Module 4 · Tools & Equipment
4.2 Hygrometers & Thermo-Hygrometers
7 min read
If a moisture meter tells you a wall is wet, a thermo-hygrometer tells you why. It is the cheapest genuinely diagnostic instrument in the kit and the most neglected by beginners, who tend to buy a better meter instead. This lesson covers what to measure, where, and how to avoid the handful of errors that make the readings worthless.
Learning objectives
By the end of this lesson you will be able to:
- Use a thermo-hygrometer to record air temperature and relative humidity correctly.
- Measure surface temperature and compare it against dew point.
- Identify the placement errors that invalidate humidity readings.
- Explain why a single snapshot reading has limits, and what to do about it.
Key terms
- Thermo-hygrometer
- An instrument reading air temperature and relative humidity, usually calculating dew point too.
- Infrared thermometer
- A spot device reading surface temperature from a distance. Affected by surface emissivity and by reflections.
- Data logger
- A device recording temperature and humidity over days or weeks, capturing the overnight peaks a visit misses.
- Acclimatisation
- Letting an instrument reach the conditions of the space before trusting it — typically several minutes.
Free — enrol to continue
Read the rest of Tools & Equipment
Module 1 is open to everyone. The remaining six modules — building science, each damp mechanism in depth, meters and thermal imaging, the full inspection method, and report writing — are free too. We just ask for an email so you can pick up where you left off, and so we can send your certificate when you finish.