Engineers retrofitting non-air conditioned schools to variable refrigerant flow (VRF) the last few years have relied on centralized packaged DOAS to comply with ASHRAE 62.1 outdoor air standards.

However, en route to providing a VRF retrofit solution for four Union County Public Schools (UCPS) in Maynardville, TN, engineers and contractors may have originated a new trend. They decentralized outdoor air because the schools' limited ceilings weren't practical for ductwork from a centralized unit. Thus UCPS's engineers and contractors developed what may be, to their knowledge, the industry's first VRF and dedicated enthalpy wheel combination self-contained inside a unit ventilator-style encasement. What's innovative is that these efficient 32-in (H) by 104-in (L) by 30-in (D) unit ventilators with an VRF/enthalpy wheel are easy drop-in replacements for conventional ventilators that have dominated the classroom HVAC market the last 50 years.