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    Buildings / cooling load

    Cooling load calculator

    Cooling is two loads, not one: heat that raises the temperature and moisture that has to be condensed out. This calculator computes the psychrometric state of room and supply air, splits sensible from latent load, and reports the sensible heat ratio that decides whether the coil can hold humidity.

    ΔT10 KRoom RH50%SHR0.92
    Total cooling load
    13.08 kW
    1.00 m³/s of supply air
    Sensible
    12.07 kW
    92% of the total
    Latent
    1.01 kW
    Moisture removal
    Room dew point
    12.9 °C
    Supply 12.4 °C
    Air state
    Room and supply conditions, and the load each difference produces.
    13.08 kW
    Air state
    PropertyRoomSupply
    Dry-bulb (°C)24.014.0
    Relative humidity50%90%
    Humidity ratio (kg/kg)0.009280.00894
    Enthalpy (kJ/kg)47.836.7
    Dew point (°C)12.912.4

    Sensible load comes from ΔT; latent load comes from the humidity-ratio difference.

    Inspect the model
    Choose a quick result view, a scaled comparison, or the complete diagnostic set.
    Cooling load against supply ΔT
    Sensible load is linear in ΔT; latent load stays roughly constant.
    Cooling load against supply ΔT-16.55-8.67-0.7977.0814.9522.832233445566778899101011111212kW
    Sensible and latent
    The split determines whether a coil can hold the room humidity.
    Sensible and latent0.0002.855.708.5511.4014.2412.07SensibleSensible1.01LatentLatentkW
    Canonical equations
    The exact relationships implemented by this engine.

    Qs = 1.2 · Q · cp · ΔT · 1.2 kg/m³ is standard air density.

    Ql = 1.2 · Q · ΔW · 2501 · 2501 kJ/kg is the latent heat of vaporisation.

    Qs / (Qs + Ql) · Below about 0.75 the coil must dehumidify deliberately.

    engineering methodology

    A clear path from inputs to results.

    Cooling is two loads, not one: heat that raises the temperature and moisture that has to be condensed out. This calculator computes the psychrometric state of room and supply air, splits sensible from latent load, and reports the sensible heat ratio that decides whether the coil can hold humidity.

    Step-by-step methodWorked exampleAssumptions explained

    How to use

    1. Enter the supply airflow.
    2. Set the room dry-bulb and relative humidity.
    3. Set the supply dry-bulb and relative humidity.
    4. Read the sensible, latent and total load.

    The formula

    Qs=1.2 Q cp ΔT,Ql=1.2 Q ΔW 2501Q_s = 1.2\,Q\,c_p\,\Delta T, \qquad Q_l = 1.2\,Q\,\Delta W\,2501

    Reference: ASHRAE psychrometrics; Magnus formula for saturation pressure.

    Worked example

    1 m³/s from 14 °C to a 24 °C room at 50% RH

    Inputs
    • Supply 1 m³/s at 14 °C, 90% RH.
    • Room 24 °C, 50% RH.
    Calculation path
    1. 1

      Room humidity ratio 0.0093 kg/kg; supply 0.0090 kg/kg.

    2. 2

      Sensible: 1.2 × 1 × 1.006 × 10 × 1000 = 12.07 kW.

    3. 3

      Latent: 1.2 × 1 × 0.00034 × 2501 × 1000 = 1.01 kW.

    4. 4

      Total 13.08 kW; sensible heat ratio 0.923.

    Result

    13.08 kW total · SHR 0.923.

    Interpreting the result

    A high sensible heat ratio means most of the load is temperature, and the coil may not dehumidify enough at part load. Below about 0.75 the coil must be selected deliberately for latent capacity, which is why humidity problems appear in well-insulated buildings with oversized equipment.

    Assumptions & limitations

    • Steady-state coil load at the stated conditions.
    • Standard air density of 1.2 kg/m³.
    • No duct gains, fan heat or outside-air load.

    Frequently asked questions

    What is the sensible heat ratio?

    The fraction of the total load that changes temperature rather than moisture.

    Can I use this for a whole building?

    It sizes a coil for a given airflow, not a building. Use a room-by-room load calculation for that.

    Why does humidity matter?

    Latent load is energy used to condense water; ignoring it undersizes the coil and the room stays damp.

    Methodology last reviewed 2026-10-21. Results are informational and not financial or engineering advice — see our disclaimer.