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DEW-POINT SCREENING TOOL
Condensation Risk Calculator
Check whether a surface is at, below or close to ambient-air dew point using the toolbox psychrometric saturation basis.
Compare a surface temperature with the dew point of nearby air.
Explain this screen
Use this when: Screening a cold surface using known air temperature, humidity and surface temperature.
This helps you: See the surface-to-dew-point margin and your explicitly selected caution margin.
How to use it
- Choose °C or °F, then enter nearby air temperature and humidity.
- Enter surface temperature and an explicitly selected caution margin.
- Review the screening status and confirm the actual site conditions.
Before relying on it: The caution margin is a user input, not a universal requirement. This screen does not model thermal bridges or transient moisture effects.
Show example inputs
Learning example only. These values are not measured data or recommended Project criteria.
- Air temperature
- 25 °C
- Relative humidity
- 50%
- Surface temperature
- 15 °C
- Caution margin
- 0 K
Temperature of the air relevant to the surface check.
Help with ambient air dry-bulb
Where to find it: Pair nearby air temperature and humidity from the same condition.
If you don’t know: Obtain the air condition before screening the surface.
Relative humidity of the air relevant to the surface check, entered as a percentage.
Help with ambient rh
Where to find it: Use the humidity reading paired with nearby air temperature.
Example: Enter 50 for 50%, not 0.50.
If you don’t know: Obtain the paired reading instead of assuming measured humidity.
Temperature of the actual surface being checked.
Help with surface temperature
Where to find it: Use an appropriate surface measurement or clearly identified estimate.
If you don’t know: Measure or establish the surface condition; air temperature is not a substitute.
An explicitly selected temperature-difference margin above dew point.
Help with optional caution margin
Where to find it: Use your stated screening criterion; this is not a built-in requirement.
If you don’t know: A zero margin checks the dew-point boundary only and does not define a safety requirement.
Dew point: 13.864 °CSurface − dew point: 1.1361 K / Δ°CSelected caution margin: 0 K / Δ°C
What this result means
The status compares the entered surface temperature with calculated air dew point and the selected caution margin.
Check: The caution margin is a user input, not a universal requirement. This screen does not model thermal bridges or transient moisture effects.
Why this result?
The existing engine flags surfaces at or below dew point and distinguishes a separately selected caution margin.
Calculated from the current entered values; these values are not independently verified measurements.
- Ambient dry-bulb
- 25 °C
- Ambient relative humidity
- 50 %
- Surface temperature
- 15 °C
- Caution margin
- 0 K
No universal safety margin is assumed. The optional caution margin defaults to zero; enter a project-specific allowance if required.
Engineering Method & Assumptions
The calculator derives ambient-air dew point from dry-bulb temperature and RH using the toolbox saturation-pressure basis, then compares measured/estimated surface temperature with that dew point. A surface at or below dew point is flagged as condensation-likely. This is a screening tool; it does not model thermal bridges, radiant exchange, transient moisture storage, air leakage, insulation ageing, surface films, or local humidity stratification.
Scope
This is a steady-state screening check. Use measured or defensible surface temperatures and project-specific margins; detailed envelope/insulation analysis remains a separate engineering task.