The Aprilaire Whole-House Humidifier features a built-in bypass damper and comes in different models for all sized homes.

The Aprilaire Whole-House Humidifier:

• Installs into your central heating and cooling system ductwork
• Comes equipped with a drain to flush minerals from the unit
• Has an evaporation capacity of 0.50 gallons per hour
• Humidifies tightly-constructed homes up to 3,000 square feet in size

source: aprilaire.com