What causes duct work to sweat?
Sweating duct work is an environmental problem caused by low attic temperature and humid weather conditions. The duct work sweats when its surface temperature drops below the dew point temperature in the attic. Example 1. Poorly sealed ducts and ducts with holes cause condensation. When ducts are not properly sealed, cool air leaks into the attic environment. This causes the duct surface temperature to drop below the dew point, thereby causing the ducts to sweat. Example 2. Forced attic ventilation can cause problems. When the attic is ventilated, it draws outside air in and causes moisture levels and the dew point to rise. The duct work sweats because its surface temperature drops below the dew point. Since we change the weather, let’s look at ways to change the conditions in the attic. Solutions: 1. Don’t add an exhaust fan. It creates a constant supply of humid air entering the attic. 2. Increase the ambient temperature. Block the attic vents with plastic sheeting and install flood
