Cannabis Cultivation Room Special HVAC / AHU Design (Integrated Cooling+Dehumid+Reheat+Filtration+Odor Control)

1. Standard Target Parameters by Growth Stage (Core Design Basis)

Key: Flower room needs massive latent dehumid load (biggest design difficulty), avoid bud mold & mildew

2. Load Calculation Rule (Cannabis HVAC ≈3~4X cooling tonnage vs normal commercial A/C)

2.1 Sensible Heat Source (Cooling load)

LED lamp: 30~40% input power convert to heat; HPS lamp:60~70% power to heat

Veg:20~30W/㎡ LED; Flower:35~50W/㎡ LED (industry standard layout)

Pump, circulation fan, CO₂ generator, wall envelope heat gain

2.2 Latent Load (Dehumid core, critical)

Hydroponic: 0.8~1.0 gal water transpire/ft²/day; Soil:0.4~0.6 gal/ft²/day

Convert to dehumid capacity: 8pint/gal; add +20% safety margin for sealed CO₂ room

Quick budget sizing:

Veg room LED → 1RT/10~13㎡; Flower room LED →1RT/5.5~8.5㎡

3. Special Structure of Cannabis Grow Room AHU (6 Core Functional Sections)

① Multi-stage Filtration + Odor Elimination Section (unique for cannabis)

G4 pre-filter → F8 medium filter → Activated Carbon Filter / Zeolite filter (odor removal, mandatory for legal certification)

Optional: UV germicidal lamp behind filter to kill mold spore & airborne pathogen, reduce crop disease

② Cooling Coil + Hot Gas Bypass Reheat System (Most Important Component)

Big oversized evaporator coil for deep dew-point dehumid (lower coil temp to condense massive plant transpiration moisture)

Built-in compressor hot-gas reheat (no extra electric heater, save power)：After air dehumidified & over-cooled, use waste hot refrigerant gas to reheat air back to set temp → stable RH & VPD without extra power consumption

Ordinary split AC can’t do independent temp & RH control, only integrated hot-gas bypass AHU fits grow room

③ Humidifier (for clone/veg high RH requirement)

Electrode / ultrasonic humidifier, auto linkage with RH probe, used when room RH drops below set value

④ EC Variable Speed Fan

Air exchange rate: 60~120 times/h air change (1~2ACH per minute); full canopy uniform airflow, eliminate dead-air & mold spot

EC fan with 0~100% speed regulation, match light ON/OFF load variation

⑤ Fresh Air/Exhaust Dampers + Pressure Control

Sealed grow room keep slight positive pressure (+5~10Pa): prevent external pest/mold air infiltration; fresh air proportion 5~15% adjustable, match CO₂ consumption

Sealed room with CO₂ enrichment (1200ppm) needs minimal fresh air to avoid CO₂ loss

⑥ Intelligent PLC Control System

Real-time monitor: Temp, RH, VPD, CO₂, room pressure, supply/return air parameter

Auto switch mode by lighting schedule: Day mode (light ON high load) / Night mode (light OFF low load)

Remote Modbus/APP monitoring, alarm for over-humidity/over-temp (prevent flower mold loss)

4. Two mainstream Unit Types for Selection

Option1: Ducted Central AHU (Large commercial grow room >50㎡, multi-zone split veg/flower room)

Outdoor air-cooled condenser + indoor cabinet AHU + duct distribution

Centralized control, easy heat recovery, lower operation cost for big factory

Option2: Packaged Floor/Wall Mount Grow Unit (Small/medium room <50㎡, plug&play)

All-in-one cabinet (condenser+evap inside unit), duct air supply, no separate outdoor unit, convenient for container grow room

5. Anti-corrosion & Material Upgrade (High humidity + organic volatile air inside grow room)

Internal casing: galvanized steel + epoxy coating / optional 304SS

Drain pan: full 304 stainless steel (prevent organic condensate corrosion & algae block drain)

Coil fin: hydrophilic epoxy coated aluminum fin, anti-mold & corrosion in high humid air

6. Extra Auxiliary System Matching

In-room HAF oscillating canopy fans: make micro-airflow around leaves, boost transpiration & CO₂ absorption

Waste heat recovery optional: recycle condenser heat for winter room heating to cut running cost