The Best Vapor Systems for Basement Walls


When you hear “basement”, do you think of a damp, dreary room under the home where no one wants to go? Fortunately, this doesn’t have to be reality when basements are designed properly. Vapor and moisture barrier systems can keep basements dry and comfortable year round when designed, installed, and maintained properly.

What is a Basement Vapor Barrier?

Vapor barriers or vapor retarders are used to waterproof a basement wall and control where the moisture flows. Vapor barriers are applied to the inside wall frame before the drywall or plaster to keep the materials dry. These materials are literally barriers used to stop the movement of water vapor.

What is a Basement Vapor Barrier?

Water vapor is the humidity that is present in the air. Many materials, including wood, allow some water vapor to pass through. A vapor barrier is used to stop the water vapor from moving in the same way that insulation stops heat from moving. The vapor barrier allows the water to be channeled where it can be drained away and/or controlled being allowed to dry and not lead to problems influencing other building materials like batt insulation and wood framing on the basement walls.

Why Do Basements Need Vapor Barriers?

Basement or foundation walls are subject to three exterior conditions - below grade pressure from the earth, the below grade area (approx. 2' to 4') subject to frost, and the minimal area above grade. All of these areas have a different influence on the temperature change through the wall assembly and how water vapor moves through the basement walls. The dew point creates condensation, as does the interior temperature and humidity, leading to potential problems for mold and mildew on both sides of a vapor barrier.

As the water vapor moves through basement walls, the humidity in the basement will increase and condensation may form. Condensation, or liquid water, can cause building materials to rot, decrease the effectiveness of the wall’s insulation, and lead to mold and mildew problems.

The Best Vapor and Moisture Barrier Systems for Basement Walls

The first step in keeping your basement dry with proper waterproofing and ground water control. Proper downspouts, channeling water away from the foundation, and regular gutter cleaning are all important in keeping the soil around your basement and foundation from becoming saturated.

Even with proper ground water control, you will still need a vapor barrier to keep your basement dry and comfortable. In addition to keeping your basement more comfortable, vapor barriers and waterproofing systems can:

  • Prevent mold and mildew growth

  • Eliminate musty smells

  • Reduce energy bills

  • Lower the entire home’s humidity level

What Are the Best Vapor and Moisture Barrier Systems?

The best vapor barriers or retardants need to be installed in as continuous a manner as possible. Gaps in the barrier can lead to big decreases in the barrier’s ability to block moisture. Any tears or punctures must be sealed, or moisture can collect on the insulation and reduce its effectiveness which could potentially lead to mold or mildew growth.

Some of the most common materials, in traditional construction, used for moisture barriers are: polyethylene plastic sheets, builder’s foil, and foam board insulation. While these materials are fairly easy to install, they can be difficult to install properly. Traditional techniques require whoever is installing these types of vapor barrier to be very detail-oriented during the installation. After construction is complete, it can be very difficult to repair work that was not done properly.

Insulated Concrete Forms for Basement Walls

Insulated concrete forms (ICFs) are and ideal solution for below grade basement and foundation walls, being durable, energy efficient and disaster-resistant. Due to the unique conditions a basement wall is subjected to, ICFs have the natural ability to resolve all these issues and eliminate problems that may occur with traditional construction techniques.

Insulated Concrete Forms for Basement Walls

ICFs come as blocks with a layer of foam insulation on the inside and the outside. A special system keeps the insulation together and allows the blocks to be stacked as needed on site. Once the blocks are placed and rebar is installed, concrete is poured into the blocks, in between the layers of insulation. When the concrete cures, what’s left is an extremely strong structure with inner and outer layers of continuous insulation.

Ground Water Control is Key

Ground water control is important no matter how a basement is protected from moisture, and ICFs are no exception. Keeping water from saturating the soil around the basement is key to allowing the system to work properly. To give the ICF blocks an extra level of waterproofing, ICF walls below grade require a waterproofing membrane - self-adhered or peel-and-stick waterproofing membrane or compatible liquid applied membrane. Additionally, a dimple drainage board layer on top of the waterproofing membrane further improves the basement’s ability to resist moisture.

ICFs Act as Vapor Barriers

ICF walls act as vapor barrier or retardant on their own while also adding an incredible level of insulation. The two levels of insulation coupled with the thermal mass of the concrete not only work as an exceptional vapor barrier for moisture but will also keep the temperature in your basement comfortable and stable. Temperature stability is important for basements because it prevents temperature swings from moisture due to condensation.

The double insulating layers of an ICF moderate the dew point to fall within the concrete layer and never reach the interior face of the wall. The interior wall face does not experience a major temperature swing and will not have condensation for interior humidity or exterior temperatures. These ICFs qualities eliminate health issues related to mold or mildew growth in basements.

Turn to Fox Blocks for ICFs for Basement Walls and More

When deciding on the best moisture barrier/retardant system for basement walls, be sure to take a look at Fox Blocks insulated concrete forms. With a perm rationing of less than 1.0 and impressive strength and insulation, Fox Blocks are hard to beat. When you learn how economical they are and how much time they save during construction, the choice is easy. To learn more about how Fox Blocks can benefit your next project, reach out to their experts today!