Thermal
Latent Load
The portion of a cooling load that comes from removing moisture rather than lowering temperature. In humid climates it can rival the sensible load, and equipment sized only for temperature will not meet it.
In more detail
A cooling load has two parts. The sensible load is the heat that changes air temperature. The latent load is the energy required to remove moisture — the heat released when water vapor condenses on a cooling coil. Together they are the total load, and their ratio is the sensible heat ratio.
Latent load comes from outdoor air brought in by ventilation and infiltration, from occupants, and from cooking, showering, laundry and plants. In a humid climate, ventilation air is often the largest single contributor, and it grows as a share of the total in a well-insulated house whose sensible load has been reduced. A tight, well-shaded house in Houston can have a latent fraction high enough that equipment selected on total capacity alone will hold temperature and fail on humidity.
Equipment is characterized by its split. A unit with a high sensible heat ratio removes little moisture per unit of cooling; a lower ratio removes more. Manual J calculations produce sensible and latent figures separately, and selecting against the total while ignoring the split is where most residential humidity problems originate.
Why it matters
Latent load is why a house can be cold and clammy at once, and why the honest answer to a new efficient house feeling humid is usually a load calculation that addressed temperature and not moisture. It also determines whether dedicated dehumidification is needed — a mechanical design decision with space, drain and duct implications, rather than an appliance purchase made later.
The common misunderstanding
That a larger air conditioner will fix humidity. Oversized equipment reaches the temperature setpoint faster and runs less, which removes less moisture — the opposite of the intent. Matching the equipment's sensible-to-latent split to the calculated loads, and adding dedicated dehumidification where that split cannot be met, is what addresses it.
Related terms
On Compound
Where this term does real work — and where the decisions get made.
Sources
Last reviewed July 2026 by Compound Editorial. Definitions are educational and not project-specific engineering or medical advice.