What Causes Frost on the Inside of Basement Walls?

High levels of moisture are often found in basements, and they can lead to a variety of problems such as mold growth or damage to your home's structure. Although the heat and humidity of the summer months often cause indoor moisture levels to rise, cold weather can also cause moisture problems such as condensation or frost on windows and walls. When frost is present on interior basement walls, it is indicative of too much moisture in the air inside your home.


Dampness and high humidity are common basement problems. This is usually caused by moisture moving up through the foundation of your home. Once moisture begins to evaporate, it causes excess moisture in the air and a rise in humidity. Condensation occurs when warm air meets colder air next to windows or walls. The cooler air causes moisture to adhere to surfaces in the form of condensation. If frost forms, your basement may lack the proper amount of insulation. The development of frost on any surface inside your home is an indication that you have a moisture problem.

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When frost develops on your interior basement walls, it can lead to water stains and eventually damage the wall. The excess moisture from condensation and frost may lead to mold growth. Mold fungi are found both indoors and outdoors, germinating on wet moist surfaces. Mold growth in your basement may damage your walls and cause adverse health effects for those living inside your home.


Adding insulation to your basement walls may help warm the surface of the wall, reducing condensation and frost. Fiberglass insulation in the form of batt and rolls is commonly used to insulate basement walls. Foam board insulation is another type of insulation used in basements. Sprayed foam insulation and loose-fill insulation are also good choices for finished basements. Inspect your basement for any gaps that can allow air to seep inside your home. Seal all gaps with caulk, and cover larger gaps with foam board insulation to close.


When condensation and frost are a problem inside your basement, the indoor humidity level may be too high. Indoor humidity should range between 30 and 50 percent to prevent mold growth and condensation. Inspect the ground outside your home. It should be sloped away from your home to keep rain and surface water from running inside your basement. If the ground is sloped toward your home, regrade it. Keep your downspouts free from debris to keep them from overflowing into your home. The less moisture inside your basement, the fewer problems you will have with condensation, frost, mold and high humidity.