How to Insulate a Basement: A Homeowner's Guide

Because dirt can be a good conductor of cold air, the chilliest part of your home in colder months is likely your basement. And when dropping temperatures encounter moisture in your basement, you're susceptible to mold and potential plumbing issues. Insulating every room in your house, even the basement, is one of the best energy-efficient tips for heating your home. Whether you've turned your basement into a living space or are using it for storage, you'll want to keep both cold and moisture out by insulating basement walls.

Basement wall insulation is different from the fiberglass variety used in the walls of other rooms in your home, primarily because fiberglass is more susceptible to moisture. While some types of basement insulation should be installed by professionals, there are others that ambitious DIYers with basic carpentry skills can place themselves. In this guide, we'll cover how to insulate basement walls yourself. Here's how to make this area of your home comfortable, dry, soundproof, and more energy efficient.

Types of Basement Wall Insulation

When deciding what type of insulation to use for your basement walls, consider the cost and effort each requires. Using all fiberglass insulation or a basement insulation blanket aren't good choices because they absorb moisture and create a breeding ground for mold and bacteria. There are three common types of basement wall insulation used by homeowners, each with a short list of pros and cons:

• Rigid foam boards: This type of wall foam is the most popular type of insulation due to its lower cost, water absorption, and ease of installation. However, it's better for wide walls and not for narrow spaces.
• Spray foam: When insulating basement walls with narrow spaces, spray foam is the preferred type. You can even use this expanding wall foam in combination with rigid foam boards for superior insulation. However, it's more expensive and more difficult to install.
• Injection foam: This can be the best choice when figuring out how to insulate walls without removing the drywall that's already in place. Unlike spray foam, injection doesn't expand, but it is slightly more expensive and just as difficult to apply as spray foam.

Whether you are insulating basement walls with rigid foam boards or spray foam, you have two options for securing the drywall over the insulation: furring strips or a 2x4 frame. If you're using rigid foam and furring strips, secure the strips directly to the rigid foam and then secure the drywall on top of the strips. If you are using spray, build a wall system out of 2x4s, spray the foam on the wall, fill the system with more insulation, and secure the drywall over the top.

Note: Leaving the insulation exposed on your walls is a fire hazard that violates most local building codes.

Pro tip: Using a wall system in combination with rigid foam board insulation will leave room for electrical wires and pipes. Using furring strips won't allow space for this unless you carefully cut and plan spaces for these systems.

Safety Gear

Some of the materials used in basement wall insulation can potentially irritate your skin or lungs while installing, so it's a good idea to use the following safety equipment:

• Safety goggles
• Gloves
• Long-sleeved shirts and pants
• Dust mask or respirator, like an N95 mask

Installing Basement Wall Insulation

1. Check for Moisture

Before beginning your installation, use a moisture meter tool to check the interiors of your basement walls for moisture. You can complete a visual inspection, but it's also a good idea to check using a moisture-detecting tool. If the walls are wet or moisture is seeping in from the outside, installing insulation over it will only create mold and mildew. If there is moisture, you may have to adjust the drainage in the ground around the basement, use fans or a dehumidifier to dry out the area thoroughly, and seal any cracks in the wall.

2. Insulate Tie Rods and Band Joists

Before you get to the actual walls, there's some minor basement floor insulation work to complete to ensure there are no gaps when installing wall insulation.

For wood floors: Using spray foam, insulate the band joists in the floor of your basement; they're the wood beams that make up the perimeter of your floor's frame. Place foam in any gaps or cracks in the wood where these joists meet.

For cement floors: Tie rods are pieces of rebar used in construction practices for older homes. They may stick up above the surface of the concrete foundation in the basement. Using a hammer, tap them down into the foundation until they're below the surface, then seal the remaining hole with cement.

3. Apply a Thermal Barrier

Some building codes require you to install a thermal barrier between the basement wall and the foam insulation of your choice. Whether or not your city or state requires it, a thermal barrier can help keep the room warmer and more soundproof and provide an easier, more even surface when insulating basement walls.

4. Install the Wall Foam

If you're using rigid foam boards, secure them to your basement's concrete walls with a foamboard adhesive. Place them vertically, not horizontally, and try to use a full strip of foam board when you can. Fit the edges of the rigid foam boards as flush as possible and seal any cracks between them with tape or adhesive.

If you're using spray foam for basement wall insulation, you'll first need to build and install the wall system, as mentioned earlier, and then fill the wooden frame with spray foam.

If your goal is to insulate your walls with injection foam to avoid removing drywall, drill holes in the drywall and inject the foam into them. After it dries, the foam seals the holes you've drilled.

5. Cover the Insulation

If you've used injection foam and already have drywall in place, you can skip this step. If you're using rigid foam and employing furring strips, place them side by side over the board and secure them with concrete screws using a drill.

If either spray foam or rigid foam boards and a wall system is your method of choice, attach the bottom of the already built frame of 2x4s to the concrete foundation concrete screws and the top of the frame to the ceiling joists. Then, carefully add more insulation between the studs of the wall system — you can use spray foam or layers of more foam boards but do not use fiberglass insulation.

6. Add Drywall Over the Covering

Again, you can skip this step if you use injection foam to insulate basement walls. Whether you've covered your wall foam with furring strips or a wall system, drywall will need to be placed over either. Like your insulation, make sure to choose drywall that is resistant to moisture, like greenboard. Then, secure the drywall sheets to the furring strips or wall system with drywall screws. Once the drywall is installed, place mesh or paper tape on the seams where the drywall panels meet, then mud and sand down the drywall for the final step.

7. Finishing Basement Walls

The final step is to finish the wall if desired. Apply a waterproof drywall primer, and after it dries, paint over the drywall panels you've installed with acrylic or another kind of water-resistant interior paint. That's it — you're done! And unless you end up with a flooded basement or experience another kind of disaster, your wall foam insulation should last 80 to 100 years.

If this list of steps for how to insulate basement walls seems a little too daunting, or you begin your installation, and it doesn't go as planned, don't hesitate to call a professional. As far as DIY home projects go, this one can be on the tougher side. If you do need an insulation contractor, be sure to find one who has the appropriate credentials, is willing to communicate with you frequently throughout the installation and has solid customer reviews.

While your basement insulation may not need to be replacedin your lifetime, your home's systems and appliances likely will. With a First American home warranty, you can enjoy peace of mind knowing you're covered when unexpected repairs or replacements arise. Get a free home warranty quote today.

The contents of this article are provided for general guidance only. First American Home Warranty does not assume any responsibility for losses or damages as a result of using this information.

Please be aware that if you disassemble a covered system or item, it can invalidate your home warranty or manufacturer's warranty.