What to do when humidity is stuck

Indoor humidity outside the 30 to 50% range produces real consequences: below 30% means dry mucous membranes, higher viral survival, and irritation; above 60% means mold risk and dust-mite habitat (see humidity). When the dashboard reports humidity stuck outside the comfort range, four diagnostic paths cover almost all cases.

Work the paths in order; each lists how to recognize it and what to do.

1. Outdoor air dominance. In humid summer climates, outdoor dew point may exceed indoor by 5 to 15 °C; opening windows or running fresh-air mode imports the humidity. Diagnosis: indoor humidity tracks outdoor dew point; humidity drops when HVAC runs in cooling-only mode. Action: run AC (which dehumidifies as a side effect) or a standalone dehumidifier. In dry winter climates the inverse holds: outdoor air is desiccating and indoor humidity drops with ventilation, so humidify and do not over-ventilate.
2. Internal water source. A slow plumbing leak, a malfunctioning toilet, a basement water intrusion, or chronic shower-fan failure. Diagnosis: humidity elevated continuously, often localized to one area, may correlate with VOC elevation from mold. Action: visual inspection, then plumber.
3. HVAC failure. AC condensate drain blocked, dehumidifier failed, HRV core fouled. Diagnosis: humidity correlates with HVAC operation in an unexpected direction. Action: HVAC service.
4. Seasonal mismatch. Cold-zone winter homes routinely drop below 25% RH because cold outdoor air holds less water and indoor heating evaporates moisture from materials. Diagnosis: humidity drops sharply each winter, recovers in spring; see seasonal IAQ shifts and climate zone effects. Action: portable or whole-home humidifier; target 35-40% in winter, lower in zones where higher humidity would condense on cold walls (mold risk).

The dashboard's climate-zone-aware target lowers the upper bound in cold-climate winters to balance humidity against condensation.