Home Condensation Risk & Humidity Checker
Enter room temperature, relative humidity and a measured surface temperature. The checker compares that surface with the estimated dew point, then helps you decide whether to investigate moisture generation, ventilation, a cold surface or another damp cause.
At this reading, the measured surface is at or below the estimated dew point, so airborne moisture can condense on it under the measured conditions.
Surface minus dew point: -1.2°C
What this pattern suggests checking next
- Check whether the window is wet mainly after sleeping, cooking, showering or indoor laundry; timing helps identify the moisture pattern.
- Check that suitable extraction, trickle vents or other designed ventilation are working and being used as intended.
- Repeat the surface-temperature reading when the glass or reveal is actually wet, especially on colder mornings.
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How to use the reading
Measure room temperature and humidity away from direct steam, strong heat and the dehumidifier outlet. Measure the temperature of the surface you are investigating at roughly the same time. Repeat the check when the symptom normally appears.
Condensation is a surface condition: moisture in indoor air can condense when it meets a sufficiently cold surface. A reading can therefore support or weaken a condensation hypothesis at that place and time, but it cannot identify every source of damp.
Decision aid only: dew point is estimated with the Magnus formula and compared with the surface temperature you entered. This is not a building survey, mould assessment or diagnosis of leaks, penetrating damp or rising damp.
What the result means
- Condensation depends on moisture in the air and the temperature of the surface it reaches; relative humidity alone does not identify a specific condensation point.
- Sensor placement, calibration and timing affect readings, so compare a pattern of measurements rather than treating one reading as a diagnosis.
- A surface above dew point at one moment does not rule out intermittent condensation, leaks, penetrating damp or other causes of persistent damp.
- This tool is a decision aid, not a building survey or diagnosis.
Related guides
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