Measuring Moisture: Answers to 3 Top Thermo-Hygrometer FAQs

Posted by Tom Laurenzi on Dec 31, 2015 10:57:00 AM

Thermo-hygrometers are useful for checking moisture in the air over a large area.Here on the Delmhorst blog, we frequently talk about the benefits of moisture meters, those devices that can take a moisture content reading in different building materials.

While immensely useful for testing building materials, you often need a reading of the environmental conditions as well. For this task, you need a thermo-hygrometer.

Although many are familiar with moisture meters for home inspectors, contractors, and the like, many people don’t know as much about thermo-hygrometers.  

To help you gain a better understanding of the usefulness of a thermo-hygrometer, here are a few answers to some frequently-asked thermo-hygrometer questions:

1: What Makes Thermo-Hygrometers Different from Moisture Meters?

Thermo-hygrometers are very different from both pin and pinless moisture meters.  

Whereas pin and pinless moisture meters are designed to take a %MC reading of the moisture in a specific building material, thermo-hygrometers measure the temperature and relative humidity (RH) in the air for a given area.

2: What Are Some of the Common Issues with Thermo-Hygrometers?

There are a few challenges to overcome when using thermo-hygrometers, just like there would be with any other piece of testing equipment. Common issues include:

  • Accounting for Temperature. When taking an RH reading for a given area in a structure, the ambient temperature can affect the accuracy of the reading. The higher the humidity, the more the temperature will affect the reading. For example, if the RH in a room is 80% at 33 °C, (91.4 °C), the a change of 1 °C (1.8 °F) would alter the RH reading by as much as four percent.

  • Sensor Tolerance. Every thermo-hygrometer has a built-in margin of error, or “sensor tolerance.” This means that, for any given reading, there may be a difference between the reading given and the actual RH of the area. For example, if the sensor tolerance value of a hygrometer is 3%, and the RH of a room is 33%, then the device may return a sensor reading between 30% and 36%.

  • Care and Maintenance. RH sensor materials will degrade over time as they are exposed to contaminants in the air. This will eventually cause the thermo-hygrometer to lose accuracy over time. This sensor drift can compromise reading results, which means the sensor material will eventually have to be replaced.

Despite these issues, thermo-hygrometers are still invaluable tools for building inspectors, flooring contractors, and restoration specialists.

3: Why Would I Need a Thermo-Hygrometer?

Considering that thermo-hygrometers don’t allow for a specific reading of %MC like moisture meter readings would, why would you need one of these devices?

Common uses for thermo-hygrometers include:

  • Moisture Intrusion Detection. Since thermo-hygrometers get a reading of the relative humidity in the air over a large area, such as in a room of a building, they are useful for detecting signs of moisture intrusion. If a room has an abnormally high RH, there is a good chance there are building materials in the room that have been moisture-compromised. This allows you to narrow your search for a moisture intrusion source to the room(s) with a high RH.

  • Checking RH for Acclimating Wood. When acclimating flooring or structural lumber for use in a building, it’s important to make sure that the wood is properly acclimated. Since wood is a hygroscopic material, it will absorb or bleed moisture until it reaches equilibrium with the surrounding air. Knowing the RH of the air in a structure gives you a better idea of how close a sample of wood is to reaching equilibrium moisture content (EMC).

  • Checking Concrete Slabs. Contractors working with concrete use thermo-hygrometers with in-situ probes to check the moisture conditions deep in the slab. This is critical to following the ASTM F-2170-11 standard, and lets contractors know when a slab is ready to be built on.

Properly cared for and maintained, thermo-hygrometers are incredibly useful tools for any specialist who has to account for ambient moisture conditions on the job.

Topics: Moisture Content Equilibrium Moisture Content thermo-hygrometer ASTM Thermo-Hygrometers