The use of CO2 readings with fixed ventilation to predict energy savings with demand-controlled ventilation.

In a university building in Boston, IAQ complaints prompted an increase in outdoor air ventilation, causing a large increase in energy use. C02 readings were then taken in an auditorium, cafeteria, offices, and classrooms. The readings were used to calculate occupancy estimates and to simulate operation of a demand-controlled ventilation (DCV) system. The differential equations were solved in a spreadsheet program using a Runge-Kutta macro. A PID control system was also simulated. Ventilation adjustments were input to DOE-2 to estimate energy savings. A two year payback was estimated. DCV was also shown to provide a small savings when compared to lower design ventilation rates, while improving IAQ.