Should you open the windows?
Add your indoor reading and local outdoor conditions to compare how much moisture is in the air.
Inside your home
from hygrometerOutside conditions
How the decision is made
Relative humidity alone can mislead: cooler outside air may show a higher percentage while carrying less water. WindowWise compares absolute humidity (g/m³), then estimates the relative humidity of that outside air after it warms to your indoor temperature.
Decision thresholds
Open: outdoor air contains at least 1.0 g/m³ less moisture than indoor air. Briefly ventilate: 0.4–0.9 g/m³ drier. Keep closed: outdoor air is as damp or damper. Rain warnings reduce the recommendation to brief ventilation.
Important limitations
Outdoor values are local weather-model estimates, not a sensor at your window. This tool supports ventilation decisions; it does not diagnose damp, leaks or mould. Persistent condensation or mould needs investigation.