Analysis of Condensation at the Air Pipe

Article details

This question is very important for the analysis of Condensation at the air duct because if we know the "temperature"

and “relative humidity (RH)” in the ceiling area It will be possible to calculate Dew Point (dew point).

and test whether “the air duct surface is too cold or the insulation is too thin” or not.

🧰 How to check the temperature and humidity in the ceiling.

🧪 1. Use a Combined Thermo-Hygrometer.

(Digital thermometer + humidity)
 • This device has a long probe or sensor head that can be inserted into the ceiling cavity.
 • Can measure both:
 • Temperature (°C)
 • Relative Humidity (%RH)
 • Popular models such as , ,

steps
 1. Open the ceiling at the point you want to inspect.
 2. Insert the probe into the area above the ceiling (be careful of the supply wind blowing directly into it).
 3. Read the value on the machine — e.g.
 • Temp = 28°C
 • RH = 70%
 4. Use both values to calculate Dew Point.

Example of calculating Dew Point:

If temperature 28°C, RH 70% → Dew Point ≈ 22°C
If the duct insulation surface is lower than 22°C → there is a chance that water droplets will form.

🌡️ 2. Use an Infrared Thermometer / Thermal Camera.
 • Can be used to measure the temperature of the air duct surface and the temperature around the ceiling.
 • Some models can immediately display images of “cold spots” that are at risk of condensation.

Usage example:
 • Measure the air duct above the ceiling and find Temp Surface = 16°C.
 • Use a hygrometer to measure the air around the ceiling. Dew Point = 22°C
→ It is concluded that the pipe surface is cooler than Dew Point → The insulation must be improved.


💧 3. Use Data Logger for long-term measurement (for serious analysis work)
 • Install Sensor 2 point:
 • One point to measure temperature and RH in the ceiling area.
 • Another measurement point is the air duct surface temperature.
 • Continuously collect data 24–48 hours.
 • Use the graph plot program to see “at what time the Dew Point is higher than the pipe surface temperature”
→ is the period during which Condense occurs.

Example equipment:
 •
 •
 •


🧮 4. Calculate Dew Point with the formula

Dew Point (°C) ≈ T – (100 – RH)/5

such as
T = 28°C, RH = 70%
→ Dew Point = 28 – (30/5) = 22°C


📋 Summary of inspection guidelines

Tools What can be measured Features When to use
Thermo-Hygrometer, temperature + RH, easy to use, convenient to carry, check at one point.
Infrared Thermometer for pipe surface / insulation, measures cold point quickly. Inspect the pipe at several points.
Thermal Camera: Thermal images, see the Condense point clearly, survey a wide area
Data Logger Temp + RH continuous trend analysis Seriously check for the cause.