How to stop mold and high humidity ruining a basement
Basement humidity hitting around 80% creates a persistent musty smell and mold growth on furniture, fabrics, and cardboard boxes. This excess moisture risks spreading mold spores throughout the rest of the house, threatening stored items and equipment.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Using a dehumidifier with a condensate pump
- 2Creating air vents to the exterior on ground level to force airflow
- 3Spraying surfaces with bleach to temporarily kill mold
- 4Running a dehumidifier constantly
- 5Spraying mold remover like RMR multiple times
- 6Removing damaged or moldy framing
- 7Opening basement windows and using a fan
- 8Keeping connected HVAC systems turned off
- 9Using a dehumidifier
- 10Installing a U.V.C light in the air handler
- 11Adding a vent in the return to circulate air
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Humidity is around 80%, and there's a persistent musty smell. What appears to be mold keeps developing on old furniture, fabrics, cardboard boxes, chairs and even some cables.”source ↗
“A spore test in the basement showed an amplification over the outside of Aspergillus/Penicillium of 1273 counts per cubic meter near the cold room and 796 in the rest of the basement.”source ↗
“While the rest of the house showed an acceptable spores count, isn't it possible for the spores to spread through the house from the basement?”source ↗
“West Coast FL upstairs Air Handler closet sweating plenum (humid control issue) and mold growing.”source ↗
“Mold has been like this for a bit and there is no issues inside duct work have tested around house but not sure what to do getting all kinds of conflicting information.”source ↗
“What's best way to control the humidity issue and clean this up?”source ↗
Where this came up
People with this problem also raised
- 4Why are my metal floor vents sweating and growing mold?
- 2Why is there condensation and damp spots on walls only on laundry days?
- 8How to clean mold under water damaged flooring without DIY experience
- 10Why is my AC not lowering indoor humidity?
- 2Why is condensation causing mold and ruining my appliances?
- 3Can you use fiberglass insulation in a basement after flooding?