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How to Remove Crawl Space Odors Under the Vapor Barrier

featured image_How to Remove Crawl Space Odors from Under the Vapor Barrier

Are you concerned about crawl space odors under the vapor barrier?

Have you recently encapsulated your crawl space and noticed odors under the plastic?

In this article, we will discuss how to remove crawl space odors from under the vapor barrier.

What Causes Odors Under the Vapor Barrier

Many companies will install a crawl space encapsulation vapor barrier over organic materials like wood from construction projects and even dead animals.

Taking time to remove these objects prior to installing the vapor barrier in your encapsulated crawl space will reduce odors.

Dying Plant Matter and Soil Gases Can Contribute to Foul House Odors

Some objects are immovable and can still cause odors like plant root systems that may die after vapor barrier installation and molds that grow in the soil. Also, soil gases like methane and other VOCs can also create unavoidable odors in the future.

Beware: If you are experiencing a cat pee odor in your home from the crawl space, that could be caused by the vapor barrier itself. What I am about to share below will not fix that problem.

Click here to learn more. Also, this article is not designed as instruction on how to install a radon mitigation system.

Steps to Remove Odors Under the Vapor Barrier

  1. Cut the plastic near the foundation wall and install a Radon Away Radon-T under the vapor barrier. Run a 3-inch or 4-inch sewer and drain or PVC pipe from the T and outside the crawl space through the foundation wall.
  2. Install the radon fan (soil odor fan) outside the crawl space onto the PVC.
  3. Place PVC on the top of the soil gas fan and extend beyond the roof line. Installation instructions are provided with the fan.
  4. Install a vent cap on the top of the PVC to prevent rainwater from entering the PVC pipe.
  5. Check out RadonAway's page "Reducing Radon in New Construction" for more information.

Directing the air from under the crawl space plastic to the outside of the home should address soil gas odors. This method is usually used after the crawl space encapsulation is performed and is a retrofit to correcting the crawl space odor problem.

If you know you have odor issues prior to installing the crawl space vapor barrier, we recommend installing a perforated pipe through the crawl space in addition to the steps above. The perforated pipe can then be attached to the Radon-T and will be even more effective.

Also, a crawl space foundation vent fan can address soil gases above the vapor barrier.

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Contact Crawl Space Ninja to Remove Odors In Your Crawl Space

Do you need help with crawl space encapsulation in Alabama, Georgia, Delaware, North Carolina, Tennessee, Kentucky, or South Carolina? If so, 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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About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.


  1. Kevin Cleary on December 18, 2021 at 1:19 pm

    Hi Michael,
    I can’t thank you enough for all your great resources materials you’ve put out over the internet regarding crawl spaces!

    I recently bought a house with a 3-ft height crawl space and a fairly serious drainage and groundwater issue in it. After installing a gravity drain under the footing, daylighting it outdoors away from the house and then about 80-ft of interior perforated sub drain on the inside of the crawl the water woes are history.

    However, after 18 years (house’s age) of water inundation, damage had been done to the structure below. After removing all the foul debris, wet insulation, sealing perimeter and under-floor air gaps on my own, I had a mold remediation contractor come in and get rid of the mold. They basically followed all the steps you take and they did an outstanding job. Well worth the cost.

    After that, I re-insulation the entire sub-floor, attached new foam board to bottom of joists, then did a full encapsulation on my own. I attached a 9 mil poly scrim to the top of the footing with roofing adhesive/mastic and then overlapped and taped all the barrier on top on the existing crawl space grade. I also sealed up there crawl space vents with therma-pain windows that can open from outdoors. Lastly I’m able to run a simple dehumidifier with a gravity drain so it can run anytime it needs to.

    It is super dry down there now, but I do have a slight odor starting to develop within the space? Sort of an iron like smell?

    I’m the northeast, I think I can manage with closing the crawl space two seasons a year and opening the vent windows the other two seasons without creating new or repeat problems. Leaving it open spring and fall will at least allow for air exchange.

    You think I’m getting soil gas odors within the space now?

    Thanks again man, your info had been awesome!

    • Michael Church on December 23, 2021 at 10:43 am

      Soil gas odors could be the cause of the odor and depending on where the home was built (ie. old industrial site) may be why it smells similar to iron. Couple long term solutions could be a small perforated pipe under the vapor barrier that leads to a radon type fan to move soil gases out before it has an opportunity to enter the crawl space. Or you could do a foundation vent fan to move odors out that are above the vapor barrier/below the subfloor and hopefully remove them before they enter the living space. I have even seen homeowners do both in extreme situations. If you feel the solution of opening vents in spring and fall is taking care of it then you have already found the solution. We appreciate your kind words and hope this information helps you. Thank you.

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