What is the typical problem with systems that lack humidification in winter?

• A. They may experience unacceptably low indoor relative humidity.
• B. They may experience excess condensation on windows.
• C. They may overheat the space.
• D. They may have excessive indoor CO2.

Answer: (A)

In winter, outdoor air is cold and holds little moisture, and many systems condition or ventilate this air without adding humidity. Without humidification, indoor relative humidity tends to fall well below comfortable levels (often below 30%). Low humidity can cause dry skin and eyes, throat irritation, and discomfort, and it can affect building materials and overall occupant well-being. Condensation on windows happens when humidity is high enough to reach the dew point on cold surfaces, so a dry indoor environment makes window condensation unlikely. Overheating isn’t a typical direct consequence of missing humidification, and CO2 levels relate more to ventilation rates than to humidity. So the typical problem is unacceptably low indoor relative humidity.