Preliminary HVAC Cooling Load & Tonnage Screening Estimator
Calculates sensible and latent heat gains (building envelope transmission, solar fenestration, occupants, equipment, and ventilation air), decoupled base/design BTU/h, commercial tonnage (TR), and circulating airflow (CFM).
Engineering Screening Methodology & Assumptions
Default Screening Assumptions
This tool provides rapid preliminary screening and equipment capacity estimation. The following parameters represent default screening assumptions, not rigid ASHRAE standard mandates:
- Envelope transmission: 32.0 BTU/h·ft² carpet area.
- Solar fenestration: 75.0 BTU/h·ft² glass exposure.
- Occupants: 450 BTU/h per person (250 sensible + 200 latent).
- Fresh air ventilation: 15 CFM/person (ΔT = 25°F, ΔW = 0.007 lb/lb).
- Airflow sizing factor: 400 CFM per Ton of Refrigeration (TR).
Contrast with Full ASHRAE Design
A formal ASHRAE cooling load calculation requires the Radiant Time Series (RTS) or Heat Balance (HB) method per ASHRAE Handbook - Fundamentals (Chapters 17 & 18) with hourly solar angle radiation, dimensionless Solar Heat Gain Coefficients (SHGC), composite multi-layer wall/roof U-factors, thermal storage factors, and ASHRAE Standard 62.1 ventilation schedules.
q_design = q_base × Safety_Margin
Tonnage (TR) = q_design / 12,000 BTU/h
Airflow (CFM) = Tonnage × 400 CFM/TR
This calculation provides preliminary engineering screening and feasibility sizing. Project-specific chiller, VRF, or package unit procurement requires detailed room-by-room solar heat balance modeling, building orientation analysis, envelope U-factor verification, and psychrometric coil selection verified by a certified MEP consultant.