Condensation

• Air ducting "sweating" occurs due to a scientific phenomenon known as condensation. Condensation occurs any time a cool surface comes into contact with hot, moisture filled air. An example of condensation familiar to most people is the gradual pooling of water that occurs underneath a glass of a cold beverage on a hot and humid day. In order to prevent this process, you will need to find a way to prevent the warm, humid air from touching the cool surface of the air duct.
  
  

Problems

• Besides allowing water to accumulate on materials that tend to rot when exposed to large amounts of water, condensation also increases the likelihood of a growth of mold and cause the rusting of metal building materials. Condensation could even allow water to get into the electrical system, a recipe for disaster if ever there was one.
  
  

Duct Wrap

• The first strategy is to enclose all sheet metal ducts with duct wrap. This substance, made of fiberglass, warms the surface of the air duct and prevents condensation. Before applying the duct wrap, you will need to double-check that all the joints in duct system have been sealed with mastic.
  
  

Duct Board

• A more efficient solution is to avoid sheet metal ducts all together and use instead a fiberglass duct board and flex duct system. This system creates an airtight duct system well insulated against outside air, preventing condensation and ensuring that less of the cooling power of the air conditioner goes to waste.