Why is my ductwork dripping condensation inside the walls?
Ductwork running from unconditioned spaces into wall cavities collects condensation on its exterior, causing water to drip into walls. This moisture leads to severe fungal growth and structural damage that often requires tearing out the walls.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1ripping out walls
- 2Insulating the vent line if it passes through the attic to manage temperature differences.
- 3Insulating the sheet metal externally or internally
- 4Asking online for advice on whether to use a dehumidifier, rewrap ducts, or replace them entirely.
- 5Insulating the ducts
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“This was the second summer our living room ceiling had condensation seeping through from our ducts.”source ↗
“We have discovered that the ductwork in our walls of the second story have been dripping condensation from the outside into wall cavities.”source ↗
“Needs solution as we are having to rip out walls due to fungal growth.”source ↗
“Noticed water condensing on the closed vent, and saw this. Is it frost? Will I need to replace it?”source ↗
“When I removed a large 4x7 foot patch of drywall due to water damage related to a badly piped condensate line there was a square of plywood sitting between the sheet metal of the plenum and the ceiling drywall downstairs.”source ↗
“I want to replace the drywall I removed but need suggestions on insulating the plenum box.”source ↗
Where this came up
People with this problem also raised
- 9AC unit leaking water from top rubber seal
- 2Why is there condensation and damp spots on walls only on laundry days?
- 5What is this extra pipe dripping into my sink drain?
- 2How to stop birds from nesting in high dryer vents without cleaning a clog
- 2how to keep cold air out of mesh windows
- 3Basement window level with the ground water leak prevention