What Kind of Insulation Should I Use in My Crawl Space?

What kind of insulation should you use in your crawl space? That depends on whether you are venting or closing the crawl space. Open or ventilated crawl spaces can be insulated differently than closed or encapsulated crawl spaces. Decide first which crawl space you will have before deciding the best crawl space insulation materials to use.

Best Vented Crawl Space Insulation Materials

When your crawl space is open or vented, it allows outside temperatures to freely enter. Even vents that open and close automatically can allow extreme temperatures into your crawl space. Because of this, floor insulation is recommended for open crawl spaces.

Types of Crawl Space Floor Insulation

Many contractors will install batt insulation like fiberglass or rock wool. We see fiberglass sub-floor insulation the most in our area. Some contractors will also spray foam the sub-floor. Since we encourage crawl space encapsulation over vented crawl spaces, we remove a lot of sub-floor insulation.

CAUTION! Spray foam insulation is almost impossible to remove. It can also trap moisture and mold. Many contractors will install spray foam insulation to cover wet moldy wood.

Best Encapsulated Crawl Space Insulation Materials

Crawl space encapsulation requires a different insulation approach. You can insulate the sub-floor of an encapsulated crawl space. Foamboard or insulation vapor barrier is the preferred choice of Crawl Space Ninja. Not just any foamboard will do and sub-floor insulation can still trap mold and moisture.

Foam board on crawl space foundation walls

Foundation wall insulation for the crawl space should be rated to touch the ground. This is why we choose EPS foamboard. It is a termite-resistant expanded polystyrene (EPS) insulation for all types of construction applications. InsulBarrier is another great product for foundation wall insulation in both crawl spaces and basements.

Do you need help fixing your crawl space or basement? If so, we can help. Please contact us to schedule your assessment. Also, let us know in the comments below if you’d like to suggest a future blog post.

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6 thoughts on “What Kind of Insulation Should I Use in My Crawl Space?”

  1. Doing research to do my crawl space that is directly open to conditioned and finished basement. I am reading that international code requires a thermal barrier such as drywall, wood, cement board to cover foam board on walls. How do you get around this requirement? Does the foam board you use have an UL fire rating that meets the code? Thank you

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