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Whole House Humidifier Sizing

The two main factors when choosing the best size of humidifier for your home are the size of the area in the home you wish to humidify, and the tightness (how well insulated) of the home. The standard output measurement for furnace humidifiers is the number of gallons of water absorbed into the air in a 24 hour period. A traditional counter top humidifier designed to provide adequate humidity for a standard sized room will usually hold about one or two gallons of water. A stand-alone humidifier that is intended to humidify an entire home will either have to be attached to a sink, have a 10 - 12 gallon water reservoir, or require numerous refillings during the day and night.

All high end furnace humidifiers will have a direct water line that will provide the humidifier with a constant source of water. In order to determine the size of humidifier needed for your home, consult the chart below.

How Much Humidity Do You Need?
Tight Home
Well insulated, vapor barrier, tight storm doors and windows with weather-stripping, dampened fireplace.
Size of Home 500 Sq. Ft. 1,000 Sq. Ft. 1,500 Sq. Ft. 2,000 Sq. Ft. 2,500 Sq. Ft. 3,000 Sq. Ft.
Gallons per day required * 1.4 gpd 3.2 gpd 4.9 gpd 6.6 gpd 8.3 gpd
Average Home
Insulated, vapor barrier, loose storm doors and windows, dampened fireplace.
Size of Home 500 Sq. Ft. 1,000 Sq. Ft. 1,500 Sq. Ft. 2,000 Sq. Ft. 2,500 Sq. Ft. 3,000 Sq. Ft.
Gallons per day required 0.5 gpd 3.0 gpd 5.5 gpd 8.0 gpd 10.5 gpd 13.0 gpd
Loose Home
Little insulation, no storm windows or doors, no vapor barrier, undampened fireplace.
Size of Home 500 Sq. Ft. 1,000 Sq. Ft. 1,500 Sq. Ft. 2,000 Sq. Ft. 2,500 Sq. Ft. 3,000 Sq. Ft.
Gallons per day required 1.0 gpd 4.0 gpd 7.0 gpd 10.0 gpd 13.1 gpd 16.1 gpd
* Humidification not necessary to maintain conditions of 70 degrees F and 30% relative humidity.