Have ample space you need to humidify? Are Ultrasonic and steam units not able to keep up with the amount of square footage? Ultrasonic units are typically smaller and can't compete with the output of a large, whole house humidifier. For larger homes – 1,000 square feet and bigger – evaporative humidifiers are the winner. Here are our best-rated humidifiers for spaces larger than 1,000 square feet.