Watch the hot water tank
Put a battery-operated floor-water alarm near your hot water tank, so you’ll be alerted if the tank starts to leak. If you have a central alarm system, consider having a floor-water alarm tied into the system. If you have a gas-fired hot water heater, plan to replace it right before the warranty expires. Electric hot water heaters tend to last longer than their warranty, but still, keep an eye on its warranty date.
Dry up the drips
Even a small water leak can develop into a major mold problem, so check pipes under sinks, and behind your washing machine and refrigerator (if it has a water line).
Repair leaks right away.
Don’t be sloppy when watering your indoor plants
I can’t tell you how many homes I’ve seen with moisture stains on the floor under or near an indoor plant. Be careful not to spill or overwater when you are watering a plant and put a dish under the pot in case the pot leaks. It’s also not a great idea to put a plant pot on a carpet or rug.
Isolate your crawl space
A crawl space should be isolated from the exterior and be dehumidified. Otherwise, humid air can enter the space and lead to condensation and mold growth on cool surfaces. If a crawl space has a dirt floor, the dirt should be covered with a mesh-enforced vapor barrier, or even with appropriate cementitious material, to limit the evaporation of moisture from the soil.
Don’t keep some rooms cold while you heat other rooms
In the winter, it’s tempting to heat only the rooms that you use and leave other rooms cool. In homes with wood-burning stoves, I’ve often found that some rooms near the stove are toasty, while others are uncomfortably cold. This may help you save on your heating bills, but unfortunately, elevated RH conditions can develop in the rooms that aren’t adequately heated, even if they are above grade. And then you know what may happen next… mold growth.