Structural Drying Equipment Placement Calculator
Calculate the number of air movers and dehumidifiers required for structural drying based on IICRC S500 standards, affected area, and moisture conditions.
Formulas Used
Air Movers:
Air Movers = ⌈Floor Area × Class Density⌉ + ⌈(Perimeter × Wall Fraction) ÷ 16⌉ + Ceiling Movers
Class Density: Class 1 = 0.010, Class 2 = 0.015, Class 3 = 0.020, Class 4 = 0.025 movers/ft²
Moisture Load (pints/day):
Load = Volume (ft³) × Class Evaporation Factor × (GPP Differential ÷ 100 + 1) × Surfaces Factor × Temp Factor
Class Evap Factors: Class 1 = 0.00040, Class 2 = 0.00080, Class 3 = 0.00120, Class 4 = 0.00160
Surfaces Factor = 1 + (Surfaces − 1) × 0.15 | Temp Factor: ≥70°F = 1.0, 60–69°F = 0.85, <60°F = 0.70
Dehumidifiers:
Adjusted Capacity = 150 pints/day × Temp Factor × (Indoor GPP ÷ 100)
Dehumidifiers = ⌈Moisture Load ÷ Adjusted Capacity⌉
Air Changes Per Hour (ACH):
ACH = (Air Movers × 300 CFM × 60 min) ÷ Volume (ft³) | Target: ≥ 4 ACH
Assumptions & References
- Based on IICRC S500 Standard for Professional Water Damage Restoration (5th Edition).
- Each air mover is assumed to deliver approximately 300 CFM at operating conditions.
- LGR dehumidifiers rated at 150 pints/day under AHAM standard conditions (80°F, 60% RH); adjusted for actual temperature and humidity.
- Target indoor GPP for structural drying: 50 GPP (≈ 40% RH at 70°F).
- Wall mover spacing based on 1 air mover per 16 linear feet of affected wall (IICRC guideline).
- Class 4 drying (hardwood, concrete, plaster) may require desiccant dehumidifiers and supplemental heat not fully captured by this calculator.
- GPP values should be obtained from a calibrated psychrometer or thermo-hygrometer; use psychrometric charts for conversion from RH.
- This calculator provides estimates only. A certified water damage restoration professional (WRT/ASD) should verify equipment placement on-site.