Crawl Space Soil Gas

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Additional Information on the cat pee smell in the crawl space can be found here-https://crawlspacerepair.com/blog/Cat-Pee-Smell-In-The-Crawl-Space


Crawl space encapsulation is gaining ground in popularity across the United States and Canada. Even with its new popularity some people have shown caution by waiting to see if this new technology really works before investing into the thousands of dollars it takes to complete this home improvement. The good news is most of the bumps have been ironed out. We have yet to find a way to stop price gouging and contractors installing it improperly, but everything else is improving.

One of the bumps that has been fixed, most recently, is a mystery odor that appears after the encapsulation, somewhere between 30 to 60 days after. It was a mystery for obvious reasons, the encapsulation was suppose to stop the odor problems. So when it turned out that it seemed to create a new one, well customers nationwide were a bit more than upset. This problem first hit my desk in the spring of 2009 and the call was coming from Memphis TN. One of our contractors there was having a problem with an odor in a crawl space he encapsulated with the SilverBack™ brand vapor barrier. This house was a new home and the new owners were not accepting this odor.

Here’s what happened-

I get a call from Walter complaining that our SilverBack™ vapor barrier seemed to be causing an odor. He said it was hard to describe the smell, kind of like cat pee, it was terrible. My first reaction was the SilverBack™ vapor barrier is completely inert and there is no off gassing or smell to the plastic. Walter was quick to accept this explanation as he also believed it was not coming from the SilverBack™. As I understand, Walter relayed this information back to the contractor that built the house and they continued their attempt to figure out this problem.

I heard nothing more until October of 2009 when Walter called again, this time with much more frustration. As it turns out the contractor required him to remove the 20 Mil SilverBack™ (because he was convinced that was causing the odor) and install a 6 Mil clear plastic from the local hardware store. Within days of installing the 6 Mil, the odor was far worse than before and the contractor had Walter remove it. Believe it or not, the contractor then had Walter install the 20 Mil SilverBack™ again. With the second install the odor receded to the original complaint level which in turn caused Walter’s second phone call to me. At this point Walter, the contractor and the homeowner were desperate for a solution.

Upon further investigation I found out this was a new house but built on an old foundation. To be more exact, the foundation was a basement but the home’s contractor filled it in to make a crawl space. I know, I don’t get it either. Once I found this out I quizzed Walter on where the dirt came from. Of course he didn’t know but he was off to find out.

Walter called me a few days later with information, the contractor would not tell him where the dirt came from. To make a long story short, after several attempts at trying to find out where the dirt came from, I made a reasonable guess that it was not acquired through standard channels. My guess was that it came from a farm or a field somewhere. Since I knew the odor was not coming from the barrier and there was no fiberglass insulation in the crawl space, it seemed it could be coming from only one area; under the SilverBack™. It also seemed the dirt was the odd man out in this situation by being the unknown.

The Solution-

If it was coming from under the barrier then I thought maybe it was a gas like methane. I told Walter to mitigate the air under the barrier as if the crawl space had a Radon Gas problem. He and I both understood this was not Radon because Radon does not have an odor, but the process would remove any soil gas that was under there causing an odor. After a quick run down on how to set up the piping and a collection point he was off to put it place.

I called Walter after about a week to find out the outcome of my theory. Turns out the odor was gone the day following his installation of the mitigation system. Ahh, music to my ears.

Good story, but is that enough to call it a solution to every mystery odor found in a crawl space? I think not.

In the fall of 2010 I received a phone call from another SilverBack™ installer complaining of the same thing, also from TN but from Knoxville this time. Gary had three “stinky” crawl spaces with three upset customers. It seemed he tried everything, but taking out the SilverBack™ to remedy these problems. I told him the story about Walter and that he should try the same solution.

At about the same time I got two more phone calls about this problem, both from North Carolina. One of them was yet another installer out of Greensboro and the other was an customer of Moisture Loc in Charlotte. The installer had five “stinky” crawl spaces and his customers were complaining that they could not sleep at night the smell was so bad. The homeowner had everyone from indoor air quality professionals to HVAC contractors to the company that installed the barrier at his house trying to figure out where the smell was coming from.

Like Walter and Gary, I told Greg (the contractor from Greensboro) and Bill the homeowner from Charlotte the story about Walter and that they should use the same method to fix their problem. Gary, Greg and Bill each did and it solved their problem as well. That’s 10 crawl spaces with 100% success, now I’m thinking it’s the solution to every mystery odor in a crawl space. *Note- not all “vapor barriers” sold for crawl space encapsulation are odor free; even additives can cause off gas odors. It is very important to know what products are being installed in your home. Ask for the SilverBack™ brand crawl space vapor barrier by name, its guaranteed not to cause odor.

If you have any questions on how this process is done please feel free to contact us at 248.960.8870 or on the web Crawl Space Repair