Hygrometers & Temperature: Effects & Best Practices

hygrometer with hands


"It's not so much the heat as it is the humidity."

While this is one of the ultimate "dad jokes" of winter, there is some truth to it in the world of flood damage restoration.

When it comes to quantifying and qualifying excessive moisture in a space, the readings from traditional professional moisture meters are only part of the equation. Certainly, moisture meter measurements are vital for determining the level of moisture content present. However, moisture meter readings do not provide two other important pieces of data – temperature and humidity.

Both metrics, which are measured by a hygrometer, make for a more complete understanding of initial moisture intrusion as well as the success of moisture remediation efforts.

Anyone who has ever dealt with a flood damage restoration situation knows humidity can be one of the most damaging factors when it comes to maintaining property integrity. And high humidity goes hand-in-hand with warmer temperatures.

Hygrometers provide another view of moisture presence in a space – one that should not be overlooked.

Why a Hygrometer Makes Sense for Flood Damage Restoration Surveys

To get right to it, there's really no reason not to use a hygrometer when conducting a moisture inspection after a flood damage event.

Unlike a pinless or pin-type moisture meter – which measure moisture presence and content, respectively – a hygrometer measures a space's ambient conditions. More specifically, a hygrometer measures relative humidity (Rh), a reading the comprises temperature, dew point, and grains per pound (GPP).

Inside a building that's experienced flood damage, hygrometer readings are invaluable at all stages of the restoration process. 

    • During the initial part of a survey, they help zero-in on areas of concern. 
    • With moisture remediation and repair, hygrometer readings show the effectiveness of drying efforts. Hygrometers can be used to measure the output of the dehumidifier to make sure the RH levels are coming down.
    • Along with moisture meter readings, hygrometer measurements provide proof that a space’s ambient conditions are brought back to a pre-loss state. 

An essential tool in a surveyor’s kit, hygrometers provide another means to determine the extent to which unwanted or excessive moisture has entered a space.

Temperature’s Effects on Hygrometer Readings

The relationship between temperature and hygrometer readings is straightforward.

In simplest terms, temperature directly impacts hygrometer readings. 


Temperature affects the ambient environment and the amount of humidity (what a hygrometer measures) in the air.

Just like outdoors, when air is warm inside a space it holds more water vapor. The warmer the temperature, the more water vapor is present. Conversely, colder temperatures prevent air from holding water vapor. 

Because the temperature inside a space isn't uniform (think a basement being colder than a second-floor bedroom), it can pose issues in taking readings. What's more, sudden shifts in temperature – if someone opens a door or window to the outside – immediately impact humidity.

In addition, if a hygrometer isn't properly calibrated or attuned to the environment, its sensitivity – and thereby, accuracy – is skewed, meaning temperature fluctuations are more impactful.

Taking Accurate Hygrometer Readings

The #1 thing with taking hygrometer readings as part of a flood damage restoration survey: they take time

To that end, it can take anywhere between 10 minutes to several hours to take a reading during a flood damage restoration survey. Using the best hygrometers, however, it should only take a few minutes to acclimate and take accurate and comprehensive readings. As the temperature of a space can impact the level of humidity, it’s important that the hygrometer is given sufficient time to take a reading. 

The next most important thing: taking accurate readings requires context. That's why to effectively gauge Rh in a space, you'll need to take four measurements with your digital hygrometer:

  1. Outside – to understand the natural state of humidity
  2. The unaffected area – spaces inside a structure that are not impacted by a flood damage event
  3. The affected area  – the room(s) impacted by flood damage that are being dried out (this is the second-hottest space in a building)
  4. The output of dehumidifiers in the affected area – the air being circulated as moisture is removed

To efficiently collect these measurements, take them in temperature order, working from the coldest temperature up to the warmest. While you can take measurements out of order, be aware this will take longer as the hygrometer will need more time to adjust to differences in temperature.

With these four measurements, you'll have a better picture of an environment's moisture level – both inside the affected space and the areas around it, which can be included in a final damage and recovery report. You'll also have key information about the progress of moisture remediation efforts.


Pro Tip: It’s not just ambient temperatures that affect a hygrometer’s readings. The temperature of a hygrometer itself can be problematic. If the device is left in a car on a hot summer day or in the middle of winter, it will need time to get to room temperature. Any readings taken before then are at a high risk of being inaccurate. 

Beyond Rh | Surface Temperature Readings

Next to measuring Rh, the most important readings a professional hygrometer can take are surface temperature readings. These additional readings are taken with a thermo-hygrometer – a close relative of a hygrometer. 

What is a thermo-hygrometer? Essentially, it’s a hygrometer that has a surface temperature thermometer built in.

In flood damage situations, temperature measurements are critical to preventing secondary damage. In simplest terms, if a space hasn't been properly dehumidified and dried out, moisture in the air is likely to condense on surfaces that are cold (this is no different than your mirror fogging up when you take a hot shower). Condensation can cause a host of issues, including:

  • Mold growth
  • Drywall/plaster deterioration
  • Wood rot
  • Musty odors

With a hygrometer that takes surface temperature readings coupled with Rh readings, you're able to calculate proximity to dewpoint – or the likelihood condensation will form – for tested surfaces. This allows you to take targeted action and prevent the potential damage caused by moisture a second time around.

Buying the Right Hygrometer

As with any moisture reading, a measurement is only as good as the device taking it.

When evaluating your next hygrometer or thermo-hygrometer, make sure it has:

  • Accuracy of +/- 2% or better
  • Open ventilation for fast-response reading
  • Replaceable probes
  • A protective carrying case
  • Probe extension cables

With these features in place, you'll be able to take accurate, reliable hygrometer readings that help you better understand moisture's full presence in a building after a flooding event and prevent secondary damage to your property.

Hygrometers for Complete Flood Damage Restoration Inspections

When it comes to flood damage restoration, having a complete understanding of the moisture levels in a space is crucial. This includes taking into account not just the traditional readings from professional moisture meters, but also temperature and humidity.

By doing so, you can better assess the initial moisture intrusion as well as remediation efforts. In addition, high humidity and warmer temperatures often go hand-in-hand. Put simply, hygrometers provide an important view of moisture presence that should always be captured and considered.

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