How To Insulate Crawl Space Walls

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If your crawl space isn't ventilated, insulating the walls may be beneficial. But how exactly do you do this? And what materials do you use to insulate crawl space walls? For your convenience, we have researched crawl spaces and the best ways to insulate the walls.

Here are the steps to insulate crawl space walls:

  1. Take moisture prevention measures
  2. Use a dehumidifier
  3. Lay down a vapor barrier
  4. Insulate the walls of the crawl space

Crawl spaces are known to create issues in your home or basement if they are not insulated, sealed, and/or waterproofed. This is especially true in areas that are prone to humidity or cold climates in the winter seasons. Continue reading to learn about how to keep your crawl space dry and more details about how to best insulate it.

A crawl space under the eves of a house showing old fibreglass insulation, How To Insulate Crawl Space Walls

Steps To Insulate Crawl Space Walls

It's especially important to insulate the walls of your crawl space if the space isn't ventilated. This can be a crucial aspect in terms of your home's energy efficiency if you live in an area with a cold climate.

Crawl space under typical American house

This is due to the fact that crawl spaces are often prone to leaks, which can cause you to have high energy bills as a result. By performing steps such as sealing air leaks, adding insulation, and creating vapor barriers, you can help to conserve your home's energy.

Things you'll need:

  • Rigid foam insulation
  • Utility knife
  • Crawl space moisture barrier material
  • Shovel and a rake
  • Flashlight
  • Portable saw
  • Construction adhesive or silicone caulk
  • Fiberglass batt insulation
  • Plastic

1. Take moisture prevention measures

Before installing insulation on the crawl space walls, it's important to remove any moisture that has accumulated in the space. To do this, use your rake and shovel to redirect any downspouts that may be forcing water to accumulate along the walls of the crawl space. Create soil banks so that they lead to the outside and back of your home instead of the walls.

This may be a bit laborious, so it's best to have an assistant help you. Afterward, use your flashlight to check the corners of the walls and ensure that there are no signs of leakage from the ceiling, walls, or other areas.

Check beneath any pipes that may be running in the basement as well as around the ceiling and wall joists. Look for any signs of moisture such as mold, smells of mildew, or wet spots.

2. Use a dehumidifier

If there is a moisture or leak issue in the basement, mitigate it before installing the insulation, as it can only worsen the matter. If there is this leakage coming from any pipes or joists, be sure to plug it up and seal the area properly. Afterward, place a dehumidifier in the space to get rid of any remaining humidity.

Check out this dehumidifier on Amazon.

3. Lay down a vapor barrier

Next, cut and measure your moisture barrier material and place it on the ground of the crawl space. Be sure to cut out holes for any pipes or post protrusions coming from the ground.

Make sure that the vapor barrier runs against the protrusions and goes all the way to the walls. Be sure to seal any seams with butyl tape. Next, install the barrier about 6 to 10 inches up the walls that will be insulated.

Find butyl tape on Amazon.

4. Insulate the walls of the crawl space

Next, measure and cut the rigid foam insulation pieces using your portable saw. Place the pieces between the joists on the crawl space walls, and if needed, apply latex adhesive for a secure fit. You'll want to create as few seams as possible—so the larger the panels, the better.

Be sure to seal the seams using the tape. If your crawl space walls only have masonry and no joists, you can simply line up the panels alongside one another. You can also use fiberglass and batts and line them up the same way.

Need a visual? Check out this video to see how it's done:

Should I insulate the walls of my crawl space?

Yes, it's generally recommended by HVAC technicians. Insulating the walls of your crawl space can help prevent moisture issues, pest problems, and other issues that can arrive from excessive humidity. Not to mention the insulation can help to increase your home's energy efficiency and potentially reduce your bills during the winter months.

What kind of insulation do you use in a crawl space?

Crawl space under a house

The most common insulation materials for crawl spaces are rigid foam panels and fiberglass batts or rolls. The reason for this is that these insulation types are easiest to install, as you only need to cut them to size and place them on the wall or between the joists.

You can also use foam cellulose insulation if you have joists on the crawl space walls. However, installing this will be extremely difficult, as there is typically little space to maneuver inside of crawl spaces, meaning that the sprayer for this insulation may prove difficult to use in such a tight area.

What is the best way to insulate a crawl space with a dirt floor?

Crawl space under typical American house

The best way to insulate a crawl space with a dirt floor is to use fiberglass or rigid foam insulation in addition to a moisture barrier. The moisture barrier will be placed on top of the dirt floor to prevent excessive moisture from accumulating inside the crawl space. This encapsulation method is usually done with polyethylene plastic at least 20 millimeters thick.

The barrier is typically sealed with butyl tape and runs up alongside the walls of the crawl space for complete encapsulation. Before installing the insulation and vapor barrier, it's essential to first double-check the crawl space for leaks from pipes or upper floors.

If not, you may find that the insulation is riddled with mold and mildew within a few weeks or months after it's been installed. If you repair the leak, be sure to dehumidify the crawl space before installing the vapor barrier and insulation. It may even be a good idea to keep one in the area if you've struggled with humidity issues in the past.

Is a vapor barrier required by code in a crawl space?

Yes, crawl spaces must be covered by a Class 1 vapor barrier. The barrier must overlap by at least six inches, and it must be sealed on all corners. Also, the barrier must be run along the walls of the crawl space at least six inches up.

Depending on your location, you may also have certain building codes for garden drainage and foundation requirements. So it's best to check with your local government to ensure that you are insulating your crawl space properly.

Wrapping Things Up

It's always best to consult with a home contractor on the best way to insulate your crawl space, as every home's crawl space will be different. Not only can you determine whether or not it's a project that you should take on, but you can also learn more details about how to keep humidity levels in your crawl space low, especially during the colder months.

We hope this post has helped explain why insulation and vapor barriers are essential in crawl spaces and how to install the insulation on the walls should you choose to do it yourself.

Before you go, be sure to check out these other posts:

Heil Furnace Leaking Water – What To Do

Can A Pellet Stove Run Without Electricity?

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