What pressure condition is typically used when dehumidifying a building in a hot and humid climate?

• A. Negative pressure
• B. Positive pressure
• C. Atmospheric pressure
• D. Zero pressure differential

Answer: (B)

A slight positive pressure inside the building helps prevent outdoor humidity from infiltrating. When the indoor air is at a higher pressure than outdoor air, air leaks move outward through cracks and joints rather than letting humid outdoor air seep in, which reduces the latent moisture load the dehumidification system must remove. In hot and humid climates, outdoor air carries a lot of moisture, so keeping the indoors slightly pressurized makes humidity control more effective and energy-efficient. Negative pressure would pull in humid outdoor air, worsening humidity control. Neutral or zero differential offers no protection against moisture entering through leaks. Therefore, maintaining a modest positive pressure is the typical approach.