What is the design limit for relative humidity in occupied spaces?

• A. 65%
• B. 55%
• C. 60%
• D. 70%

Answer: (A)

The design limit for relative humidity in occupied spaces is sixty-five percent. This ceiling provides a practical balance: it helps prevent condensation on cooler surfaces during humid periods and reduces the risk of mold and material damage, while still keeping humidity high enough for occupant comfort and to avoid overly dry conditions. A higher limit, like seventy percent, would raise condensation and mold risk and increase dehumidification energy, while lower values such as fifty-five or sixty percent are more conservative but not the standard design cap.