Measuring Relative Humidity for Wood Flooring Installers

Posted by Tom Laurenzi on Feb 13, 2016 3:30:00 PM


In our natural environment, there’s always humidity in our air. And this moisture can transfer to anything that’s porous --  from people to food to walls to floors. And the moisture content of the air can vary wildly from desert-like conditions to heavy humidity that can be found in the tropics.

This moisture in the air is possible up to a certain limit — and beyond this limit comes saturation. This is where condensation or fog happens or water droplets will form. The concept of Relative Humidity (RH) dictates what percentage of this maximum amount of humidity is present in the air. For instance, high levels of ambient humidity can be a warning sign at inspection jobs.

Furthermore, RH is also a major concern when installing a wood floor.

The maximum amount of humidity in the air is directly correlated to the temperature of the air. If temperature rises or falls in a closed system, the saturation vapor pressure will increase or decrease. As a result, the RH will drop or rise with temperature changes even with an unchanging amount of water in the air.

When acclimating wood flooring before installation, it’s important to measure both the ambient relative humidity and the moisture content of the wood for a proper, long-lasting installation.

RH Response Times

Response time is often quoted by manufacturers like this: X seconds to get to 90% of the final relative humidity value.

For example, if the RH is actually 80% and the manufacturer claims that the sensor will reach 90% of the final value in 45 seconds, then this means the RH meter will read at least 72% RH (assuming it’s rising) after 45 seconds.

That is still 8% RH away from the final value. It may indeed take 1-5 minutes to get to 80% depending on the many variables that go into relative humidity measurements.  

Response times will vary greatly under certain situations including:

  • Moving air vs. static air environments

  • Age of the sensor

  • Chemicals or vapors present in the environment

A stand-alone thermo-hygrometer such as the Delmhorst’s HT-4000f is used by flooring installers and restoration contractors alike. Some prefer a multi-function meter that includes a moisture meter and a thermo-hygrometer in one device.  The TotalCheck and Navigator Pro 3-in-1 meters are examples of these multi-function meters.


Delmhorst’s HT-4000f

Calibration’s Effect

Calibration can also affect response time. When comparing two meters, although one may appear slower than the other, it’s only because they are ending at different points. Even two meters in calibration may have an endpoint 4-6% apart.

Some wood flooring installers, contractors and wood flooring manufacturers might wonder how long the sensor calibration will last. Due to the fact that there are several causes for RH sensors to drift and/or fall out of calibration, there’s no definitive answer to this question.

How the sensor is stored, as well as the environment in which the sensor is used both impact the life of sensor calibration. While one flooring contractor may find calibration still in tolerance after a year or more, another in a different environment may find drift after only a few months. At one point or another, ALL sensors will lose calibration. All RH sensors must be re-calibrated or replaced periodically.

In-field calibration checks for wood flooring installs can be done by comparison against a second reference sensor or using saturated salt solutions.

For more about in-field calibration, proper operating and storage and other critical factors to consider when comparing RH readings, download our FREE Guide ‘Relative Humidity Sensor Behavior and Care’.

We adhere to nationally recognized standards and practices and use the most accurate equipment available. Each Delmhorst sensor’s calibration is NIST (National Institute of Standards and Technology) traceable and checked against a chilled mirror hygrometer.

For more information about the value of using a RH Sensor along with a Moisture Meter for the best in wood flooring installation contact one of our specialists at 1-877-DELMHORST

Download the eBook, What is the key to Accuracy?

Topics: Wood Flooring Flooring moisture meters restoration professionals