Condensation In Attic Ductwork

Ductwork located in an attic must be hung properly so that the insulation can do its job.

Condensation in attic ductwork.

It was new when the ac was put in 7 years ago. Condensation forms when warm humid air comes into contact with a colder surface like your air conditioner s ductwork. Moisture goes right through the fiberglass insulation and condenses on the inner liner drips on ceiling below after building up. All you need is a sag in the line or a level area and water will accumulate.

As the humidity level rises outdoors condensation will gradually begin to form on the surface of your air conditioning ducts. The 1 746 square foot house has r 19 insulation between the rafters and between r 15 and r 20 of rigid foam above the roof sheathing. When the hot humid attic air contacts the cold duct or the cold duct boot the moisture in the air condenses on the cold surface just like the condensation that happens on a cold can of beer. When ductwork is touching it forms a very cold spot where they are touching thus condensation begins.

There are two main ways to solve this problem. The colder the air the more likely it is that water will condense. If not condensation will form in the ducts when the heat hits the cold duct. Also whenever you cook and especially when you take a shower this will dump additional moisture into the attic ducts.

The colder the air is inside the duct the greater the chance of ductwork sweating. Condensation forms when warm moist air comes into contact with cool surfaces. The attic ductwork is flex duct work. Dripping condensation may also lead to a ceiling leak which not only looks bad but also rots drywall and can cause your ceiling to collapse over time.

Recently i had another hvac company come out and put in a new bathroom vent and they told me they believed the duct work was full of water. The air in your vented attic is hot and humid just like all outdoor air in florida. During periods of high humidity and high temperatures the conditions are ideal for condensation to form on improperly insulated ductwork in your home s attic. Vapor barrier on the attic side of the duct s insulation is compromised.

The last usual cause for condensation on a duct system is if the ducts are not properly hung or they are touching each other. Even though the air conditioning equipment appears to be operating normally humidity inside the house is between 60 and 65 and return ducts located in the attic show significant condensation. Condensation forms when the water vapor in the air drops out of suspension and condenses into a liquid form. I called out the original hvac company and they took a look and said they saw no water.