Lower levels of your home, like basements and crawl spaces, are dark and damp in nature and are prone to moisture problems. Unfortunately, moisture problems in the lower levels of your home can also create issues inside your home. One major culprit for humidity in your home is a phenomenon called the “stack effect”.

The stack effect refers to the process in which hot air leaves the home through your attic and upper levels. As it does, a vacuum is created below, and new air is pulled upwards through the basement, crawl space, and lower levels.

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Relative Humidity & Your Home 

We know that air enters the home through the lower levels, moves upwards through the home, and exits through the upper levels. What happens if outside air is being pulled into the basement or crawl space through vents or other openings?

Basements and crawl spaces are naturally cooled by the earth around them which keeps a fairly constant temperature year-round. Any air that enters that space from outside will be cooled as well.

Imagine this: It’s an 80 °F (27 °C) day with 80% relative humidity. The higher the relative humidity number is, the closer the air is to becoming “full” of water. Warm air holds the most water and as it cools and “shrinks”, it’s able to hold less water. The relative humidity number shows how much humidity is in the air, relative to how much it can hold. Air at 80% relative humidity is 80% “full” of water. When the humidity rises above 100% outside, it rains.

Picture that humid air moving into your crawl space or basement. This cool, underground space drops the temperature of the air to 68 °F (20 °C). Because of this, the air’s relative humidity goes up, even if no new water is added to the air. For every 1 °F the temperature drops, the relative humidity of the air will rise by 2.2%.

In this case, the relative humidity will rise by 26.4% (12 °F x 2.2%). Add the 80% humidity you already had, and you have 106.4% relative humidity. However, when the humidity reaches 100%, the air can hold no more water! So this extra humidity is dropped from the air as condensation, which is deposited on cool surfaces in the space, such as wood, metal or concrete.

Mold Spores and Your Home 

Mold needs moisture to survive, and it draws this humidity from the air around it. As the relative humidity in your basement or crawl space rises to 60% or higher, mold will live, thrive, and survive in the space.

According to the Journal of Property Management, mold can reproduce as much as 10 million spores in just one square inch of drywall. If you take that across all the walls in your home, this can be an overwhelming issue and lead to allergy issues in your home.

Now think about the air you breathe in your home. Time Magazine reports that there can be hundreds of thousands of mold spores in a single cubic meter of air, and a person inhales 10-12 cubic meters of air each day.

Because of the stack effect, these mold spores will not be confined to your basement or crawl space. As air moves up from these spaces into your home, it will bring mold spores and humidity along with it. If you notice that you suffer from symptoms such as a runny nose, watery eyes, mild allergic reactions, a scratchy throat, fatigue, or headaches at home that seem to disappear once you leave the building, mold allergens may be the culprit.

Controlling Humidity and Mold

Mold depends on moisture to thrive. In order to get rid of the mold in your basement or crawl space, you must attack the initial moisture problem at hand.

At Foundation Recovery Systems, we recommend starting by sealing off any vents, covering any exposed dirt and concrete, and installing airtight crawl space doors. Replacing drafty basement windows will also help hold back outside air.

After those have been taken care of, we recommend installing a dehumidifier in your basement or crawl space to remove any other humidity in the air and keep it permanently dry.

Dedicated to your home. Dedicated to you. 

At Foundation Recovery Systems, not only do we fix the issue, but we’ll also provide constant communication throughout the entire process and educate you on exactly what’s happening so that you know how to prevent other issues in the future.

We offer free basement & crawl space humidity control inspections in central Missouri and Eastern Kansas, including Kansas City, Columbia, Moberly, and Springfield. Contact us today to get started!

Even when your home is protected from outside humidity, your home can still experience humidity when sources of standing water exist in your home. Install a sump pump system to prevent groundwater flooding, and be sure to actively look for plumbing leaks— especially in your crawl space.