Cooling Load Calculator estimates the cooling requirements of a space using either a quick area-based method or a more detailed ΔT + ventilation method. It helps HVAC designers and architects size air conditioning systems during early design stages.
About cooling load. Cooling load is the amount of heat that must be removed from a space to maintain comfortable indoor conditions. It comes from heat transfer through walls, roofs, and windows, as well as from ventilation, solar gains, lighting, equipment, and occupants. Accurately estimating it is crucial for sizing air conditioning systems.
About the area intensity method. This method uses a typical cooling load intensity (CLI) in watts per square meter (W/m²) or BTU per hour per square foot (BTU/h·ft²). It gives quick early-stage estimates by multiplying area by intensity and internal gains, then adding heat from occupants.
About the ΔT + ventilation method. This method calculates cooling load from the building’s heat gain through the envelope and from ventilation. It uses U·A per area (W/m²·K), indoor-outdoor temperature difference (ΔT), air changes per hour (ACH), and ceiling height to estimate sensible heat gains, and adds internal and occupant gains.
About internal gains and occupants. Internal gains are the heat contributions from lighting, appliances, and equipment, typically in W/m². People also give off sensible heat, assumed here as 75 W per person as a rule of thumb. These values are added to the cooling load.
Calculation. The calculator offers two workflows:
Area Intensity method: Q = A × (CLI + IG) + (P × 75)
ΔT + Ventilation method: Q = A × UA × ΔT + 0.33 × ACH × (A × H) × ΔT + (A × IG + P × 75)
- Example 1 (Area method): A = 120 m², CLI = 100 W/m², IG = 12 W/m², P = 4 → 120×(100+12)+4×75 ≈ 13.74 kW.
- Example 2 (ΔT method): A = 200 m², UA = 1.2 W/m²·K, ΔT = 10 °C, ACH = 1.5, H = 2.7 m, IG = 12 W/m², P = 4 → ≈ 18.3 kW.
- Example 3 (Imperial): A = 1292 ft², CLI = 32 BTU/h·ft², IG = 3 BTU/h·ft², P = 4 → ≈ 46,800 BTU/h.
Corresponding tools. Use the Heating Load Calculator to size heating systems, the CFM Calculator to determine ventilation airflow, and the Duct Sizing Calculator to dimension ducts based on airflow.
