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ATMOX Graphic of ATMOX Tom with Crawl Space Fan and ACE Display

Let’s bust this myth: ATMOX fans are just fans on a humidistat.

ATMOX fans are generally connected to a controller. That controller is much more sophisticated than a simple humidistat. Let’s explore what makes a crawl space setup or “ATMOXsphere” different. ATMOX is NOT humidistat fans for the crawl space.

How does a humidistat fan for a crawl space work?

Not all crawl space fans on the market are exactly the same, but most have a similar operation if connected to a humidistat. A humidistat is basically an on and off switch for the fan so that it doesn’t run all the time. Most humidistats have a dial or display to set a targeted humidity level. When the humidity is above the target, the fan will turn on. Conversely, when the humidity is lower than the target, the fan cuts off. This sounds very logical, doesn’t it? Run a fan to lower humidity when it’s high. Not so fast – unfortunately, it’s not so simple.

Temperature Conditions

Let’s think a little bit more about the actual conditions of a crawl space in most geographic areas. In the summer, crawl spaces generally remain at cooler temperatures than the outside air. This can be for a variety of reasons such as being out of direct sunlight or a slight leaking of cold air from air conditioning systems. At the same time, the summer air is hot – sometimes very hot. Depending on your location, the outside summer air can also be very, very humid at times.

Sensor Location

So why does this matter? Most humidistat fans have the sensor for measuring humidity directly on the fan or on a simple humidistat very nearby. So if the fan is installed in a vent location, what air are you measuring? The inside or the outside? The answer is probably a little bit of both. This air near a vent location is likely to correlate to the air directly outside. So now, if the air outside has high humidity, the sensor on that humidistat will tell that fan to turn on. Running when outside humidity is high is when a fan on a humidistat can do the exact opposite of its intended goal.

Unintended Consequences

Remember how the outside temperature is generally warmer than inside the crawl space. That very hot and very humid air from outside is now being drawn into the crawl space with the intent to exchange the air and reduce humidity. However, there is an unfortunate problem. As that air comes into the crawl space, it is being cooled down. If you remember back to middle school weather science, hot air can hold more moisture in it than cold air. So that high humidity air from outside is now colder and can no longer hold its moisture when inside the crawl space. When the air can’t hold the moisture anymore, it will begin to condense on cold surfaces. You have now put actual water into the crawl space! This is obviously not going to help reduce overall moisture in the crawl space. It’s actually possible to make it worse with a humidistat fan depending on weather conditions.

How does ATMOX work in a crawl space?

ATMOX is different. The ATMOX operating principle for running fans with outside air is very simple: Only use outside air when it’s beneficial in reducing moisture and within proper temperature parameters. With the use of the ATMOX controller, all of the fans will operate automatically to meet these conditions. How does it do that?

Sensor Location

The first important difference is that ATMOX uses two sensors. One goes outside to measure the conditions of the outside air. The second goes inside the crawl space to measure what is actually going on in the crawl space. These sensors are recording both temperature and humidity in both locations. Making good decisions starts with having good information. Having accurate data from quality sensors is the first step.

Temperature, Humidity and Dew Point

The second key difference is that ATMOX uses a comparison of the data from the two sensors (inside and outside) to determine which air is actually drier. The fans will only bring in that outside air when it’s actually better and beneficial. An ATMOX controller doesn’t just look at humidity. ATMOX actually calculates dew point to get a more accurate measure of moisture in the air.

Without getting too technical, it is important to remember that humidity is actually called relative humidity, because it is relative to a specific temperature. Therefore, as temperatures change and fluctuate, humidity can bounce around and be a very misleading measurement of moisture in the air. Humidity of 90% at 95 degrees is a lot, lot wetter air than humidity of 90% at 50 degrees. Remember there are sometimes big differences in temperature between daytime summertime outside air and crawl space air. ATMOX controller will also make sure outside air isn’t too cold or too hot before running fans – a humidistat won’t take that into account.

Dry outside air from crawl space fans is an incredible tool to reduce moisture. The key is to make sure that it is being used at the right time – an ATMOX controller does just that.

Post Author: ATMOX TOM