Structural Drying Equipment Needs Estimator
Estimates the number of air movers and dehumidifiers required to dry a water-damaged structure based on affected square footage, material types, saturation class, and ambient conditions.
Formulas Used
Air Movers:
Air Movers = ⌈(Floor Area + Wall Area × 0.5) × Carpet Factor / Coverage per Unit⌉
Coverage per unit: Class 1 = 16 sq ft, Class 2 = 10 sq ft, Class 3 = 8 sq ft, Class 4 = 6 sq ft (IICRC S500).
Carpet factor = 1.25 if carpet/pad present.
Dehumidifiers:
GPP = W × 7000, where W = 0.62198 × φ·Pws / (P − φ·Pws)
Pws = saturation pressure (Antoine approximation), φ = RH fraction, P = 14.696 psia
Total Grains = Volume × Air Density × (GPP_current − GPP_target@40%)
Pints/Day = (Total Grains / 3 days) / 7000 / 1.04 × Class Load Factor + Wall Load + Carpet Load
Dehumidifiers = ⌈Pints/Day / 150⌉ (LGR unit = 150 pints/day capacity)
Air Scrubbers (Cat 2/3): 1 per 1,000 sq ft (Cat 2) or 1 per 500 sq ft (Cat 3).
Negative Air Machines (Cat 3): 1 per 1,000 sq ft.
Estimated Drying Time: Base days by class (1→2d, 2→3d, 3→5d, 4→7d), extended for RH >80%/90% and temperature outside 70–95°F range.
Assumptions & References
- Based on IICRC S500 Standard for Professional Water Damage Restoration (5th Edition).
- LGR (Low Grain Refrigerant) dehumidifiers rated at 150 pints/day under restoration conditions.
- Target drying goal: ≤40% relative humidity and equilibrium moisture content (EMC) in structural materials.
- Air density approximated at 0.075 lb/cu ft, adjusted for ambient temperature.
- Saturation pressure calculated using Antoine/Magnus approximation; results within ±3% of psychrometric tables.
- Structural moisture load factors (Class 1–4) derived from IICRC S500 Table 3-1 evaporation rate guidelines.
- Power estimates: air mover ≈ 720W, LGR dehumidifier ≈ 900W, air scrubber ≈ 200W, negative air machine ≈ 750W.
- Drying time estimates assume continuous equipment operation and daily psychrometric monitoring.
- Category 2 and 3 water damage may require additional remediation steps beyond equipment placement.
- This tool provides estimates only. A certified water damage restoration professional (WRT/AMRT) should verify all equipment placement.