Which item is NOT a component of the typical moisture load formula for humidification?

Which item is NOT a component of the typical moisture load formula for humidification?

• A. Outdoor temperature difference
• B. Space gains
• C. Infiltration rate
• D. Ventilation rate

Answer: (A)

In humidification design, the latent moisture load comes from two main sources: moisture added by outdoor air entering the space (through ventilation and infiltration) and moisture generated inside the space itself (space gains from occupants, processes, etc.). The calculation uses the rate of outdoor air and the difference in humidity ratio between outdoor and indoor air to quantify how much water the entering air brings in or removes. This makes the humidity content, not the air temperature, the critical factor. Outdoor temperature difference by itself does not appear in the typical moisture load formula because it does not directly quantify how much moisture is carried by the air. Two air streams can have very different water content even at similar or different temperatures, and what matters for latent load is the humidity ratio difference and the air exchange rate. Therefore, the item that is not a component of the standard moisture load formula is the outdoor temperature difference. The other items—space gains, infiltration rate, and ventilation rate—are all linked to moisture sources or exchanges that affect the latent load.

In humidification design, the latent moisture load comes from two main sources: moisture added by outdoor air entering the space (through ventilation and infiltration) and moisture generated inside the space itself (space gains from occupants, processes, etc.). The calculation uses the rate of outdoor air and the difference in humidity ratio between outdoor and indoor air to quantify how much water the entering air brings in or removes. This makes the humidity content, not the air temperature, the critical factor.

Outdoor temperature difference by itself does not appear in the typical moisture load formula because it does not directly quantify how much moisture is carried by the air. Two air streams can have very different water content even at similar or different temperatures, and what matters for latent load is the humidity ratio difference and the air exchange rate. Therefore, the item that is not a component of the standard moisture load formula is the outdoor temperature difference. The other items—space gains, infiltration rate, and ventilation rate—are all linked to moisture sources or exchanges that affect the latent load.