Mold prevention and maintenance

Buy a cheap hygrometer and put one in the basement and one on the main floor. Humidity is the number that predicts mold, and most people have never measured it in their own house. If the basement reads above 60 percent in summer, a dehumidifier is a far cheaper purchase than remediation.

Ventilation is the second lever. Bathroom and kitchen exhaust fans need to discharge outside the building, not into an attic or soffit — attic sheathing mold is very often a bathroom fan terminating in the wrong place. Run the bathroom fan during showers and for a while afterward.

The third lever is the boring one: fix leaks fast. A dripping supply line, a failed toilet wax ring, clogged gutters dumping against the foundation, or grading that slopes toward the house are the everyday causes of the mold jobs that cost thousands. The EPA's guidance is to correct water problems promptly and dry all items completely.

One thing not to buy: air purifiers marketed as mold treatment. They may filter airborne spores, but they do nothing about the wet material the mold is growing on.

How to choose

Measure humidity, don't guess

Target below 60 percent, ideally 30–50 percent relative humidity, per EPA guidance.

Check where your fans vent

Bathroom and kitchen exhaust must terminate outside. Attic or soffit discharge is a common cause of attic mold.

Treat every leak as a 48-hour deadline

Drying inside 24–48 hours usually prevents mold entirely and costs almost nothing.

Manage water outside the house too

Clean gutters, extend downspouts, and slope soil away from the foundation. Basement mold usually starts outdoors.

Skip mold-killing gadgets

Ozone generators and air purifiers do not address wet building materials, which is where the mold actually lives.