Sizing commercial AC in Illinois? Illinois’s moderate Northern climate means commercial cooling loads run at the standard baseline. A typical 3,000 sq ft office in Illinois needs about 9.2 tons (2 × 5-Ton RTUs). The calculator below is pre-set to Illinois’s climate — pick your building type and size.
Commercial Cooling Loads for a Commercial Facility
Sizing an air conditioning system for a Commercial Facility is drastically different from residential Manual J calculations. A Commercial Facility 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.
Commercial AC Size in Illinois by Business Type
Typical cooling load and RTU staging for common commercial spaces at Illinois’s climate:
| Business (size) | Cooling Load | Recommended RTUs |
|---|---|---|
| Office (3,000 sq ft) | 9.2 tons | 2 × 5-Ton RTUs |
| Retail (3,000 sq ft) | 13.1 tons | 2 × 7.5-Ton RTUs |
| Restaurant (2,000 sq ft) | 13.8 tons | 2 × 7.5-Ton RTUs |
| Server room (1,000 sq ft) | 7.1 tons | 1 × 7.5-Ton RTU |
| Warehouse (10,000 sq ft) | 19.1 tons | 2 × 10-Ton RTUs |
Sizing Commercial AC for Illinois’s Climate
Because Illinois has a moderate Northern climate, rooftop units here should be sized to the standard load, with the heating side mattering more in winter. Business type still drives the number most — a restaurant or server room needs several times the tonnage of a warehouse of the same size. Stage multiple RTUs for redundancy, and have a licensed Illinois mechanical engineer produce the stamped design.
Frequently Asked Questions
How much commercial AC do I need in Illinois? A 3,000 sq ft office in Illinois needs about 9.2 tons; a 2,000 sq ft restaurant about 13.8 tons. Illinois’s moderate Northern climate keeps loads at the baseline.
Does Illinois’s climate change commercial AC sizing? Yes — the moderate climate keeps loads at the national baseline. Business type and size still matter most.
Do I need a permit and engineer for commercial AC in Illinois? Yes. Commercial HVAC in Illinois requires a stamped mechanical design and permits. Use this tool to scope and budget, then hire a licensed local engineer and contractor.
Background: how industrial refrigeration systems are built.
Estimates vary by contractor. Compare free quotes from licensed local pros before you commit. Request a quote →
High-efficiency systems may qualify for utility rebates and federal or state incentives. Find current programs at ENERGY STAR & DSIRE.
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.