I’m living in a house that developed a huge mildew problem late in the summer. Like, mildew on literally everything, throughout the living space. In addition to running the air conditioner on dehumidify mode, using damp-rid containers, cleaning, and running a fan constantly, I got a hygrometer to see what the humidity is doing inside the house. What I found is that basically the house ends up whatever humidity it is outside, even with the AC running. I’ll go to bed with the house at 55% and wake up to it 70%, AC running the whole time. The AC has been cleaned and checked so it’s not the problem. The house doesn’t seem super drafty either. Could this be caused by a lack of vapor barrier in the walls? The humidity swings are so large and relatively quick that I’m confused as to where the moisture is coming from. Has anyone dealt with this before?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story

Engineered-stone shower panels are waterproof, but proper installation relies on tight seams and silicone sealing.
Featured Video
How to Install Cable Rail Around Wood-Post CornersHighlights
Fine Homebuilding Magazine
- Home Group
- Antique Trader
- Arts & Crafts Homes
- Bank Note Reporter
- Cabin Life
- Cuisine at Home
- Fine Gardening
- Fine Woodworking
- Green Building Advisor
- Garden Gate
- Horticulture
- Keep Craft Alive
- Log Home Living
- Military Trader/Vehicles
- Numismatic News
- Numismaster
- Old Cars Weekly
- Old House Journal
- Period Homes
- Popular Woodworking
- Script
- ShopNotes
- Sports Collectors Digest
- Threads
- Timber Home Living
- Traditional Building
- Woodsmith
- World Coin News
- Writer's Digest
Replies
Been in the house for a number of years and the problem just now developed? House have a crawl space?
Most of your humidity probably comes from your basement or crawlspace if you have one. A dehumidifier would be much more efficient at removing moisture from a house than an air conditioner .
I'd check to see if you have water leaking anywhere. Turn off everything and check the water meter.