How to Insulate Your Basement

If you're insulating your basement, use this guide. Find out how insulating your basement can allow you to utilize it as another bedroom or living room.

A finished basement can add hundreds of square feet of livable space to your home, but in order to finish your basement properly, you need to insulate it. Even if you don’t plan on finishing your basement completely, insulating it can substantially lower your heating and cooling costs because it slows heat transfer through your masonry foundation walls.

If you don’t know how to insulate a basement, you’re not alone. Insulating basement walls is a big job, but it’s definitely one you can do yourself, maybe with the help of a friend or relative. Follow this step-by-step guide to get the job done right.

Choose Your Insulation

Before you start insulating your basement, you need to decide what kind of insulation to use. This article discusses how to insulate a basement using a combination of rigid foam insulation boards and fiberglass batting, but there are other options available.

You could choose loose-fill cellulose insulation, which would require you to install the studs and drywall and then fill behind the drywall with loose-fill insulation. This type of insulation may be less effective than fiberglass batting or spray foam because the loose fill could settle to the bottom of the space between the studs. Spray foam insulation is another option, but it should be installed by professionals.

When choosing insulation, consider its R-value, which is a measure of how effectively the insulation reduces heat exchange. In warm climates, an R-value of at least 30 should be sufficient, but in colder climates, an R-value of at least 60 will be necessary. For this tutorial, buy a rigid foam insulation board, like molded expanded polystyrene (MEPS) or extruded expanded polystyrene (XEPS). XEPS is best for a basement wall, since it’s stronger and has higher R-values. The board should be at least 1.5 inches thick.

Caulk Your Foundation Walls

Before you start installing insulation, go around your basement and use caulk and spray foam to plug any gaps or cracks between the masonry and the framing, as well as around any pipes or wires that penetrate through the masonry or framing.

Glue Foam Insulation to Foundation Walls

Glue your rigid foam boards to the foundation walls, cutting the pieces so that they fit tightly against the rim joists. Make sure you’re using glue designed for use with rigid foam insulation. Use smaller chunks of the foam boards to fill in gaps, and then caulk the seams.

Cut Top and Bottom Plates

Once you have installed the rigid foam insulation, it’s time to frame out the walls. Place a chalk line four inches away from the wall, going all around the basement. Then use two-by-fours to cut out top and bottom plates to fit. You can use composite decking material or weather-treated lumber for the bottom plates for added protection against moisture.

Install Blocking

You’ll need to install blocking between the first floor joists so you have something to attach the top plates to. Cut two-by-fours to the appropriate length to fit between the exterior wall and the first floor joist. Place them at intervals of three feet, going all the way around the basement walls.

Install Studs

Use a hammer drill and concrete screws to anchor the bottom plate into the floor, and screw the top plate to the blocks you installed in the last step. You should also toe-screw them into the rim joist through the rigid foam layer. Cut studs to the appropriate length and toenail them in at intervals of 16 inches.

Install Fiberglass Batts

Now that your studs are in place, install your fiberglass batt insulation. This type of insulation, also known as blanket insulation, comes in rolls. Make sure to use safety equipment, including gloves, a mask and goggles, when handling fiberglass insulation. Nail or staple the rolls to the wooden frame using a nail or staple gun. You can install a vapor layer on top of the fiberglass, although the rigid foam board installed previously should eliminate the need for this.

Cover the Insulation

Don’t leave insulation exposed in your basement. Cover the insulation with drywall or another wall surface. To install drywall, cut the sheets to fit your walls, and then hang them starting in the corner of the room. Apply the appropriate glue to the studs right before you hang the drywall, and then anchor the sheets by nailing them to the studs. Finish by applying drywall mud and tape to the seams. Once the mud dries, you can sand the seams smooth, prime the drywall, then paint it.

If you have drain cleanouts, ductwork, valves, breaker boxes and the like in your basement, you will need to frame around these features so that you can still access them. Most contractors will box out ductwork behind a soffit and frame out around cleanouts, valves, breaker boxes and other features in order to install access panels. While you’re framing out and insulating your basement, you may also want to go ahead and frame out additional walls to split up the space into multiple rooms. Research basement wall ideas beforehand so you know how your proposed walls will fit into your plans to insulate your basement.

An insulated basement can slash your energy costs and create a comfortable, livable space. Help protect the appliances, plumbing and other home systems in your newly finished basement with a home warranty from American Home Shield®. Contact us now to learn more.