Humidifiers and Dehumidifiers

Whole-Home Humidifiers

Bypass & powered flow-through systems

There are several types of in-duct humidifiers. Which you choose might be determined by preference or by necessity. Steam and drum humidifiers can work best in certain situations.

Bypass humidifiers are usually mounted on the air-return duct, connecting to the hot air supply using a supply-takeoff duct. The supply takeoff diverts heated air to the humidifier using natural pressure differences between the supply and return sides. The warm air picks up moisture from an evaporator pad and returns to the furnace. Some bypass humidifiers are mounted directly to the hot air duct.

The good:

  • Low cost
  • Hard-water tolerant
  • Easy, infrequent maintenance (change filter yearly and check drain tube for buildup of minerals)
  • Easy installation (no heating element, no fan and no drum motor)
  • Less noise
  • No stagnant water for bacteria to grow in

The bad:

  • No separate motor or fan, meaning it only works when the furnace is on
  • Higher rate of water use. Little is actually converted to humidity; instead, it's flushed through the pad to minimize clogging from mineral buildup.

Powered flow-through humidifiers work the same way as bypass but include a fan to blow air across the moistened pad for increased water evaporation. They can generally produce a gallon more humidity each day compared to a bypass model. The electricity required for the fan equals that of a 25-watt light bulb. Powered flow-through systems don't need a bypass duct, meaning they can be installed in smaller spaces. They are perfect for homes built on slabs or with HVAC systems in a closet.

The good:

  • Use water more efficiently than bypass
  • Can produce more humidity than bypass
  • Perfect for smaller spaces
  • Costs of running fan can be offset by turning down the thermostat in a home with proper humidity
  • Can be used when the furnace is off

The bad:

  • Cost more initially
  • Fan means higher operating costs
  • Not as easy to install as bypass
  • Still produces waste water

There are some undeniable benefits to whole-home humidification, but unfortunately, there is often a trade-off. Better humidifying means extra power is needed, and saving water means more frequent cleaning.