The optimal humidity level for a home or building depends on various factors, including the outdoor climate, indoor activities, and occupant comfort. A general rule of thumb is to maintain a relative humidity (RH) between 30% and 60%. However, this can vary depending on the specific circumstances. For example, in colder climates, a lower RH may be necessary to prevent condensation, while in hotter climates, a higher RH may be required to maintain comfort.