Excess humidity inside your home for a prolonged period of time can damage walls, especially when outdoor air temperatures are very cold. Your humidistat is set too high if excessive moisture collects on windows and other cold surfaces. Other sources of excess moisture besides overuse of a humidifier may be long showers, running hot water for long periods of time, boiling or steaming foods, certain plants, and drying clothes indoors. A tight, energy efficient house holds more moisture so you may need to run a kitchen or bath ventilating fan at times or open a window briefly. Storm windows and caulking around windows keep the interior glass warmer and reduce condensation of moisture there. Humidifiers are not recommended for use in buildings without proper vapor barriers because of potential damage from moisture buildup. Consult a building contractor or an inspector to determine the adequacy of the vapor barrier in your house. Use a humidity indicator to measure and monitor the relative humidity in your house.
Anne Field, Extension Specialist, Emeritus, with reference from the Association for Home Appliance Manufacturers (www.aham.org/).