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Odor from Crawl Space

56K views 68 replies 18 participants last post by  beenthere 
#1 ·
Thanks in advance for anyone who can help! :thumbsup:

I purchased a house in central NC at the end of January 2012. During home inspection, we discovered a mold problem on the floor joists. We had a professional company come in and treat, kill, clean, etc. the mold. We also had a conditioned, sealed crawl space installed. The installer used a 20 mil vapor barrier and Thermax(TM) board insulation for the walls of the crawlspace. There are vents and returns along the main trunk line as required by code. The installer placed a humidity monitor in the crawl space that I can check and everything seemed be correctly done.

Now for the rest of the story and my reason for posting...

The next three days after the sealed crawl space was installed was horrible inside my house. There was an extremely strong odor like an earthy, musky smell. The installer thought that it was off-gassing from the materials in the crawl space and possibly the moisture that remained. "Give it a week."

A week goes by and the odor remained. I then placed a squirrel fan at the crawlspace door blowing out. The fan remained for about 5 days and the smell seemed to lessen. The installer placed a dehumidifier in the crawl space and said give it a little while longer.

Two more weeks, the smell lessened more but still was noticeable. As it was an unusually warm March in NC, we moved our stuff in the house and opened the windows to air it out. The heat was off during this time. Meanwhile, the installer taped the crawl space vents shut and installed a vent fan blowing out of the crawl space. Over the next few weeks, the odor appeared to be getting better. However, when a cold snap came through, the windows had to be shut and the heat turned on. The smell returned. The installer made sure all HVAC ducts were taped, the vapor barrier was rechecked, and the floor vent boots were sealed with a puddy that hardens from the crawl space side of the boot to limit leaks into the house.

The smell is still very noticeable inside my house. If you go to the vent fan blowing out, the smell is much stronger due to the concentrated air blowing out of the crawl space. We have triple checked the floor joists and they are bone dry (no moisture problem there). The humidity levels inside the crawl space and house are normal if not a little on the dry side (around 30-40 RH). We cut a small place in the vapor barrier and checked the soil under it, it too is dry and does not smell out of the ordinary. The HVAC ducts have been fogged, cleaned, and the coils cleaned on the unit. There is not any standing water anywhere in the crawl space.

I am my wits end here! Here are the facts I can tell you:

1. The floor joists had mold on them before the sealed crawl space was installed but there was never any smell inside the house before the conditioned crawl space was installed.
2. The HVAC ducts remained after the cleaning of the mold and were not replaced.
3. The odor was the strongest 1-4 days after the install but still remains.
4. To the best of my knowledge, there is NOT a moisture problem in the crawl space.
5. We have tried HEPA filters and an Ozone generator inside the house but not in the crawl space.
6. The installer did a follow up air quality test and there was less than the average household mold or spores in the air.
7. The odor seems to be worse when the heat is turned on.
8. The vent fan outputs this strong smell whether the HVAC is on or off.
9. We have taken samples of the vapor barrier, Thermax, and floor joists; none of which seemed to produce a smell when placed in a container and allowed to heat up with outside heat.
10. I AM IN DESPERATE NEED OF HELP TO SOLVE THIS PROBLEM!!! :furious:

Thanks for taking the time to read, please let me know if you have had a similar experience or can offer any suggestions!

Gary
 
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#2 ·
#3 ·
Griffolyn
® 20 Mil Reinforced is a multiply laminate combining U.V. stabilized film with a high strength cord grid. It is specifically engineered to provide high strength and durability in a lightweight material.

Also my installer checked the crawl space today and thought the smell was similar to cat urine. It might be, I don't know. Could this be off or out gassing?​

 
#7 ·
Thanks for the replies, but I am sure that rodents are not the problem. We do not have a dead animal smell or any signs or rodents. The crawl space is sealed and conditioned but thanks for the suggestion. At this point, we are going to run the air condition this weekend to see if the smell goes dormant due to the cool temperature (i.e molecules slow down with cold and speed up in heat). If it does go dormant, then off gassing is most likely the culprit, if the smell remains, then the HVAC air ducts are getting replaced.

Please continue to post any other ideas or similar situations you may have. Thanks,

G Ollis
 
#8 ·
What did they use to treat the mold?

If not too extensive, you could paint the joists with Zinzer (sp) 123, or similar to block it completely.
Ever had a water leak in a bath/laundry, with water getting into the supply duct/register to mold on the debris there....

Gary
 
#10 · (Edited)
Is there any fiberglass ductwork in or around the mold remediation area that could have gotten wet from the mold clean up?

Did the company take an air sample right at a supply diffuser (vent) with the air handler running?

Did they sample for anything other than particles? Any gas detection sampling such as formaldehyde, VOCs or other?

Is the mold remediator also taking the air samples?

If yes, have you considered using an independent air monitoring firm?
 
#11 ·
Possible causes:

1. Caused by the work/materials done/added to your crawl space. Suddenly you go from no-smell to smell just as they finish the work.

2. You said that someone thought it was a urine-like smell. So, that's also a possibility.

If, when you explore around in the crawl, you find that the smell seems to be concentrated in one area, it's more likely to be of urine or dead animal origin.

If it smells the same everywhere, then that work you had done seems more likely to be the cause.

I have been dealing with a urine smell in my crawl for a couple of years now. I have a radon mitigation system in my crawl, plus new HVAC furnace/coil/ductwork. The smell started about a year or two after all that work - and seems to have had some rodent activity as the source.

I tried all kinds of stuff to eliminate the odor. It's mainly a problem now in the warm, humid summer months.

You can read all the details (with many pictures) here:

http://www.diychatroom.com/f2/bad-smell-crawl-space-76931/

Check out the second page, near the bottom, for a summary.

What helps me the most is hanging three bags of Earth Care’s Odor Remover near the place where the return air duct meets the HVAC equipment. The odor seems to be getting into the HVAC system at that junction, even though a smoke test reveals no hint of a leak. The bags suck up almost all of the smell before it can get into the HVAC system.

If you can keep the HVAC system from sucking the smell into your ducts, with these bags, maybe you can breathe a little bit easier.

Here is a link to the odor eliminator bags:

http://www.cleartheair.com/english/bundles/10/dead_animal_odor_eliminator/2.html

Good luck.
 
#12 ·
John W.

Thanks. I have read your post before. The smell did not start until after the work was done and the smell is all around in the crawl space, not a certain spot. The smell began immediately after the mold problem was addressed.

Thanks again.

G Ollis
 
#14 ·
G,

About replacing your ducting:

Have you opened the system, say at either end of your HVAC equipment, and sniffed inside, while the blower was off? If the smell in the crawl is coming from a compromised duct system, it would probably smell much worse inside the ducts than it does in the rest of the crawl.
 
#15 ·
#16 ·
Thanks for the reply. The crawl is conditioned and sealed. The vents I speak of are floor vents or the damper vents placed on the main trunk line of the HVAC. Hope that clears it up. There was insulation under the floor before the mold was treated. It is completely gone now. The only insulation in the crawl is called EcoBatt and it is stuffed above the outer walls above the Thermax.

Of note to all: I had a third party come in today to check everything out. Unfortunately he was not able to pinpoint anything that I haven't considered. He did say that the HVAC returns inside the house smell strong like the crawl. BUT...my installer has removed some of the duct lines and checked them and didn't notice a bad smell. Going in circles!!!

Thanks to all.
 
#18 ·
John,

There are two returns inside my house. My house is approximately 2200 sq ft. One thing I did not mention earlier is that I have a sunroom off the back of the house that was added on before we bought the house. The sunroom is heated and cooled by the same HVAC system. The sunroom does NOT smell. I also had the front porch, which is covered brick, checked. There is no smell under the front porch. I say all of this because it makes me think more and more that the smell was caused by something placed in the crawl during sealing, I just don't know what that is.

G
 
#19 · (Edited)
G,

It seems that way to me too.

They put something into, or did something to, your crawl space that is creating the bad smell.

But its confusing that the smell is not reaching the sun room.

That makes it seem like the smell is coming up through the floor of the main house everywhere, not just up from the supply registers in the floor of each room.

Is the smell worse in some room than in others? Maybe bathrooms, kitchen. laundry room - places where plumbing comes up through the floor.

Is the bad smell stronger at the supply registers in the floor (in your main house rooms) than it is elsewhere in those rooms? Is it more noticeable at those supply registers when air is moving through the HVAC system?

If you turn the HVAC completely off, including no circulation mode, so that no air is moving through the HAVC system - then open the windows until the air smells good - then close the windows - then, still keeping the HVAC off - how long does it take for the smell to come back inside the house? Does it come back quicker if you turn the blower, heat or cool on right after closing the windows?
 
#22 · (Edited)
Thanks in advance for anyone who can help! :thumbsup:

We also had a conditioned, sealed crawl space installed. The installer used a 20 mil vapor barrier and Thermax(TM) board insulation for the walls of the crawlspace. There are vents and returns along the main trunk line as required by code.

Gary
Gary,

Rereading your initial post, it finally sunk in that your HVAC ducting may have been modified to make your crawl space part of the conditioned space of your house. Sorry for being so slow on the uptake.

If the crawl and indoor air are freely mixing, by design, then the only way to get the indoor air to smell nice will be to find and fix the source of the smell down in the crawl.

In my case there is a bad smell in the crawl space that has, so far, resisted all attempts at eradication. But, I do have a "solution" of sorts as I am able to soak up that smell before it can be sucked into the HVAC system.

With a conditioned crawl, my "solution" won't work for you. But, you can keep it in your back pocket, as a last resort (revert back to separate crawl and indoor air).

Hope you are having luck finding and fixing the smell.


P.S.

Could the smell just be what the walls, floor and joists down there have absorbed from the crawl since the house was built? I know that even the space inside interior walls can smell bad. It seems like making the crawl ready to be part of the conditioned space should include covering up such surfaces with something like a really good stain/odor blocking primer.
 
#23 ·
I hope I don't jinx myself but...

The installer removed the EcoBatt insulation in the crawl on Monday afternoon. He placed a fan in front of a crawl space door to remove particles in the air due to the insulation removal. I went to the house today (we have been staying with my in-laws for a week now) and it was much much better. I had my wife run the fan on the HVAC system for 3 hours until I could go by to check it. At 5:30 today, the house did not smell hardly at all. Now I realize it could just be the fresh air in the crawl space with fan, BUT I went into the crawl and smelled in front of the fan and the smell is maybe 25% of what it has been. We HOPE the insulation adsorbed the remediation smell, off gassing, chemical, etc. and that is what the smell was. We are going to let it air out for a few days.

The ultimate test will be when the crawl door is closed with no fan. I will keep you posted.

G
 
#24 ·
Update...

The removal of the insulation "helped" with the overall smell BUT it is not the source of the odor. After three days without the insulation and a fan pulling air from the crawl, the smell remains in the crawl but not as strong. I attribute the not as strong simply to the fan being on 24 hours a day for the last three days. This weekend we are going to do an ozone shock to the crawl space and check it again on Monday.

FYI...the third party that checked my house two weekends ago is a friend of mine. He called me the other day and informed me that he was in a meeting with several colleagues and the general thought of those in attendance (who are remediation contractors and sealed crawl) is the vapor barrier is causing the smell due to a reaction with the soil under the house. They have found that the vapor barrier produces a smell in some crawls and not in others. Their opinion is that it has to do with the soil. If the ozone doesn't work, the v.b. is getting replaced.

I shall keep digging until I get to the bottom of this situation.

G
 
#26 · (Edited)
I have been in a few sealed crawls and have one in my house as well that was installed along with a geo thermal system. All the sealed crawls I've been in smell like cat pee and if there was a smell issue in the house the smell penetrated the living space by seeping through cracks in the flooring and walls where they sit on the sub floor. This especially in older homes that were not built up to the insulating standards now practiced in building. Also the smell will enter the house through incorrectly installed/sealed ductwork under the house.

Because of pressure every time the heat or air cuts on in the house it pulls minute amounts of under the house air up through small holes as mentioned above and this air then gets circulated throughout the house via air return system.

A fresh air box added to the ac/heat system will most likely help to mix accumulated - inside the house smelly air - with fresh air and make it not quite as noticable and also provide fresh oxygen into an otherwise sealed enclosed air system.

On my house the cat pee smell has lessened considerably over time ( sealed crawl installed Oct 2010 ) and is now not noticed in the house but can still be smelled underneath inside the crawlspace...
 
#27 ·
Thanks for the responses.

Here is an update...

Officially, we still do not know what is causing the odor. Unofficially, and what I believe to this point, I have been told that the mold after being treated and killed goes through a dying cycle. Evidently the mold gives off a gas as it dies and can take an undocumented amount of time to quit gassing. I have spoken to consulting firms, non-profit companies, etc. and the universal answer is to air seal all the leaks from the crawl to the living area and vent the crawl. That is what I have done to this point. The smell is much better in house and I think if we can get a good patch of warm weather I will be able to open up all my windows and air out the inside. I have not had a chance to do this yet after the air sealing. At least the house is livable now.
 
#28 ·
Sounds to me that it's probably the soil, and you need a better, or at least a different, vapor barrier on the floor. However, you could consider trying to fog the crawl with Concrobium. Buy a gallon and rent the fogger (both available at Home Depot), might cost a total of $50 and take a couple hours time max. The stuff is non-toxic to people/pets. I know your air tests say less than average mold currently, but any mold spores that may have been disturbed during remediation could have settled down and could smell bad now that you're sealed up. If it helps, you can assume the primer/sealer job may be worth doing (but you may not have to as Concrobium encapsulates the mold). If it doesn't help, at least you know there's no need to go through the added expense and labor of priming everything down there.
 
#29 ·
Interesting thread... I'm in the process of working up to sealing my crawlspace. One of the things I'm planning to do is vent the crawlspace to outside with bathroom fans. My intent is to end up sealed, but I have visible mold on my dirt and any time the crawl access is open dust gets into the living space. I was going to put in drainage, but I have a sump pit and no longer have flooding so at this point I'm guessing that the vapor barrier might do me more good sooner than later.
 
#32 ·
There is almost no smell at all from the product. It's a compound similar to baking soda. If I had to describe it I say there's almost, maybe, a temporary sort of "chalky" odor. But it goes away as soon as it dries

For about $20 for a gallon, and I think it was $25 to rent the fogger, I don't see how you can lose. At the least, it will deodorize the stale air down there, and it will coat every surface to cover any leftover mold spores. It does not leave much of a "coating", not slimy or anything, but supposedly encapsulates mold, killing it and preventing it from shooting out spores. I say supposedly because that's their advertisement, but I know it helped in my crawl. If this helps, you can probably assume if you plug in a dehumidifier down there and keep it dry, you may have completely solved your puzzle. If it doesn't actually solve your problem, it's not related to mold or mildew, but it will still help deodorize any bad odor to some extent.

http://www.concrobium.com/ <---check it out. My Depot had it in the paint chemical area, but if your's doesn't have it you can order online. Just google it because I don't think they sell directly.
 
#33 ·
Another update: My installer fogged the crawl space with the Concrobium to no avail. The smell inside my house is a minimum thanks to the air sealing in the crawl. However, the earthy, cat urine, plastic smell (depends on who the smeller is) remains. I think I can officially rule out any issues with the HVAC. I think I can also conclude that the smell is not caused by any mold in the dying stage. It has been 3 months since the remediation, plus as Pucks stated, the Concrobium should have ridded the crawl of smell if the smell was from mold. I have to revert back to off gassing from some material installed in the crawl while sealing it. At this point, I have two options. 1. Give it more time to go away on its own (we are currently using two crawl vent fans and a dehumidifier) or 2. Rip out the materials starting with the vapor barrier and see if the smell leaves with the materials.

As always, I apprecieate any comments or suggestions.

G Ollis
 
#34 ·
Gary,

Refresh me:

1. Do you still have crawl air deliberately mixing with indoor air via your HVAC system? I assume not, just checking.

2. What was done to the underside of your floor to stop the smell from getting up into the house? A single coat of a stain blocker won't do the job. If you apply multiple coats, till the surfaces are "as smooth as a baby's bottom" then you will block most smells. At least that's what I had to do to stop a mold smell that was actually on top of my old kitchen floor - before putting new laminate down.
 
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