Crawl Space Soil Gas
Click the link for additional information on a cat pee smell in the crawl space.
Crawl space encapsulation® is gaining ground in popularity across the United States and Canada. Regardless of its new growing popularity, some people have practiced caution, waiting to find out if this new technology really works before investing the thousands of dollars it takes to complete this home improvement. The good news is that most of the headaches and hiccups have been remedied. While positive progress is being made in most areas, we are still looking for solutions to address the issues of improper installation by contractors and price gouging.
Most recently, one of the largest speed bumps that we’ve successfully navigated around was identifying the cause of a mystery odor that has been forming, typically between 30 and 60 days, after some encapsulations. It was a mystery for obvious reasons, such as the primary fact being that encapsulations are supposed to stop and prevent most odor problems. So of course, when it came out that encapsulation appeared to possibly create a new odor problem, customers all around the country were naturally a bit upset, to say the least.
Our First Case of the “Odor”
The first documented instance of this issue reached us in the spring of 2009 via Walter, a contractor based in Memphis, TN. Walter was having a problem identifying the source of an odor in a crawl space he had encapsulated using the SilverBack® brand vapor barrier. The house was a new home, and the new owners of the home communicated to Walter that they were certainly not going to accept that odor.
After speaking with the homeowners about the issue, Walter called us up, informing us that the homeowners claimed that our SilverBack® vapor barrier seemed to be causing the terrible odor invading their home. Walter described the scent as being really bad, and though he found it hard to describe the smell, he said that it smelled very similar to cat urine. Our first thought was of the fact that the SilverBack® vapor barrier is completely inert and that there is no off-gassing or smell to the plastic. Walter was quick to accept this explanation, as he stated that he really didn’t believe that the odor was coming from the SilverBack®. Walter indicated that he’d passed this information along to the contractor who built the house, and then he and the contractor began working together to try and figure out the source of the odor problem.
We didn’t hear anything more from Walter about the issue until he called us again in October of 2009. Walter was clearly more frustrated on this call. This was due in large part to the contractor requiring him to remove the 20 mil SilverBack®, simply because the contractor was convinced it was causing the odor. After that, he had Walter install a 6 mil clear plastic from the local hardware store. However, within days of installing the 6 mil, the odor returned and was even worse than before, so the contractor then told Walter to remove it. After removing the 6 mil, the contractor unbelievably instructed Walter to install the 20 mil SilverBack® again! Upon reinstalling the SilverBack®, the odor lessened back to its original level of strength, which prompted Walter to reach out to us again. At that point, Walter, the contractor, and the homeowners were at their wit’s end and desperate for a solution.
Upon doing some investigating, we discovered that the home was in fact a new house, but it was constructed on an old foundation. It turns out that the foundation was actually formerly a basement and that the homebuilder had filled it in to make a crawl space. It was certainly an odd choice to make, but to each their own, right? But moving on, upon learning of the “remodel,” we spoke with Walter to learn where the fill dirt came from. Unsurprisingly, he didn’t have the answer to that, but he said that he was determined to find out.
A few days later, Walter contacted us and informed us that the contractor had refused to tell him where the dirt came from. After making several attempts to find out where the dirt came from, with no success, the reasonable assumption was made that the fill dirt was most likely not acquired through standard channels and that it probably came from a farm or a field somewhere. Given that we knew the odor was not coming from the SilverBack® barrier and we had confirmed there was no fiberglass insulation in the crawl space, it was all but assured that it could only be coming from one place: the soil under the SilverBack®. It also seemed the prime suspect, given that we had no information on its origin and that we were being deliberately kept in the dark about that origin.
The Solution
If the odor was in fact coming from under the barrier, as we were all but certain it was, then it was plausible that it was possibly a gas like methane. We suggested to Walter that he mitigate the air under the barrier as if the crawl space had a radon gas problem. We were aware that this smell was not radon because radon is odorless, but the radon mitigation process would nonetheless remove any soil gas in the crawl space causing the odor. After a quick rundown on how to set up the piping and a collection point, Walter went to work putting everything in place.
We reached out to Walter about a week after he implemented the mitigation process to find out if our theorized solution worked. It turns out, the odor was gone the day following his installation of the mitigation system. This was sweet music to our ears!
While this specific story provides valuable insights and it had a favorable result, does it qualify as a universal remedy for every unexplained smell in a crawl space? No, unfortunately it does not.
In the fall of 2010 we received a phone call from another SilverBack® installer complaining of the same thing. This caller was also from Tennessee, but this caller, Gary, was from Knoxville instead of Memphis. Gary had three “stinky” crawl spaces belonging to three very unhappy customers. He had tried everything except for removing the SilverBack® to remedy these problems. We told him about Walter’s experience and recommended that he try out the same solution.
Then at around that same time period, we received two additional phone calls about odor problems. Both of these cases were out of North Carolina. One of the callers was yet another installer out of Greensboro by the name of Greg, and the other caller was Bill, one of Moisture Loc’s customers in Charlotte. Greg, the installer, told us that he had five “stinky” crawl spaces and that his customers were complaining that the smell was so bad that they could not sleep at night. The Moisture Loc customer, Bill, told us that he 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.
Just as we did for Gary, we told Greg and Bill about Walter’s experience and suggested that they should consider deploying the same solution that worked for him. So Gary, Greg, and Bill each installed gas mitigation systems, and wouldn’t you know? Each of their odor problems was solved! That’s 10 crawl spaces with odor problems that were eliminated by installing a soil gas mitigation system. That’s a 100% success rate! Given those results, we are beginning to believe that soil gases are the definitive answer for all of the unexplained bad odors in crawl spaces. It is worth noting, however, that not every “vapor barrier” marketed for encapsulation is naturally odor-free; some contain additives that may lead to off-gassing. Given our awareness of this, we feel it is essential that homeowners stay informed about the specific materials being used in their homes.
