My $120 bathroom vent fan install turned into a moldy mess

I tried to replace my old fan myself last fall, thinking it would be simple. I cut the new hole in the ceiling, hooked up the duct, and thought I was done. But I didn't seal the duct connection to the outside vent with mastic tape (I just used the cheap foil stuff). Six months later, I found a damp spot and had to rip out a section of wet, moldy drywall. Has anyone else had a vent fan fail because of a bad seal, and how did you fix it right?

2 comments

2 Comments

craig.reese3d ago

Oof, that foil tape is basically useless for a real seal, isn't it? You need that mastic paste or the special aluminum tape labeled for ducts. Did you think the foil stuff was enough because it looks shiny and tough? Once the drywall is open, slapping on a thick layer of mastic over every single seam and joint is the only way to stop that damp air from leaking back in.

hall.ruby3d ago

Craig.reese is totally right about the foil tape, it just doesn't stick for long. I learned that the hard way after my own basement stayed musty for months. The mastic paste is messy but it actually works, sealing everything up for good.