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Latent Energy Load Moisture Removal or Addition Calculator

Heat Transfer Engineering
HVAC Design and Engineering

Moisture Removal or Addition by HVAC Latent Energy Load Calculator

HVAC air exchange modifies the moisture content of air in a building. The rate of energy consumption associated with these latent loads, to add or remove water from the air and neglecting the energy associated with any condensate, is

Eq. 1
ql = 60 · Q · ρ · ΔW ( 1061 +0.444T)


ql = latent heat load to remove or add moisture, Btu/h
Q = airflow rate, cfm
ρ = air density, lbm/ft3 (about 0.075 at or near sea level)
ΔW = humidity ratio difference between indoors and outdoors, lbm water/lbm dry air (lbmw/lbmda)
ΔT = average of indoors and outdoor temperature, °F

Equation (1) is known as the latent heat equation. When at or near sea level, and for common comfort air temperatures, the right hand side of Equation is approximately

Eq. 2
ql = 4840QΔW



ASHRAE Handbook - HVAC Handbook Fundamentals, ASHRAE: 2021, page 16.12