Whole House Steam Humidifiers are used with Heat Pumps and Electric Furnaces. Low temperatures generated by these types of heating systems don't always provide enough evaporative heat to allow conventional humidifiers to function at full capacity. Whole House Steam Humidifiers use electric elements to heat reservoir water into steam. The whole house is then humidified by steam (moisture) produced by the Steam Humidifier. The steam vapor is sterile and mineral free. Whole House Steam Humidifiers are available as Furnace Plenum or Supply Side Air Under Duct mount.