How to Insulate a Crawl Space

The details of insulating a crawl space under a house are basic but there are a few options from which to choose depending on your particular circumstances.

Insulating a crawl space under a house with a dirt floor can help improve the energy efficiency of your home and reduce your energy costs. Here is a video on how we took on this project of insulation a crawl space of a lake house we renovated.

Insulating Crawl Space Under House – step-by-step

The following steps address some points to consider when deciding to insulate a crawl space under a house that has a dirt floor. 

  1. First, determine the type of insulation you want to use. Options include fiberglass batts, foam board, and spray foam. Consider factors such as the R-value (a measure of insulation’s effectiveness), cost, and ease of installation when making your decision.
  2. Next, prepare the crawl space for insulation. Remove any debris or clutter from the area. If there are any vents in the crawl space, consider closing them off to help maintain a consistent temperature.
  3. Measure the dimensions of the crawl space to determine how much insulation you will need. Keep in mind that you may need to cut the insulation to fit around pipes, wires, and other obstacles.
  4. Install the insulation. If you are using fiberglass batts or foam board, you can install them using adhesive or mechanical fasteners. If you are using spray foam, you will need to hire a professional to apply it.
  5. Once the insulation is installed, consider adding a moisture barrier to the dirt floor to help prevent moisture from entering the crawl space. Options include a layer of plastic sheeting or a concrete sealer.
  6. Finally, seal any gaps or openings in the crawl space to help prevent drafts and further improve the energy efficiency of your home. You can use weatherstripping, caulk, or spray foam to seal these gaps.

That’s it! By following these steps, you can effectively insulate your crawl space with a dirt floor and improve the energy efficiency of your home.

Pros and cons of the different types of insulation

Here are some advantages and disadvantages of the different types of insulation that you can use to insulate a crawl space under a house with a dirt floor:

  1. Fiberglass batts:
  • Advantages: Fiberglass batts are relatively inexpensive and easy to install. They also have a good R-value and are resistant to moisture.
  • Disadvantages: Fiberglass batts can be difficult to work with and may require protective clothing due to the potential for irritation from the fibers. They also do not provide a good air seal, which can reduce their effectiveness.
  1. Foam board:
  • Advantages: Foam board is relatively easy to install and provides a good air seal. It also has a high R-value and is resistant to moisture.
  • Disadvantages: Foam board is more expensive than fiberglass batts and can be difficult to cut and fit around obstacles. It also requires adhesives or mechanical fasteners to install, which can be time-consuming.
  1. Spray foam:
  • Advantages: Spray foam provides a good air seal and has a high R-value. It can also fill gaps and cracks effectively.
  • Disadvantages: Spray foam is the most expensive option and requires a professional to apply it. It also has a strong chemical smell during application and may require ventilation to dissipate the odor.

Overall, the best type of insulation for your crawl space will depend on your specific needs and budget. It is a good idea to consider the R-value, cost, ease of installation, and any potential drawbacks when making your decision.

Add rock wool as an option

Rock wool is another type of insulation that you can use to insulate a crawl space under a house with a dirt floor. Here are some advantages and disadvantages of rock wool:

  • Advantages: Rock wool is made from melted rock that is spun into fibers, making it a natural and sustainable option. It is also fire-resistant and has a high R-value.
  • Disadvantages: Rock wool is more expensive than fiberglass batts and can be difficult to install due to its density. It also requires special cutting equipment and protective clothing due to the potential for irritation from the fibers.

Like other types of insulation, the suitability of rock wool for your crawl space will depend on your specific needs and budget. It is a good idea to consider the R-value, cost, ease of installation, and any potential drawbacks when making your decision.