School District, Hillsborough County (Tampa, FL)

Complaints about organic odors and high humidity levels at two Hillsborough County High Schools prompted an investigation and analysis of the HVAC system design. The system controls incorporate a discharge air temperature reset, which increases air temperature at low cooling loads in order to decrease energy use. Furthermore, the reheat system had been turned off in an attempt to comply with Florida Energy Code. Unfortunately, the design resulted in decreased system dehumidification capacity at low sensible loads – just when humidity control is most critical. An hourly computer building model was developed using DOE-2.1e and Visual Basic to simulate control sequences and arrive at low cost, innovative modifications to reduce humidity. The modifications were implemented and solved the air quality problems; while at the same time reducing energy costs as compared with reactivating the hot water reheat system.