Misconception: Vapor Barrier Will Insulate Crawl Space

Many crawl space contractors tell homeowners the vapor barrier will insulate the crawl space. We have homeowners ask if this is true and the short of it is no.

Vapor barrier is designed to inhibit moisture, not insulate (unless it is InsulBarrier). There are some insulation vapor barriers on the market and we use a great one, but most contractors are calling the plastic itself an insulator.

What is Insulation Vapor Barrier

If you want to retard moisture and insulate your crawl space, say hello to Insul-Barrier. This is a unique product we can install for you. Insul-Barrier is also available for the DIYer on our DIY Store.

Insul-Barrier is an R-8 moisture barrier that can be increased to an R-12 with proper furring of the foundation wall to create an air gap. The air gap behind the Insul-Barrier is a great way to add more R-value with just a bead of spray foam.

image of insulation vapor barrier

Is Vapor Barrier an Insulator?

To the best of my knowledge, crawl space vapor barrier does not carry an R-value unless it is Insul-Barrier. The crawl space companies that push vapor barrier as an insulation material are really doing a disservice to the homeowner by allowing them to believe insulation is not needed. The Department of Energy states that in addition to a properly installed vapor barrier you should insulate either the sub-floor or foundation walls of your crawl space. The best way to describe vapor barrier is a retarder of moisture, but not a valid way to insulate the crawl space.

Proper Crawl Space Insulation

If you are spending money on improving your crawl space, make sure you invest in proper crawl space insulation. This would include:

  1. Air sealing major sub-floor penetrations
  2. Rim joist insulation
  3. Air sealing and insulating the crawl space door
  4. Insulate and air seal the crawl space vents
  5. Air sealing major foundation wall penetrations
  6. Insulate and air seal around the HVAC foundation entry
  7. Air sealing and insulating the duct-work
  8. Insulate the foundation walls on a sealed crawl space
  9. Insulating the sub-floor on an open or vented crawl space
  10. Removing wet moldy insulation
  11. Do not reuse old insulation

Contact Crawl Space Ninja for Basement Waterproofing and Encapsulation

Please contact us to schedule your assessment to fix your crawl space, basement issue. 


Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, foundation repair, basement waterproofing, or controlling humidity in your crawl space?

If you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, or Kentucky, Crawl Space Ninja can help!


Also, let us know in the comments below if you have an idea for a new blog topic.

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