Comparison of air distribution system alternatives serving a classroom-office portion of a school building

An effective air distribution design accomplishes both comfort and ventilation requirements while consuming as little energy as possible. This paper analyzes four different air distribution systems and technologies including single duct variable air volume air handlers, chilled beam cooling systems, total energy recovery wheels, displacement ventilation, and dedicated outside air systems in an effort to compare air distribution systems for a representative section of a school in hot and humid climate. Distribution effectiveness and energy consumption are weighed against considerations such as system complexity and cost. Energy modeling calculations show that the Energy Utilization Index (EUI) of all of the analyzed designs are significantly less than the median EUI of schools in south Texas. Chilled beams are not well suited for schools because of the large amount of outside air required by the space and the sophisticated design and operation needed to prevent condensation from occurring at the chilled beam. Payback calculations show that even though new technologies like displacement ventilation and dedicated outside air systems reduce total energy consumption, they are not realistic design solutions because they have paybacks that exceed 100 years. The calculations also show the total energy recovery wheels result in a 16% energy savings over a baseline central variable air volume distribution system because of the large amount of outside air required in school buildings.