Persily et al. [5] modeled DCV with various assumed minimum ventilation rates when CO2 concentrations did not exceed the maximum CO2 set point. The minimum ventilation rates modeled were as follows:

• DCV 1. No minimum ventilation.
• DCV 2. A minimum ventilation rate of 25% of the rate specified in ASHRAE Standard 62-2001.
• DCV 3. A minimum ventilation rate per floor area based on the requirements in ASHRAE Standard 62-2001.
• DCV 4. A minimum ventilation rate per floor area based on the requirements in California’s Title 24 Standards.

A fixed minimum ventilation rate as specified in ASHRAE Standard 62-2001 [6] was the reference case.

For the first three DCV options listed above, the maximum CO2 concentration was the concentration predicted at steady state with design occupancy and a fixed ventilation rate as specified in ASHRAE Standard 62.1-2001. For the final DCV option listed above, the maximum CO2 concentration was 800 ppm.
Only DCV 4 complied with Title 24 standards (Figure 1). The percentage reductions range from -17% to 0% for the office building, 64% to 72% for the conference room, 32% to 43% for the lecture hall, 40% to 60% for the classroom, 13% to 25% for the portable classroom, and 52% to 76% for the fast food restaurant. The report by Persily et al. [5] also provides additional details, including the predicted heating, sensible cooling, and latent cooling loads.

Table 1. Ventilation Heating and Cooling Load (MJ/m²)
(a) Office Building

(c) Lecture Hall