What is the maximum winter humidity design for an inside temperature of 72°F when the outside temperature is 10°F?

To determine the maximum winter humidity design for the specified indoor and outdoor temperatures, the concept of the dew point and the relationship between temperature and relative humidity must be considered. The maximum humidity level indoors is not just a straightforward number, as it depends on the capacity of the air to hold moisture at the given temperature.

At an indoor temperature of 72°F and an outdoor temperature of 10°F, the air outside is much colder, which significantly reduces its capacity to hold moisture compared to the warmer air inside. To find a practical and safe level of relative humidity for winter indoor settings, it is important to avoid condensation that can occur if the indoor humidity is too high when cold air comes in from outside.

Generally, as the temperature decreases, the air’s ability to hold moisture decreases, which means that at colder temperatures, the relative humidity must also be lower to prevent condensation. The maximum recommended indoor relative humidity under these specific temperature conditions is typically around 30%. This is considered a safe upper limit to prevent condensation on windows and other cold surfaces, which can lead to moisture problems and mold growth.

Therefore, the value of 30% RH is appropriate, as it provides a balance between comfort and safety in winter conditions without risking condensation issues.