Brennan Homes Blog

Posted on March 9, 2022

Correcting condensation on basement foundation walls

Categories: Educational

In a previous article we talked about condensation on the interior of a basement foundation wall. We talked about the condensation being a result of two primary things—the moisture in the interior air and the temperature of the interior side of the exterior wall. The first thing to check once you have determined that the problem is condensation is to make sure that the relative humidity is not too high. In our heating climate we typically have relative humidity levels between 30% and 40% during the winter months. As the temperature goes down outside so should the relative humidity in the house. If the humidity is too high make sure that there are no sources causing the humidity such as a clothes dryer not vented to the outside or cooking without venting to the outside. Both of these can product contribute to excessive humidity.


If the humidity is within a normal range then you may want to consider insulating the basement walls.

The goal of insulating the walls is to reduce the amount of warm moist interior air that comes in contact with the cold foundation wall. A good method to accomplish this is to use a rigid foam insulation that is secured directly to the foundation wall with an adhesive specifically designed for this application. Apply the adhesive continuously to the top and bottom of the wall and then intermittently in between to secure the panels. The panels are typically available in 4’x8’ and 4’x9’ sheets. Minimize any gaps between sheets. If necessary the panels can be attached with nails or mechanical fasteners to help hold them in place until the adhesive cures. Once the adhesive cures the joints between the panels should be taped with a tape designed to work with the product.


This is actually a good do-it-yourself project and can be completed with a minimum of tools. If installed correctly almost no air will penetrate the insulation or get behind the insulation to the concrete foundation wall. And the nice part is that even if some air get behind the insulation, the rigid insulation is unaffected by moisture and should not result in damage.


If you choose to insulate your basement you will also reap other benefits. Obviously it will help reduce or eliminate dampness or frost on the exteriors walls. You will benefit by lower heating bills due to improved insulation and possibly reduced air infiltration/exfiltration. You may even be able to raise the interior relative humidity thereby improving the comfort in the home. And finally you can take satisfaction in completing a good do-it-yourself project.

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