What size commercial AC do you need for a 20,000 sq ft Warehouse? A warehouse of this size carries a low internal heat load (large volume with light occupancy), so it typically needs about 38.2 tons of cooling — best installed as 3 × 15-Ton RTUs for redundancy — plus about 1,800 CFM of fresh air (ASHRAE 62.1). The calculator below is pre-set to this space.
Commercial Cooling Loads for a Warehouse
Sizing an air conditioning system for a Warehouse is drastically different from residential Manual J calculations. A Warehouse introduces specific, high-intensity internal heat gains—from specialized equipment, concentrated lighting, changing occupancy densities, and strict ventilation codes requiring fresh outside air. You cannot use a generic square-footage rule of thumb. Use the commercial calculator below to account for these heavy sensible and latent heat loads to ensure your facility maintains a comfortable, safe, and code-compliant environment.
🏢 Commercial Cooling Tonnage, RTU Staging & CFM
Size commercial HVAC for offices, retail, restaurants, server rooms and warehouses. Get the required cooling tonnage, a recommended rooftop unit (RTU) staging combination, and the fresh-air ventilation CFM — factoring business type, occupancy, internal heat loads, ceilings and climate.
🏢1. Building Type
Each building type carries a different internal heat load — a restaurant kitchen or server room runs far hotter than an office or warehouse.
📐2. Floor Area & Ceiling
Range: 500 – 50,000 sq ft
👥3. Occupancy & Internal Loads
Auto-set from building type & area — adjust to your peak headcount.
🌍4. Climate & Unit Staging
Multiple staged RTUs give redundancy (if one fails, the building stays partly cooled) and better part-load efficiency — the commercial standard.
20,000 Sq Ft Warehouse Cooling Load by Climate
The same 20,000 sq ft Warehouse needs more cooling in a hotter climate. Recommended tonnage and RTU staging:
| Climate | Cooling Load | Recommended RTUs |
|---|---|---|
| Northern / Mild | 38.2 tons | 3 × 15-Ton RTUs |
| Humid South | 42.0 tons | 3 × 15-Ton RTUs |
| Sunbelt / Desert | 43.9 tons | 3 × 15-Ton RTUs |
Why a 20,000 Sq Ft Warehouse Needs 38.2 Tons
Commercial cooling load comes from four sources: the building envelope (20,000 sq ft × a per-square-foot factor × ceiling height), occupancy (about 40 people here at 400 BTU/hr each), equipment & lighting, and sun/climate. For a warehouse, the low internal load from large volume with light occupancy is the deciding factor — which is why it needs far less cooling than an office of the same size. Commercial installs almost always use staged rooftop units (3 × 15-Ton RTUs) so the building stays partly cooled if one unit fails. Fresh-air ventilation adds 1,800 CFM (ASHRAE 62.1), and total supply airflow is about 15,264 CFM.
Frequently Asked Questions
What size AC does a 20,000 sq ft Warehouse need? About 38.2 tons of cooling in a moderate climate — roughly 524 sq ft per ton — typically installed as 3 × 15-Ton RTUs. Hotter climates push this higher.
How many rooftop units for a 20,000 sq ft Warehouse? We recommend 3 × 15-Ton RTUs (45 tons installed). Multiple staged RTUs give redundancy and better part-load efficiency than one large unit.
How much fresh air (CFM) does a 20,000 sq ft Warehouse need? About 1,800 CFM of outdoor air under ASHRAE 62.1, based on ~40 occupants plus floor area. Total supply airflow is around 15,264 CFM.
Related: the fundamentals of industrial refrigeration.
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Figures are reviewed by the Refcon HVAC engineering team using U.S. DOE, ENERGY STAR & ACCA Manual J data. Estimates only — confirm with a licensed pro.