What to Do About Water Around A/C Vents

Vent moisture is a seasonal event in some houses, normally occurring only during the summer when cold air from the A/C flows through supply vents into rooms. You may notice vent moisture simply by touching the vents during normal housekeeping or you may actually see dripping occur. In more severe cases, the wall around the vent may become stained due to chronic exposure to moisture formation on the vent.

Here are some probable causes and cures of excess vent moisture in summer.

Uninsulated Ducts

During the summer, HVAC ductwork routed through an unconditioned attic is exposed to hot and very humid air. When the A/C is running, air flowing through the ducts is comparatively cold. As hot, humid attic air contacts frigid ducts, condensation occurs. While some of this moisture dribbles into the attic (often saturating insulation) some typically forms closer to the termination of the duct and drips out around the supply vent.

The most direct solution to condensation formation is to wrap the ducts with air duct insulation. This keeps hot, moist air from contacting cold metal duct surfaces and condensing. It also helps cooling performance by reducing thermal transfer of heat into ductwork airflow.

Duct Leakage

Residential ductwork frequently becomes leaky over time. When leaks in supply ductwork occur, warm, humid air may enter the cool A/C airflow and trigger formation of condensation inside the duct itself. If the air leak is close to the supply vent, condensation may dribble to the vent opening and into the room.

A qualified HVAC professional can inspect the ductwork for leakage, then suggest options to seal any leaks and prevent infiltration of warm humid air that causes condensation inside ducts.

Other Suspects

Issues at the A/C evaporator coil including insufficient airflow or low refrigerant charge, or a system that runs short cooling cycles, can inhibit proper humidity extraction. Overly humid A/C airflow may form condensation where it enters rooms through the supply vent. An HVAC service technician can troubleshoot the problem and restore proper dehumidifying function.

For professional service to resolve vent moisture problems, contact Energy 1 Heating & Air Conditioning.

Our goal is to help educate our customers in Lorain, Ohio about energy and home comfort issues (specific to HVAC systems). For more information about other HVAC topics, download our free Home Comfort Guide or call us at 440-201-2959.