Dehumidification Load Calculator
Calculates total dehumidification load from three sources: baseline moisture to be removed from the space volume, ventilation/infiltration ingress, and internal latent loads from occupants. Worst-case assumes indoor and outdoor humidity start at the same point.
Inputs
Indoor Temperature Target
°F
Max Outdoor Humidity (RH%)
%
Indoor Humidity Target (RH%)
%
Outdoor Temperature
°F
Indoor Volume (W × D × H)
ft³
Occupants
persons
Latent Heat per Occupant
BTU/hr (ACCA Manual J v8)
Air Changes per Hour (ACH)
ACH
ERV Efficiency (0 if no ERV)
fraction (0–1)
Intermediate Calculations
Indoor Volume
—
m³
Ventilation Flow Rate (ACH × Volume)
—
m³/hr
Ventilation Flow Rate
—
CFM
Outdoor Absolute Humidity
—
g/m³
Indoor Absolute Humidity (target)
—
g/m³
Δ Absolute Humidity (outdoor − indoor)
—
g/m³
Results
Total Pints / Day
—
pints per day
Total Pints / Hour
—
pints per hour
Total kg / Day
—
kg per day
Load Breakdown
| Load Component | kg / hr | kg / day |
|---|---|---|
| Baseline (one-time space volume recovery) | — | — |
| Ventilation / Infiltration Ingress | — | — |
| Internal Latent (occupants) | — | — |
| TOTAL | — | — |
Note: Most dehumidifier "pints per day" PPD ratings are based on AHAM standards (an Industry trade group) and are not tested at the conditions that make sense for an application such as radiant cooling. We suggest to de-rate the manufacturer supplied ratings of most brands by 20-25% from what is advertised.
Methodology: Assumed worst-case starting point — indoor and outdoor humidity are the same (max expected). There are many ways to calculate humidity removal requirements. Most online resources deal with a "one-time" removal without regard to ingress from ventilation (intentional or leakage). This calculator breaks out all three components so you can make informed decisions.
Absolute Humidity Formula: AH (g/m³) = 6.112 × e^[17.67 × T / (T + 243.5)] × RH × 2.1674 / (273.15 + T)
Latent Load: (occupants × BTU/hr) / 1049 × 453.59 / 1000 kg/hr
Ingress: ΔAH × ventilation flow × (1 − ERV efficiency)
Methodology: Assumed worst-case starting point — indoor and outdoor humidity are the same (max expected). There are many ways to calculate humidity removal requirements. Most online resources deal with a "one-time" removal without regard to ingress from ventilation (intentional or leakage). This calculator breaks out all three components so you can make informed decisions.
Absolute Humidity Formula: AH (g/m³) = 6.112 × e^[17.67 × T / (T + 243.5)] × RH × 2.1674 / (273.15 + T)
Latent Load: (occupants × BTU/hr) / 1049 × 453.59 / 1000 kg/hr
Ingress: ΔAH × ventilation flow × (1 − ERV efficiency)
