Indoor Air Quality/crawl space odor

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CrawlSpaceOdorToo wrote at 2009-12-24 03:01:43
To Mr. Nichols and Theresa.   I read your article on Crawl space ordor (uriney smell) with great interest.  It is exactly the same problem I have had with my encapsulation project done three years ago. (3-30-2007)   The smell you vividly describe remains to this day. IT is NOT mold.  I have had humidification all along, since my crawl space was encapsulated andkept the crawl space at 48-50% humidity.   Reputable contractor properly installed encapsulation and was stumped by the smell in our crawl space. Attempted all remedies that Theresa wrote about..and then some.. including sealing the subfloor openings again, and all duct work. The contractor opened the vents and then installed an electronic air cleaner for over 3 weeks to try to eliminate the smell.  I Have had visits by many contractors with no conclusions as to the source of the smell.  The smell, like yours, increases when it rains.. indicating that humidity levels play a big part. A month ago I had a service called AirAdvice (by HomeAdvice) do a one week sampling of the air in the house to determine what was going on.  They found  all to be normal EXCEPT chemical pollutants to be high in the crawl space.. and showed a direct corelation with humidity levels.  The chemical concentration was highest when humidity levels were the highest. The system could not identify the source of the chemical pollutants but the technician attributed it to the smell found in the crawlspace.  They suggested reducing humidity levels down below 40% (similar to winter situations when smell is less obvious).. Recently had my HVAC contractor do a system checkup and when he entered the crawl space he commented on the smell immediatley and said it was common in all the encapsulated crawl spaces he had been in, (Raleigh NC area) done with white reinforced poly.... and that his own house smelled the same (cat urine smell he called it).. and that the smell was coming from the Poly liner.  



So although not a solution to eliminating the smell, keeping the humidity level low is the only way to minimize the smell..  For what its worth, I will be installing a commercial grade dehumidifier for next summer to keep the humidity levels at 40%.  The current dehumidier (50pints per day).. freezes over when I attempt to keep it that low of a setting in the summer as it has no defrost cycle like the commercial units do and freezes over.  I'm not much help, but wanted to pass along my similar problems over the past three years, to let you know that you are not the only one with the problem...  The urine smell persists to this day in my crawl space..and it appears it comes from the poly itself (or some chemical it is emitting)..


CrawlSpaceOdorToo wrote at 2009-12-24 03:06:39
Follow up- My answer was cut short:



I'm not much help, but wanted to pass along my similar problems over the past three years, to let you know that you are not the only one with the problem...  The urine smell persists to this day in my crawl space..and it appears it comes from the poly

itself (or some chemical it is emitting)..


hammer wrote at 2014-06-03 18:45:31
I too have this problem with a sealed crawlspace smelling like cat urine in the Raleigh, NC area.  I've heard from some that the odor may be coming from the dura-skrim used to seal it and from others that the odor is from the soil.  I am about to have a radon mitigation system installed as my most recent test tested positive for Radon.  I will let you know if that is successful in eliminating the odor.


Matt Garrett wrote at 2015-02-12 00:36:14
I am a crawl space Tech and my past employers home was first sealed with the black reinforced back liner and months later his crawl space smelled like cat urine.  He never told his wife so he could do a test to see if it would ever go away.  3 years later it still hadn't and he said "Never tell my wife!!!".  We had to pull up several homes that had this liner on it and never went back to the black backed reinforced liner again.  

  I opened my own Seal Crawl company and only use 6 mil clear initially then a 10 mil white on top.  I tried one 20 mil layer but saw punctures on 6 month inspections after other contractors/homeowners visited the drawl space. But THE 2 layers totaling 16 mil never punctures.  I guess sharp objects slide on both layers and minimize punctures.   www.SealedSolution.com   I hope this helps.


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TJ Nichols

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Hello, I'd be glad to answer your questions on IAQ & other related issues!

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My approach is to treat the home as one system with individual working parts. Think (TEAMWORK). When one or more areas (PLAYERS) are failing or bad, it affects the whole system (TEAM) to operate less efficiently. I aim to address the problem, not just the symptoms, to offer better solution options.

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High School Grad (06/1991)(VA) EPA licensed & certified in Types I & II Refrigeration (04/1997)(MD)

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Have served tens of thousands of customers over the course of my career

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