Find the right whole-house humidifier capacity for your home in gallons per day (GPD), based on square footage, ceiling height, and how tight or drafty your home construction is — the same sizing standard AprilAire publishes for its whole-house humidifiers.
sq ft
ft
Loose: older home, visible gaps, noticeable drafts. Average: typical construction, standard windows and insulation. Tight: newer or recently sealed/insulated home with modern windows — needs less GPD for the same square footage since less humidified air escapes.
Humidifier output you need
17GPD
Achievable with a standard whole-house humidifier
Square footage
2,000 sq ft
Construction
Average
Adjustments
None
Real humidifiers that clear this GPD rating
Formula: base GPD requirement comes from AprilAire's published Whole-House Humidifier Specifications (Form No. 222), which rate coverage at 750/1,500/3,000 sq ft (loose/average/tight construction) for a 12 GPD unit, scaling up to 1,050/2,100/4,200 sq ft for an 18 GPD unit, assuming 8 ft ceilings. We convert that into
GPD = 0.005 × (sq ft × construction multiplier) − 3, where the multiplier is 4 for loose, 2 for average, or 1 for tight construction — then scale by Ceiling Height ÷ 8, and add 15% for very cold/dry winter climates (design temp below 10°F), since AprilAire's own chart assumes a 20°F outdoor design temperature.
