Relative humidity describes how close air is to saturation at its current temperature. As temperature changes, the same moisture load can produce a different relative-humidity percentage. This is why an indoor percentage and an outdoor percentage are not directly comparable on their own.
Vapour pressure provides a more comparable estimate of how much moisture is in the air. Looking at the indoor-outdoor difference can help indicate whether bringing in outdoor air for a short period is likely to support drying.
A short rise after bathing or cooking is also different from a room that remains elevated for many hours. EnvIQ considers temperature, relative humidity, dew point, vapour pressure, persistence and outdoor context together rather than treating one percentage as the answer.
The comparison still has limits. Missing, stale or poorly placed readings reduce confidence, and ventilation advice should consider extraction, safety and the risk of overcooling. Environmental evidence does not diagnose the cause of damp or guarantee that ventilation will dry a room.