Dehumidifiers work by removing the humidity from the air. Generally, you will see these units in a basement where the damp, humid air can cause a musty smell and possible bacteria growth. The size of the unit and the amount of moisture the unit can remove are important factors when buying the right dehumidifier. The relative humidity for a basement should be about 30 to 40 percent during the summer and winter.
Moderately Damp
Basements that have a musty smell and feel damp when the weather is humid are considered moderately damp according to Energy Star. The correct size dehumidifier needed for a moderately damp basement that is 1,000 square feet would be a unit capable of removing up to 14 pints of water in 24 hours.
Very Damp
Very damp conditions will have a musty smell and feel damp all the time. The floors and walls will have damp spots. The correct size dehumidifier for a 1,000 square foot basement would be one that can remove almost 17 pints of water per day.
Wet
A 1,000 square foot basement that has seepage from the outside or the floors and walls sweat are considered wet when it comes to sizing the dehumidifier. The room will smell of wetness and feel extremely damp, almost wet. Dehumidifiers that can remove almost 20 pints of water in a 24 hour period will be able to lower the humidity and dry the basement.
Extremely Wet
Rooms that have laundry drying, a high moisture load or the floors are wet, will need a larger size dehumidifier to remove more pints of water in a 24 hour period. Extremely wet basements 1,000 square feet will require a unit that can remove at least 23 pints of water per day.
Overall Size
Dehumidifiers are generalized in size for the amount of water it can remove from the air in a 24 hour period. For an 1,000 square foot basement that is moderately damp, very damp, wet or extremely wet, you would need a portable humidifier that can remove at least 23 pints of water from the air and is rated for a room 1,000 square feet. A 30-pint dehumidifier that covers 1,100 square feet will be sufficient for the basement. Always add 100 square feet onto the room size total square footage. Bigger is always better when selecting a dehumidifier for a basement that can have changing conditions.