My 2 sewing rooms (2 small bedrooms turned into a sewing and fabric room, and a cutting and ironing room) and family room are in the basement. In WI, the summers can get hot and humid so the AC runs fairly often. Even with the central air on, I use a dehumidifier in the family room as the system is older and not as efficient. Anytime there is dampness, a dehumidifier should be running. Anyone with asthma, arthritis and/or chronic conditions may attest. And us sewers know to treat our quilting stashes and investments like we would ourselves, right?