An HVAC or a Small-Duct High-Velocity system is a central air-distribution system made of very small ducts that deliver conditioned air into the room using small jets of air that actively mix the room air without creating drafts.
SDHV systems are smaller, quieter, and more comfortable systems than traditional air distribution systems. Plus, their small ducts add cubic feet to over headroom and dramatically reduce the need for unused room between the ceiling and the next floor