Do You Need Basement Insulation?

Winter can be especially cold in any basement, finished or otherwise. So with fall still in the air, now is the time to make this part of your home warmer and much more comfortable. Basement insulation helps make the floor above the basement feel warmer, and sealing drafts helps, too.

Before Old Man Winter arrives and settles in with all of his frigid baggage, give some attention to the lowest level of your home. Your heating bills will thank you, and so will your family.

Basement Insulation Includes Sealing Air Leaks

Air leaks or drafts can make a basement feel chilly. These leaks can happen around egress windows, doors, near the ceiling edges, or through foundation cracks. But with a can of expanding spray foam, you can seal up openings and keep the heat inside where it belongs.

Expanding spray foam borders on magic with how well it works. All you need to do is attach the thin, plastic straw to the can’s nozzle, shake the can, aim the straw at the crack, and squeeze the nozzle’s trigger. Thin foam flows through the straw into the crack, and it expands and hardens once it comes in contact with air in the room.

You’ll need to use caution with expanding foam. It’s polyurethane-based, which means you can’t easily wash it off your hands. So you’ll want to wear gloves and old clothing. Also, it expands to many times larger than its original size. If you apply too much, you’ll need to trim off the excess after the material has hardened. Finally, it’s best to use the whole can at once. Check for drafts throughout your home so you can fill them at the same time. After the can has been used once, it’s very difficult and sometimes impossible to reopen the nozzle.

Water Infiltration Causes Big Problems

Water infiltration is a basement’s worst nightmare. Unfortunately, it’s also one of the most common basement problems. Water seeping in through the walls can make the room feel colder, and it can also cause foundation cracks when temperatures drop. 

One common cause of water infiltration is very simple. If the ground around your house is flat, or if it slopes toward the foundation, water can’t run off like it should. The water will, given enough time, flow through the soil and find cracks where it can seep into your house. That's why it's important to grade the ground around your home to make it slope away from the house.

Water may also be a problem if you don't have gutters or if they don’t the direct water far enough away from the foundation. Adding a flexible hose connected to the bottom of downspout or a drain bed (shown here) under downspouts can help divert water away from the house.

If you still have water seeping into the basement after correcting the grade and downspout problems, you can use hydraulic cement to seal leaks from small cracks. For larger problems, you might need to call a pro with expertise dealing with basement water problems. You may need special drains installed, and there may also be some waterproofing methods that can help keep your basement dry. Waterproofing sealer applied on the interior side of basement walls and floors almost never works unless the source of the water is corrected first.

Walls Need Basement Insulation

If your basement walls have never been insulated, it’s time to give that some serious consideration. A basement that's primarily a utility space, such as for laundry and storage, needs insulation almost as much as a finished basement does. Surprisingly, insulation on a basement ceiling doesn't do much to help. It’s best to focus on basement walls instead.

There are two approaches to insulating a basement, depending on how the walls were constructed. You can frame out the walls and insulate them similar to the rest of the house (review the different types of insulation) or you can use rigid foam panels.

Rigid foam board insulation was practically born for insulating basement walls. At least it seems that way because it’s so effective. It’s lightweight, so one person can often do the job alone. Using a special adhesive that’s made for foam board insulation, you can glue the foam to the basement walls, and then seal all of the seams between panels using foam board insulation seam tape.

After foam board is mounted on the walls, nailing furring strips over the foam lets you hang drywall for a finished look. Furring strips are thin, narrow boards. You’ll need one across the bottom edge of the wall just above the floor and another at the top, and then more horizontal rows spaced 16 inches apart, from the center of one board to the center of the next. Installing furring strips this way gives you the proper spacing for fastening drywall. For more details on installing this type of baseboard insulation, watch this video from ThisOldHouse.com.

Egress Windows are Cold Spots

If your basement has egress windows, they are a major potential source of heat transfer and drafts. Covering these windows with heavy-gauge plastic sheeting can help eliminate drafts and hold more heat inside. Use clear or translucent plastic, and you won’t lose any light from the windows.

Before installing plastic, be sure all air leaks around the window frames are sealed with caulk or expanding foam. And if there are any cracks in the glass, have the panes replaced before attempting any other window weatherproofing.

Winterization saves you money in the long run. It protects your home, and makes cold months a lot more comfortable for everyone. Although attic insulation is a primary focus for most home owners, basement insulation helps, too.

With a few tools, a few more supplies, and a dedicated weekend, you can tackle most of the work needed to keep your home warmer and drier now, and all year long.

What steps have you taken to keep your basement draft-free and cozier for the coming cold season? We’d love to hear your homeowner stories to motivate other homeowners to take action now.