Insulating Your Basement Walls: A Guide

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Home Improvement

There are three main methods for insulating a basement: exterior insulation, insulation within the foundation, and interior insulation.
iStockphoto/George Peters

Many homes today have basements, but in the past, cellars were more common. These were often damp and cool, providing the perfect environment for preserving perishables. However, with modern building techniques, basements are now an integral part of many homes, housing important utilities and functioning as a flexible space for various activities. Unfortunately, basements can be damp and cool, leading to heat loss and water seepage. Insulation can help keep your basement comfortable and dry.

There are three main ways to insulate a basement: exterior insulation, insulation within the foundation, and interior insulation. Exterior and middle insulation are typically done during the construction of the house, but interior insulation is the most practical method for existing homes. It’s also the most cost-effective, but it can lead to moisture problems if not done correctly.

Before you start insulating your basement, it’s important to understand the basics and any building requirements in your area. You’ll also need to determine the R-Value (thermal resistance) of the insulation you’ll be using. This information can be found in the International Energy Conservation Code, which provides recommendations for different regions in the US.

Tools You’ll Need for Insulating Your Basement Walls

Local building codes may require that your insulation be covered with drywall or another finished material. Check with your local building department to ensure that your project meets code. To insulate your basement walls, you’ll need to purchase insulation materials and the following tools:

  • Safety goggles
  • Gloves
  • Utility knife
  • Straight edge
  • Tape measure
  • Stapler
  • Staples
  • Caulk gun
  • Caulk or spray foam insulation

The tools needed for installing insulation include safety glasses, dust mask or respirator, protective clothing, stapler (electric, standard, hammer type), three-eighths or half-inch staples, work light, extension cord, tape measure, utility knife and blades, straightedge for cutting insulation, and stepladder. Other useful items may include expanding foam sealant, caulk and caulking gun, chalk line, gypsum drywall, 2 x 2 lumber, tape, extruded polystyrene foam, power-activated gun with fasteners, construction adhesive, wire insulation hangers, noise protection for ears, masonry screws, drill and carbide drill bit, and asphalt roofing cement.

In some cases, it may be best to call a professional for insulation installation, and the Insulation Contractors Association of America (ICAA) can provide a list of local contractors. Homeowners have access to different materials for insulating basement walls, including blanket insulation, rigid foam board insulation, and loose-fill insulation. Each type of insulation has its own R-value and should be chosen based on the climate, moisture control, and basement configuration.

Liquid Foam Insulation

Liquid foam insulation can be applied through spraying, foaming, injection, or pouring into place. The materials commonly used include polyurethane, polyisocyanurate, phenolic, and cementitious. Due to its ability to fill tiny cavities, it provides twice the R-value per inch compared to traditional blanket insulation.

Benefits of Basement Wall Insulation

The primary advantage of insulating basement walls is the reduction in energy costs. However, the amount of savings depends on several factors such as local climate, heating system type, fuel expenses, and the lifestyle of the occupants. Proper installation is crucial for optimal thermal performance, which is why hiring an experienced contractor is recommended. The most cost-effective way to insulate an existing basement while minimizing moisture issues is through a combination of rigid foam insulation and an insulated frame wall assembly.

Airflow is critical. The foundation must be able to disperse moisture into the basement to allow it to dry properly. Restricting airflow can trap moisture, and using a true vapor barrier to prevent moisture from entering the basement can trap moisture between the insulation and the wall. If the insulation is installed on a wood wall frame and enclosed in a vapor barrier like polyethylene sheeting, moisture will be trapped inside, damaging both the insulation and the wood frame.

Now that you have a basic understanding of insulation types, tools, materials, and benefits, you should be ready to start your basement wall insulation project and enjoy energy savings every year. Check out the links on the following page to learn more.

External vs. Middle Insulation

Using 2 to 3 inches (5.08 to 7.62 cm) of exterior foam basement wall insulation with an R-10 value in homes did not result in significant savings compared to using insulated concrete forms (ICFs) insulation with an R-2 value. For instance, a 1,500-square-foot (139.3-square-meter) home in the Midwest could save approximately $400 per year in natural gas heating costs using exterior foam insulation at an R-10 value. However, using ICFs with an R-2 value would save about $450 a year [source: U.S. Department of Energy].

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This is a list of online resources that provide information on basement insulation. The list includes Ask the Builder, Building Science Corporation, The Encyclopedia of Alternative Energy and Sustainable Living, The Home Improvement Web, Insulation Contractors Association of America, Minnesota Department of Commerce, This Old House, and the U.S. Department of Energy. Each resource can be accessed through the links provided.


1. What is the purpose of insulating basement walls?

Insulating basement walls is important in order to regulate the temperature of your home and prevent energy loss. Uninsulated walls allow heat to escape in the winter and enter in the summer, making your home less comfortable and more expensive to heat and cool.

2. What are the different types of insulation that can be used?

The most common types of insulation used to insulate basement walls are fiberglass batts, foam board insulation, and spray foam insulation. Each type has its own advantages and disadvantages, depending on the specific needs of your home and budget.

3. Can I insulate my basement walls myself?

Yes, you can insulate your basement walls yourself, but it is important to follow the manufacturer’s instructions and take all necessary safety precautions. If you are unsure about your ability to complete the job, it may be best to hire a professional.

4. How do I prepare my basement walls for insulation?

Before insulating your basement walls, it is important to clean the walls thoroughly and repair any cracks or leaks. This will ensure that the insulation is effective and prevent any moisture issues from arising.

5. How do I choose the right insulation for my basement walls?

The right insulation for your basement walls depends on a variety of factors, including the climate you live in, the age of your home, and your budget. Consulting with a professional can help you determine the best type of insulation for your needs.

6. How much insulation do I need to use?

The amount of insulation needed depends on the size of your basement and the type of insulation used. Consulting with a professional can help you determine the appropriate amount of insulation for your specific needs.

7. Can I use insulation to soundproof my basement?

Insulation can help to reduce noise transmission between rooms, but it is not specifically designed for soundproofing. If soundproofing is a concern, it may be best to consult with a professional or use specialized soundproofing materials.

8. Will insulating my basement walls prevent moisture issues?

Insulating your basement walls can help to prevent moisture issues by regulating the temperature and reducing the potential for condensation. However, it is important to address any existing moisture issues before insulating, as insulation can trap moisture and cause further damage.

9. How long does it take to insulate basement walls?

The time it takes to insulate basement walls depends on a variety of factors, including the size of your basement and the type of insulation used. It can take anywhere from a few hours to a few days to complete the job.

10. Will insulating my basement walls increase the value of my home?

Insulating your basement walls can increase the value of your home by making it more energy efficient and comfortable to live in. It can also be an attractive feature for potential buyers, as it can save them money on heating and cooling costs.

11. How often should I replace insulation in my basement walls?

The lifespan of insulation depends on a variety of factors, including the type of insulation used and the conditions it is exposed to. It is generally recommended to replace insulation every 10-15 years to ensure that it is still effective.

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