Sweating Ducts

May 5, 2021

Duct Sweating

Ducts in your attic sweating is not the same as your body sweating. Ducts that are sweating are more like your car having those beads of condensation in the morning. This map of the US shows Florida fully contained in the area with the highest seasonal dew point. When an object reaches the dew point temperature, condensation starts to form (we call it sweating).

About Duct Sweating

There is a complex formula for the calculation of a homes ductwork meeting the dew point. Some important things a homeowner needs to know:

- the air inside your ducts is about 20 degrees below your room temperature when your AC is cooling.
- if you lower your thermostat to 65 degrees at night, the 45 degree air temp inside your ductwork will cause the temp of outer skin of your ducts to fall below the dewpoint on every summer night.
- People who live near the water (higher humidity areas) or have a tile roof (cooler attic temperatures) have a greater possibility of duct sweating problems.

Sweating Ductwork is a major and complex problem and has no quick fix. The good news is that the best fixes start with giving your AC system a tighter seal and thus making it more efficient. Difficult fixes involve replacing ductwork with better insulation or even replacing home insulation with spray on foam. After the repair investment these fixes pay for themselves over time with energy savings.