The beneficial effects produced by residential humidifiers have long been recognized. Only recently has it been generally acknowledged, however, that humidification is not free, but rather requires energy. Humidifier energy is proportionate to the amount of moisture evaporated and is generally supplied (indirectly) by the central heating system. With the need for energy conservation on all home appliances, it becomes vital to consider and control the seasonal energy usage of humidifiers.

Practically no reliable information is available on the seasonal energy used by humidifiers. This is partly due to the general belief that humidifiers are not major energy users. It is also due to the fact that humidifier performance and energy use is related to so many independent variables, including house type, size and location, as well as furnace type, size and controls, whose effects on the humidifier are unknown, that any simple calculation or test is of little value. Similarly, while it has been generally accepted that use of humidifiers can produce equivalent comfort sensations at reduced thermostat settings, this phenomenon is also very complex and difficult to, quantify by test. Reduction of the thermostat setting generally produces significant energy savings by itself--often more than is required for the humidification process. But these trade-offs, while noted, are not investigated specifically in this study.

The complexity of the situation regarding central system humidifier application and energy usage almost rules out any systematic field or lab test programs as means of obtaining comprehensive information. An accurate computer simulation model therefore becomes an invaluable investigative tool for both product design and application. The present paper describes a basic mathematical model for a central system type humidifier and, using a computer program developed from the model, presents general application and seasonal performance guidelines for central system humidifiers.