow volume is split between all three floors. In order to be most efficient, the engineered air flow must be maintained. That is 400 cubic feet of air must pass though the system for each 12,000 BTUs (1 ton) of capacity. Basements tend to be partially or fully below the ground and where the conditioned space is always different than the top floor for example. It is typically proposed to have a separate system to condition one of the three spaces. The majority of homeowners reject this approach since it tends to be more expensive. So they settle for a lees than optimum design that uses a slightly larger system to condition all three floors. The result, the top floor tends be warmer in the summer, and the basement tenses to be colder in the winter.
Since it is essential for the system to operate efficiently, you should not close the top floor vents in favor of more air in the basement and vice versa. This approach reduces the air flow and leads to much higher energy consumption. There are HVAC systems that operate on two or three stages to vary the capacity of the heating or cooling. These systems are more expensive and do use zone controllers to open and close different conditioned spaces using separate temperature controls in each of the zones. Basically, it varies the air and refrigerant flow.
The concept of creating “smart vents” is not exactly a bad idea, but the system would need to be smart enough to understand the entire HVAC system. Since we know that we need a low (0.3 to 0.5) total static pressure, the “smart vent” system would need to be able to calculate the total volume needed and maintain enough open vents at any specific time to achieve the designed efficiency of air flow. This fact would make that “smart vent” system very expensive and thus not consumer desirable. Additionally, the HAVC would need to be designed in such a way to accommodate the Smart Vents.
Frankly, the HVAC industry already achieves this ability with engineered Variable Refrigerant Flow systems with distributed air flow controls. These systems are very expensive and are typically used in commercial applications for office buildings to achieve the significant energy savings required by federal government regulations.
I hope this more detailed explanation helps you to understand the engineering that would be required to achieve what you feel would give you individually controlled smart vents and why it is not feasible.
Google Pro, Mechanical Engineer, Electrical Engineer and HVAC service company owner.
