Often each floor of a building has an air handling system consisting of a plant room, ducting and equipment such as fans and heaters. The cost of the system consists of the capital cost of the equipment and the operating cost to satisfy the thermal loads. An efficient method is required for evaluating the operating costs when the configuration of the system is specified and the thermal loads are known. The operating cost of a particular configuration are obtained by solving a nonlinear program. The method is efficient since it consists of solving a sequence of single period models
