Sizing an industrial dehumidifier for a warehouse is an engineering exercise that must account for moisture load, not just floor area. Oversizing increases capital and energy costs; undersizing leads to persistent condensation, corrosion, and mold risk.

 

1. Define the Design Conditions

Indoor Target Conditions

Temperature: typically 15–25 °C (59–77 °F)

Relative Humidity:

General storage: 45–60% RH

Corrosion-sensitive goods/packaging: 40–50% RH

Cold or unheated warehouses: dew point–based control is preferred

Outdoor Design Conditions

Use local summer design conditions (worst-case moisture load), not annual averages.

 

2. Calculate Warehouse Volume

Volume (ft³)=Area (ft²)×Clear Height (ft)

Example:
50,000 ft² × 30 ft = 1,500,000 ft³

Volume is critical for air circulation and infiltration calculations.

 

3. Identify Moisture Load Sources

Industrial dehumidifiers are sized based on total moisture load (lb/hr or kg/hr).

(1) Air Infiltration Load

Moist outside air entering through:

Dock doors

Truck bays

Personnel doors

Poor building envelope

Typical infiltration assumptions:

0.2–0.5 ACH (tight warehouse)

0.5–1.5 ACH (frequent door openings)

Moisture load formula:
Moisture Load (lb/hr)=4.5×CFM×(W_out−W_in)

Where W = humidity ratio (lb moisture/lb dry air)

 

(2) Internal Moisture Generation

Include:

Wet products or pallets

Wash-down processes

Forklift combustion (LP gas)

Workers (≈ 0.2–0.3 lb/hr/person)

 

(3) Structural Moisture

Concrete slab evaporation (new buildings)

Roof or wall vapor diffusion

Uninsulated metal walls

 

4. Convert Moisture Load to Dehumidifier Capacity

Capacity Units

Pints/day (PPD) – North America

Liters/day (LPD) – International

kg/hr or lb/hr – Engineering standard

Conversion:

1 lb/hr ≈ 12 pints/day

1 kg/hr ≈ 24 liters/day

Example Calculation

If total moisture load = 35 lb/hr:
35×12=420 pints/day

Apply safety factor:

+15–25% for door activity and seasonal spikes
Final capacity ≈ 500–550 PPD

 

5. Select Dehumidifier Type

Refrigerant Dehumidifiers

Best for >10 °C (50 °F) spaces

Lower capital cost

Suitable for most general warehouses

Desiccant Dehumidifiers

Required for:

Cold or unheated warehouses

Low-RH targets (<40%)

Condensation prevention on metal surfaces

Many large warehouses use hybrid systems (refrigerant + desiccant).

 

6. Airflow and Distribution (Often Overlooked)

Dehumidification capacity is meaningless without proper air movement.

Target 3–5 air turnovers per hour

Use:

Ducted industrial dehumidifiers

Multiple distributed dehumidifiers

Avoid dead zones near walls, racks, and ceilings

 

7. Quick Rule-of-Thumb (Preliminary Only)

For warm warehouses (≥ 60 °F):

Warehouse Condition	Approx. Capacity
Light duty, low traffic	0.08–0.12 PPD/ft²
Moderate traffic	0.12–0.18 PPD/ft²
Heavy dock activity	0.18–0.25 PPD/ft²

Example:
50,000 ft² × 0.15 ≈ 7,500 PPD
(Usually split across multiple industrial units)

The rule-of-thumb must always be validated against moisture load calculations.

 

8. Common Sizing Mistakes

Sizing by floor area only

Ignoring the dock door air exchange

Using residential units in industrial spaces

No allowance for seasonal humidity peaks

Inadequate air distribution planning

 

Best Practice Summary

The selection of an industrial dehumidifier for warehouse is always sized by moisture load, not square footage

Account for infiltration + internal moisture

Choose refrigerant vs desiccant based on temperature and RH target

Add a 15–25% safety margin

Consider multiple units for redundancy and airflow coverage