How To Properly Insulate Your Home’s Foundation

An insulated foundation can help keep your home at a comfortable temperature while reducing energy bills. Proper insulation can help prevent air infiltration, keep moisture out of your crawl space and basement and reduce the likelihood of mold growth. Here’s a step-by-step guide on how to properly insulate your home’s foundation.

Determine the insulation type you need

The type of insulation you use will depend on your climate and whether you have a crawl space or basement. For a crawl space, consider using insulation with a vapor barrier. This will prevent moisture from entering your crawl space and provide a barrier between your living space and the cold ground. For a basement, use unfaced insulation that’s rated for exterior use.

Choose the right insulation material

Common materials used for foundation insulation include:

  • Fiberglass
  • Cellulose
  • Rigid foam
  • Spray foam

Fiberglass insulation is affordable and easy to install, but it’s not the best insulator for foundations. Cellulose is an eco-friendly option, but it can absorb moisture. Rigid foam provides the highest R-value per inch of any insulation material and can be used in crawl spaces and basements. Spray foam provides an airtight seal and can be used in hard-to-reach areas, but it’s expensive.

Prepare the foundation walls

Before installing insulation, make sure the foundation walls are clean and free of debris. Fill any cracks or gaps with foam sealant. If you’re installing insulation in a crawl space, make sure there’s proper drainage to prevent standing water.

Install the insulation

Cut insulation to fit the length of the foundation wall. Hold the insulation against the wall with the vapor barrier or facing towards the living space. Secure the insulation in place with adhesive or insulation hangers. Make sure to leave a small gap between the insulation and the top of the wall to allow for ventilation.

Seal any gaps

Seal any gaps between the insulation and the foundation wall with foam sealant or caulk. This will prevent air leakage and moisture from entering.

Finish up

Once the insulation is installed, cover it with a protective sheathing, such as plywood or paneling. This will protect the insulation and provide a finished look. If you’re insulating a crawl space, make sure to add a vapor barrier to the floor.


Proper insulation is essential for a well-ventilated and energy-efficient home. Foundation insulation can help prevent moisture from entering your crawl space or basement, reduce energy bills and keep your home at a comfortable temperature. Determine the right insulation type for your climate and choose the right insulation material. Prepare the foundation walls, install the insulation, seal any gaps and cover it with protective sheathing. By following these steps, you’ll have a properly insulated foundation that will benefit your home for years to come.

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