Abstract: The present invention is related to the field of heating, ventilation and air conditioning (HVAC). More particularly, the present invention is related to methods and systems for controlled heating and cooling in order to reduce costs and the carbon footprint of said heating and cooling by optimizing the use of fresh air ventilation. The present invention is directed to mathematical algorithms incorporated into a controller and a method of determining control signals that are dependent on said mathematical algorithms and user programming that integrates information from multiple sensors, thermostats as well as weather information. Used in any home or building, the controller controls heating, cooling and ventilation systems in order to reduce costs and the carbon footprint of said heating and cooling by optimizing the use of fresh air ventilation. The controller works with typical HVAC systems generally in buildings and homes.