TECHNICAL FEATURE It is possible to add a recirculating warm deck air-handling unit to an existing VAV air system and change out the terminals from single duct reheat to dual duct terminals. This approach is more feasible if there is space for the warm deck air-handling unit and the distribution terminals are in an easily accessible location. Also, careful evaluation of the existing VAV unit fan capacity turndown should be investigated. Consideration must account for the additional space requirements of the dual duct system in a retrofit situation. Possible solutions may include stacked air handlers or rooftop equipment. In the evaluation of replacing the existing operating suite system, credit savings in the hospital infrastructure capacity to the replacement system. Considerable savings in boiler and chiller plant capacity will be achieved and this capacity will be available for future additions and renovations. The operating suite needs to be supported by utilities that are on emergency power and this may relate to www.info.hotims.com/54427-55 further infrastructure savings. Also, if the central plant capacity is judged to be marginal, replacing the operating room system may be a better solution than increasing the capacity of the plant. Conclusions It has been demonstrated that the energy demands of an operating room HVAC system can be mitigated by a dual duct air system, as compared to a well-controlled conventional VAV two-position system. The proposed dual duct system has a higher installed cost, but will provide a favorable payback for many applications. The changing of the paradigm of what is the optimum system to be applied to the operating room is one of the changes required to address the high energy requirements of the hospital. References 1. ANSI/ASHRAE/ASHE Standard 170-2008, Ventilation of Health Care Facilities. www.info.hotims.com/54427-12 APRI L 2015 ashrae.org ASHRAE JOURNAL 41