Dehumidifiers in crawl spaces

There are several different types of dehumidifiers, varying in size, capacity, and technology. Which one is suitable for your home depends on a few different factors.

The three most common dehumidifier technologies include:

Thermal dehumidification works by slowly heating the air in your crawl space. This causes the heated air to carry moisture out through the ventilation. The fact that it heats the air slowly means that the warm air does not release moisture until it is swept out through the ventilation.

This type of dehumidifier utilizes natural forces in a smart way and only operates when needed. This makes them a truly energy-efficient option.

The downside is a relatively high initial cost and that it requires professional installation. An incorrectly installed thermal dehumidifier can cause both moisture damage and fires.

The advantage is the low operating cost and the relatively low operating cost.

If you have a crawl space that is properly sealed, a sorption dehumidifier can be a good solution. This type of dehumidifier is even called a crawl space dehumidifier, and the technology has been around since the 1940s. A great advantage of this type of dehumidifier is that they are effective even at very low temperatures.

The sorption dehumidifier uses a powerful fan to draw humid air into a rotor. The rotor in the machine is treated with moisture absorbents that attract moisture. When the rotor's capacity is full, hot air flows through the rotor and the water evaporates. The steam is then led out of the crawl space via a steam gas hose.

The advantages are that it is a familiar and well-proven system that also works at low temperatures.

The disadvantages are that many older models can be energy-intensive, so buy a new and modern model. You will get the best results if the crawl space is properly sealed.

A condenser dehumidifier is not always suitable for a crawl space as it works best in environments with a temperature above +15°C to truly work efficiently and economically. However, this may be changing. More and more modern condensation dehumidifiers are now capable of working at temperatures as low as +2-3°C.

The technology works by the dehumidifier drawing in warm and humid air and cooling it down so that the water separates from the air. The water is then collected in a tank or led directly into the floor drain.

Condenser dehumidifiers/compressor dehumidifiers/refrigerant dehumidifiers are best suited for indoor environments. They are ideal machines for, for example, laundry rooms or insulated basement spaces, but not for crawl spaces.

If you're unsure whether you truly need a dehumidifier in your crawl space, you can start by measuring the humidity level in your crawl space. To get a good overview of the crawl space's condition, it can be helpful to measure the different materials in the crawl space with a moisture meter (pin-type meter).

Measure and record the moisture levels of the different materials and research what is acceptable for each material. This method will give you a better basis for making a decision than if you only use a hygrometer – which merely gives you a daily value of the crawl space's condition at the time of measurement.

A homeowner should perform regular checks of their crawl space to ensure everything is in order. A moisture problem detected early is significantly easier to resolve than a problem that has had time to spread.

If the moisture meter shows more than 16% moisture in the material, you have a moisture problem that likely needs to be addressed. If hygrometer readings show that humidity exceeds 75%, the humidity is high enough that you risk mold growth.

When inspecting the crawl space, you should also visually examine the foundation. Look out for discolorations and coatings that could be mold or rot damage. Pay extra attention to the north side of the house, as it is the coldest side. It is often on the northern parts that moisture problems first tend to appear.

If the readings indicate that you have high moisture levels in the crawl space, it's time to do something about it. Postponing the problem will most likely lead to bigger problems later on. Moisture damage has the ability to grow exceptionally fast once it reaches a certain level.

Rot damage and mold are both costly and troublesome to get rid of once they have taken hold. In the worst case, you may need to replace entire parts of the house's structure to completely eliminate the problems.

A clear advantage of having a dehumidifier in the crawl space is that it also handles radon and keeps mold spores at bay. In other words, you may be interested in a dehumidifier even if the humidity levels look good.

A good dehumidifier can act as insurance against future problems and at the same time be beneficial by keeping various toxic gases at bay, which would otherwise rise into your house.