Homes in colder climates lose a large amount of heat through the walls of the basement. Energy efficient basements can help prevent this heat loss while saving money spent on energy bills. If you know how to insulate basement walls, you can make the basement of your home more energy efficient by keeping it warmer and drier than an uninsulated basement.
Step
Method 1 of 3: Selecting the Insulation Type
Step 1. Choose an R value
The R value is a measure of how well the insulation works at reducing the flow of hot or cold air. A higher R value per inch of thickness indicates better insulation. The required R value depends on the climate in which your home is located and on how well you want your home to be insulated.
- For example, if you live in a warm climate, you'll want a minimum value of R-30.
- Cold climates require a minimum value close to R-60.
Step 2. Evaluate your insulation options
The R value will help you choose the level of insulation you will need. There are many types of basement insulation. The three most popular types of insulation are batt and roll (blanket), loose-fill, and sprayed-foam.
- For blanket or batt and roll insulation, simply nail or screw the insulation to the wooden frame. Typically, this blanket insulation is available in standard wall frame sizes.
- For loose-fill insulation, install drywall on the posts before adding the loose-fill insulation.
-
Spray foam insulation is the most energy efficient option for insulating basements. You may need to rent equipment to insulate the basement with wet sprayed cellulose. These kits are available at major hardware stores. Spray foam can be either open cell or closed cell.
- Open cell means that there is air in between the many bubbles produced by the spray foam.
- Closed cells, although slightly more expensive, are filled with non-air chemicals which are more efficient as insulation.
Step 3. Consider additional treatments for your insulation
Additional treatments can help protect the insulation from moisture and can make it more fire resistant.
- Faced insulation uses a vapor barrier that controls the movement of moisture between walls.
- Unfaced insulation does not have a vapor barrier, but you may not need one, for example if you are installing insulation over an existing installation or if moisture control is not required.
- Flame retardant coatings are often required, as many types of insulation release toxic gases when ignited. Check local building codes to see if this coating is required or not.
Method 2 of 3: Installing Hybrid Insulation Made of Rigid Foam and Fiber Glass
Step 1. Frame the walls with wood
(If you are planning to install a vapor barrier, consider that section now as certain steam insulation is between the wooden frame and the concrete wall). Consider using composite decking on the basement floor for extra moisture protection, or you can use pressure treated 2x4 baseboard. Otherwise, use standard wall framing techniques to build the wall posts. Use a height level to estimate the height of the framed wall, and leave a gap of about one inch (± 2.5 cm) between the pile wall and the cinder block to provide plenty of room for insulation.
Step 2. Select the insulation board
Boards can include molded expanded polystyrene (MEPS), extruded expanded polystyrene (XEPS), and urethanes such as polyurethane. Usually, for basement walls, XEPS is recommended because XEPS is sturdier and has a higher R-value than MEPS, which is the least expensive option but not as powerful as XEPS. Another option is urethane, which is strong and is often used with plywood. A board thickness of at least 1.5 inches (± 3.3 cm) is usually recommended.
Step 3. Cut the board and place it in position
Cut the boards to fit between the posts from side to side and against the concrete wall. Use constructive tape to attach the boards to the wall and apply a caulk or foam that expands around the edges of the boards and against the posts. Remember to install the board from the base all the way up to the wall.
Step 4. Tighten the joints of the boards
This is an important part of tightening the vapor barrier. Examples of sealing materials include adhesive tapes such as Tyvek Tape and Dow Construction Tape or canned foams such as Great Stuff. Seal joints or gaps between boards and between boards and posts or concrete.
Step 5. Install fiberglass
Fiberglass will be placed in the wall cavity created between the frame and the foam insulation board. Nail or fix with reel staples or fiberglass sheets to the wooden frame. A nail gun can be an efficient way to nail the roll or sheet. Remember to be careful doing this, and wear protective eyewear and gloves.
Step 6. Add a vapor barrier
This is an optional step, but some people enjoy adding a vapor barrier between the fiberglass and drywall. This is especially recommended if the thickness of the initially installed foam insulation board is less than 1.5 inches (± 3.3 cm). Concrete or block walls absorb moisture like a sponge, and will periodically release moisture toward the drywall, posts, and ribs. The steam insulation helps prevent moisture that causes mold to grow on the insulation, which can be very expensive to repair.
Step 7. Cover the insulation with a wall surface
Whether you're using batt and roll insulation, loose-fill insulation, or spray foam insulation, don't leave your insulation uncovered. You have many options for wall surfaces. Drywall is commonly used to cover basement insulation, but if aesthetics isn't a concern, you can also cover the insulation with plywood.
- Cover the insulation with drywall. Usually, drywall is a 4'x8' (±10 cm x 20.3 cm) sheet so you will need to measure and cut the drywall to fit the wall. When hanging drywall, start at the corner. Prepare the posts, ribs, or fasteners by applying glue to the surface immediately before you plan to hang the drywall. Then, use screws or a nail gun to nail the drywall. Once all the drywall has been hung, mix the clay and apply it with a putty knife along the joints between the drywall panels and in the corners. Cover this area with drywall adhesive tape as well. After the clay is dry, smooth it with sandpaper and smooth each area that was given the clay.
- Alternatively, use plywood on your insulation. The plywood may need to be bent to cover the entire insulation. This can include laminating pieces of plywood, steaming, soaking the plywood, or cutting the kerf (i.e. grooves) and reinforcing the plywood using glue. Also, try to look for plywood without knots, especially in areas that will be bent.
Method 3 of 3: Installing Spray Foam Insulation
Step 1. Choose the spray foam you like
Spray foam insulation is more expensive than foam board and fiber glass insulation, but spray foam insulation may be preferable because it results in a higher R value. Remember, you can use open cells, closed cells, or a combination of both.
Step 2. Use safety equipment
At a minimum, you should wear disposable coveralls with hand and foot covers as well as a respirator. (Although a simple mask may be suitable for fiberglass fitting, you will need a respirator when handling foam). You'll also need a hood and protective goggles that fit tightly around your eyes and temples.
Step 3. Leave some space between the frame and the wall
Make sure the frame leaves about 4 inches (± 10 cm) of space on the wall. This allows you to spray continuous foam insulation behind a uniform 2x4 wallboard throughout the basement. As the foam expands and you continue to spray, check the walls to make sure the spray foam is uniform.
Step 4. Spray closed cell foam
Usually, spraying foam insulation is a job for a professional worker, but if you do it yourself, you will need the two main ingredients of closed cell insulation, often called components A and B. Use a heated hose to send the components through a mixing gun (chemical reaction). will start immediately after mixing), and spray onto the surface that needs to be insulated.
Spray about 2 inches (± 5 cm) on the wall. Check the applicable energy regulations, if any, but usually 2 inches (± 5 cm) on walls and 3 inches (± 7.5 cm) on rooflines. Check at specific points in various areas to ensure that the thickness of the foam is uniform throughout
Step 5. Remember to spray sparingly
Closed cell foam will expand to about 25 times its liquid size and form a moisture barrier. Since closed cell foam also has a higher R value than open cell foam, you'll get more insulation for less.
Step 6. Alternatively, use open cell foam or a combination of open and closed cell foam
If you plan on spraying open cell foam, which also expands heavily, insulate the trackboard and basement ribs first.
- At this point, you can save money by applying closed-cell foam right to the trackboard and ribs. Before spraying open-cell foam, spray a small amount of closed-cell foam on these areas. Try to seal the gap to strengthen the insulation. Then, spray open cell foam on the insulation area.
- Alternatively, you can apply putty or Great Stuff, which is a polyurethane-based insulating foam, on strip or rib boards. Again, try to form a seal to prevent air and moisture from entering through the gap.
Step 7. Spray open cell foam
Once the strip boards and ribs are insulated, you're ready to spray. Apply open cell foam in the same way as closed cell foam, with a heated hose and mixing gun. However, you may have to use a thicker layer of open cell foam because the R value of open cell foam is lower. Use an open cell foam layer thickness of about 3 to 5.5 inches (± 7.5 to 14 cm). Fortunately, open cell foam expands and fills the framing cavities better than closed cell foam. As a result, it will be easier to track the progress of the spraying.
Tips
- Check local regulations to determine whether or not you should add fireproof protection to the insulation. Even if not required by regulation, adding a fireproof coating can provide additional protection.
- Since the basement is connected to the rest of the house, basement ceiling insulation does not provide as much energy efficiency as basement wall insulation. Wall insulation provides the greater advantage of protecting your home from the temperature and humidity outside. Insulating walls is also easier and requires less insulation.
- If you are building a new home, ask the contractor about insulating concrete blocks or other forms of insulating concrete that can be installed during construction and provide added energy efficiency to the basement.
