The AprilAire 500M Whole-House Humidifier is designed for homes up to 3,600 sq. ft. The included manual humidistat lets you control the humidity level throughout your home. While balanced humidity exists between 40–60%, it's important to remember that outdoor temperature and other home factors will impact what relative humidity level is attainable and recommended for your house. You’ll enjoy balanced humidity thanks to the evaporative process, which works by passing hot, dry air from your furnace over the interior water panel to add moisture before returning the humidified air into your home using the existing blower fan in your HVAC system. The water panel is essential to the process, ensuring the removal of impurities from the water and providing uniform, high evaporation for whole-house humidification. AprilAire invented the whole-house evaporative humidifier in 1954, and this unit is designed and assembled in the USA utilizing US and global components. It offers multiple options for installation, making it simple to experience the benefits of balanced humidity throughout your living space.