Cooling Load Calculations for Warehouses

Warehouse cooling design requires precise engineering because industrial buildings have large air volumes, varied occupancy, high ceilings, and dynamic thermal behaviour. Calculating the cooling load is the foundation of any HVAC design. A miscalculation leads to uneven temperatures, oversized equipment, excessive energy consumption, and poor system performance.

This article outlines the engineering methodology for calculating cooling loads in UK warehouses, including heat gains, solar load, infiltration, equipment heat output, diversity factors and stratification effects.

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1. Sensible and Latent Cooling Loads

Warehouse cooling loads consist of:

• Sensible heat (temperature increase)

• Latent heat (humidity / moisture load)

Latent load is especially relevant for:

• food storage

• pharmaceutical warehousing

• high-humidity environments

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2. Internal Heat Gains

Internal loads include:

Equipment Heat Load

Forklifts, conveyors, packaging lines, robotics and lighting all generate heat.

Typical values:

• LED lighting: 8–12 W/m²

• conveyors: 300–800 W per zone

• forklifts (electric): heat output proportional to charging cycles

Occupancy Load

Often low, but significant in packing areas.

• 75–120 W per person (sensible)

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3. Solar Heat Gain

Large warehouse roofs and walls absorb significant solar energy.

Engineering calculations use:

• roof material U-value

• solar absorption coefficient

• roof orientation

• surface area exposed

South-facing walls contribute disproportionately to afternoon heat loads.

Solar gain may represent 30–40% of the total cooling load in summer.

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4. Infiltration & Air Leakage

Warehouses have:

• loading bay doors

• dock shelters

• shutter doors

• vehicle traffic

Infiltration is calculated using:

• air change rates

• door opening frequency

• indoor–outdoor temperature difference

• stack effect

A typical infiltration load for warehouses ranges between 0.5–3 ACH depending on tightness.

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5. Stratification Effects

Stratification causes hot air to accumulate near the roof.

However, when cooling is required, stratification reduces cooling efficiency because:

• warm air descends when fans activate

• supply air mixes with hot layers

• cooling load increases during destratification

CFD analysis helps predict airflow behaviour in high-ceiling environments.

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6. Heat Transfer Through Building Envelope

The warehouse envelope is calculated using:

• U-values

• thermal bridging

• insulation level

• orientation

• surface area

Cooling load = U × Area × ΔT

Where ΔT may reach 10–15°C between indoor and peak outdoor temperatures.

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7. Diversity & Load Profiles

Warehouses rarely operate at full load continuously.

Engineers apply:

• diversity factors

• operational schedules

• equipment usage cycles

• shift patterns

These factors allow more accurate sizing and prevent overspecification.

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8. HVAC Equipment Selection

Cooling solutions include:

• VRF/VRV systems (Daikin, Mitsubishi Electric)

• large ducted systems

• chilled water AHUs

• evaporative cooling (specific applications)

Selection depends on:

• cooling load

• zoning requirements

• air volume

• humidity constraints

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Conclusion

Cooling load calculation for warehouses is a technical process that integrates solar gain, equipment heat, infiltration, stratification, and envelope performance. Proper engineering ensures accurate sizing, stable temperatures, and efficient operation — essential for industrial environments with demanding thermal requirements.