An office building has a two-level enclosed parking garage with a total capacity of 450 cars, a total floor area of 8,300 m2 (89,290 ft²), and an average height of 2.75 m (9.0 ft). The total length of time for a typical car operation within the garage is 2 minutes (120 s).

a. Determine the required ventilation rate for the enclosed parking garage in L/s·m² (or cfm/ft²) and in ACH so that CO levels never exceed 25 ppm. Assume that the number of cars in operation is 40 percent of the total vehicle capacity (a shopping mall facility).

b. Determine the annual fan energy savings if the ventilation found in

(a) is used instead of 1.5 cfm/ ft², recommended by ASHRAE 62-1989. The ventilation system is operated 16 hours/day over 365 days/year. The rate of electricity is $0.07/kWh. Assume the size of the initial ventilation fan is 30 hp (22.9 kW).