The Nest sensor is a reliable and accurate smart thermostat that will automate and optimize your in-home temperatures.
It also comes with a hygrometer that’ll measure the surrounding water vapor and help you regulate indoor humidity.
As such, if it’s reading the wrong humidity levels, it can tell the connected humidifier/dehumidifier to make your home too damp or dry.
The Nest humidity sensor can get wrong readings if it’s exposed to air currents, direct sunlight, or fluctuations in the humidity of the mounted wall. To fix this, reduce the sensor’s exposure to airflow, sunlight, and control the moisture levels of the mounted wall.
In this article, I’ll share with you the various reasons why your Nest sensor might be showing wrong humidity readings.
After that, I’ll share four easy fixes to resolve the problem and get the correct humidity readings.
Why a Nest Humidity Sensor Is Showing Wrong Readings
The Nest humidity sensor is very accurate when measuring humidity levels in its immediate surrounding.
It’s only off by a few percentage points from lab-grade humidistats and hygrometers.
As such, if you’re getting an incorrect humidity reading, it’s most likely picking up the fluctuating humidity levels surrounding the device.
Here’s a look at some of the most common reasons why you’re getting the wrong humidity readings from the Nest sensor.
Exposure to Outside Air Currents or Drafts
If you place the Nest sensor in an area with too much airflow, that can affect the humidity readings.
For example, outside air currents coming from a nearby window will have a different level of water vapor saturation compared to what’s indoors.
If it comes in direct contact with the Nest sensor, it will throw off the humidity reading.
The same applies if the Nest sensor is placed in an area of your house that catches a draft.
Circulating Air Inside the Wall Cavity
Did you know that there might be air circulating inside your wall cavities?
If you have a large house, exposure to sunlight or the use of a heater/cooler in one room will cause a temperature difference.
The varying temperature can create a convection current where hotter air within the walls moves to colder areas, resulting in airflow inside the wall cavity.
If there’s high air circulation behind the wall where the Nest sensor is mounted, that’ll affect its humidity readings.
Wall Humidity Level
The condition of the wall on which the Nest sensor is mounted will significantly impact its readings.
If you mount the sensor on a wall with piping, it can show very high humidity readings.
This is more so the case if the pipes within the walls are leaking.
The same holds for walls that are damped for whatever reason.
The Nest sensor will pick up on the extra moisture and inflate the humidity readings drastically.
Exposure to Direct Sunlight
If the Nest sensor is in contact with direct sunlight, that’ll tamper with the humidity readings.
The sun will heat the wall as well as the sensor itself.
At first, this will affect the overall temperature readings.
Then, the heated surface will mess with the surrounding moisture levels, which will throw off the humidity readings.
How To Fix Nest Humidity Sensor To Get Right Readings
Most of the factors for a wrong reading on the Nest humidity sensor result from its immediate surroundings.
Exposure to in-house draft, outside air currents, direct sunlight, and the condition of the mounted wall are all factors that can affect the humidity readings.
The best way to fix this problem is to mount the sensor on a clean and solid (non-hollow) wall that’s away from sunlight or any airflow.
That said, conventionally, installing the Nest sensor requires you to drill a hole in the wall and pass through a lot of wiring.
So it’s not that easy or even feasible for some people to shift and mount the sensor in a different location.
With this in mind, I’ve curated a list of 4 easy fixes to get your Nest humidity sensor showing the correct reading.
1. Reduce Air Current Inside the Wall Cavity
Air currents inside the wall cavity result from temperature differences in different parts of your house.
As such, if you regulate the temperature throughout your home — so it’s the same everywhere — that can solve this problem.
However, doing this can be difficult if you live in a large multi-story house.
In that case, the only solution you have is to mount the Nest sensor on a solid, non-hollow wall.
2. Control Wall Humidity Levels
If you mounted the Nest sensor on a wall with water piping running inside it, that could influence the humidity readings.
You cannot completely remove this factor, but you can reduce it.
Installing better pipes and ensuring no leakage will keep the moisture level inside the walls at a minimum, reducing its effect on the Nest sensor.
3. Avoid Direct Sunlight
If the sunlight is coming from a nearby window, keeping it shut or pulling the curtains is one of the easiest ways to remove sunlight exposure from the Nest sensor.
However, if you need some sunlight coming in, I’d recommend installing a cardboard piece beside the sensor to shield it from direct sunlight.
Now, do note, this isn’t a 100% resolution.
The sunlight can be hot enough to warm the walls in the summer, influencing the humidity readings.
4. Call Tech Support
If all the discussed methods fail, then it’s time to call tech support.
It’s always possible that there’s some software bug or a calibration issue that’s causing the wrong reading on your Nest sensor.
Alternatively, the problem can also stem from a fault in the in-built hygrometer.
The Nest support team can quickly help you out with these problems.
Key Takeaways
In conclusion, your Nest humidity sensor can show wrong readings if it’s exposed to outside air currents, drafts, as well as direct sunlight.
The condition of the mounted wall, including its humidity level and any air currents within the wall cavity, can also influence the humidity readings.
As such, the simplest way to get accurate readings from your Nest humidity sensor is to move it to an area that’s not affected by these surrounding factors.
But if that’s not possible, you can try to remove or limit exposure to air currents, sunlight and control the wall temperature and humidity levels.