Patent ID: 8423192

Claim:
A method of controlling an existing heating, ventilation, and air conditioning system, said existing heating, ventilation, and air-conditioning system configured to condition at least one zone and having at least one terminal box, and a plurality of control components, said method comprising: integrating a controller into said existing heating, ventilation, and air conditioning system such that said controller is in communication with said at least one terminal box and said plurality of control components, said controller programmed with a carbon dioxide baseline value for said existing heating, ventilation, and air-conditioning system and a fresh air requirement for said at least one zone; integrating at least one outside air sensor and at least one primary air sensor into an outside airflow and a primary air flow of said existing heating, ventilation, and air conditioning system, said at least one outside air sensor and at least one primary air sensor connected in signal communication with and configured to measure and send to said controller at least one of a primary air carbon dioxide measurement and at least one of an outside air carbon dioxide measurement in said existing heating, ventilation, and air conditioning system; calculating, by said controller, a primary air freshness for said at least one zone comprising finding one minus a ratio of the difference between said primary air carbon dioxide measurement and said outside air carbon dioxide measurement over a difference between said carbon dioxide baseline value and said outside air carbon dioxide measurement; generating, by said controller, a minimum airflow set point for said at least one zone comprising finding a ratio of said fresh air requirement over said primary air freshness; controlling said existing heating, ventilation, and air conditioning system comprising modulating said plurality of control components based on said minimum airflow set point.