Basement Concrete Wall Insulation

When building a new home it is important to take every step to make sure it is as energy efficient as possible. A significant amount, as much as 33%, of the home’s energy is lost through an unfinished basement and it would be hard to consider such a home as being energy efficient. An insulated and finished basement greatly increases the functional space and value of the home, and there are many reasons why basement walls insulation is so important. There are three basic ways of insulating the basement of a home: 1. Exterior. 2. Interior. 3. Middle.

Exterior insulation is not common due to the high cost and difficulty of protecting the insulation from damage. Because of its low cost the most common method of basement insulation is the interior method, which will be discussed in this article.

The most traditional method of insulating a basement is through the use of fiberglass batts. In this method, the walls are constructed and the voids between the studs are filled with fiberglass insulation, covered with a vapor barrier, and finally finished with drywall. This method of insulation has one very serious problem: Moisture. As the concrete cures it releases a great deal of moisture. The fiberglass insulation soaks up this moisture, which is trapped by the vapor barrier. As the fiberglass begins to saturate it quickly looses its effectiveness. Mold will begin to grow in the fiberglass as well as on the surrounding surfaces, causing the studs and even floor joists to rot. Also, any moisture that enters the foundation from the outside will contribute to the problem. This is why the basement wall insulation you choose must also be an approved concrete vapor barrier.

A better option is to install a layer of extruded polystyrene (XPS) directly to the concrete wall. 2” of XPS would meet the R-10 requirement of Climate Zone 4. The next step is to build the perimeter walls directly interior of the XPS layer. This provides a convenient place to route electrical wiring and plumbing, as well as facilitate the hanging of drywall. While not necessary, it is common to fill the voids between studs with fiberglass insulation, but again, the drawback to this method is that excessive humidity in the summer months may be a problem due to the intolerance to moisture that fiberglass possesses by nature. If the humidity is not controlled mold, fungi, and odors may develop.

A solution to these problems mentioned above would be to use Ecofoil’s bubble foil insulation. EcoFoil bubble insulation products are approved Class 1 Vapor Barriers with a perm rating of < 0.02, making them resistant to the effects of moisture. EcoFoil’s reflective bubble insulation is safe and easy to install with a utility knife and staple gun, unlike fiberglass which contains harmful fibers and is difficult to handle. If foil bubble insulation is used with rigid foam board, the gap created between the XPS and the drywall creates the airspace you need which allows for the reflection of up to 97% of radiant heat. However, EcoFoil’s double foil bubble insulation has an R value of 8.5, which may be sufficient to use as standalone insulation by itself in warmer climate zones. In this case, you would need to create recesses within the stud cavities during installation as shown in this document (PDF): How to install reflective insulation in basement walls.

In conclusion, it is important to look at all levels of a home when trying to maximize its energy efficiency. The days of cold, dark, and damp basements are in the past; today’s homes utilize every square inch of space, including the basement. Protect your investment and your family by choosing a method of insulation that is long-lasting, safe, and environmentally sound. The best insulation for basement walls can be found at

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