Introduction to Cooling Load Calculation
The cooling load is the amount of heat that must be removed from a conditioned space to maintain the design temperature. Properly designed air conditioning systems rely on accurate calculations that avoid oversizing or undersizing.
Components of the Cooling Load
A. External Loads
- Solar radiation heat through walls and roofs (Wall/Roof Conduction)
- Solar radiation heat through windows (Solar Heat Gain)
- Infiltration heat
B. Internal Loads
- People heat: 75 W sensible + 55 W latent per person (office activity)
- Lighting heat: 3.5 – 12 W/m² depending on type
- Electrical equipment heat
Wall and Roof Load Equation (CLTD)
Q = U × A × CLTD_corrected
Where: U = thermal transmittance coefficient (W/m²·K), A = area (m²), CLTD = corrected cooling load temperature difference for design
| Building Element | U (W/m²K) | Note |
|---|---|---|
| Concrete wall 20cm | 1.5 – 2.0 | Depends on insulation |
| Insulated roof | 0.3 – 0.5 | 10cm XPS insulation |
| Double Low-E glazing | 1.8 – 2.2 | SHGC ≤ 0.25 |
