# Bad smell in crawl space.



## John_W

Need help with a really bad smell in my crawl space.

About a month ago, when the summer heat and humidity first hit us (north Alabama), a corner of our crawl space started to stink of cat urine. I got a good UV flashlight and looked/sniffed every where – over the entire crawl space. I couldn’t find anything – no urine, no poop, no dead animals, and no mold – anywhere down there.

Next, I misted some odor remover (bacteria and enzyme type) on the tarp in that corner. That stopped the urine smell overnight – and it stayed gone.

Unfortunately, a different smell was ready for us the next day. It’s not a mold smell, a urine smell, a poop smell or a dead animal smell. It’s not a chemical smell. I guess it’s a cross between the usual earth smell in the crawl space and something like a weak dead animal smell. But it’s very strong.

I sprayed the tarp again with the odor remover and it just made the smell a little worse. The smell seems to be triggered by moisture since on dry days, it is not as bad. I pulled the tarp out of the crawl space. It stinks a lot, especially when it’s damp. The smell under the house is still strong though, even with the tarp gone. 

I pulled one of the batts of insulation out from between the floor joists. When dry, it has a slight odor. After I misted it with the odor remover it started to stink just like the tarp. On the other hand, the empty space between the joists, where that batt used to be, smells good now – just a nice wood smell.

The smell is only present in the south west corner of the crawl, pretty much limited to the area originally covered by the tarp. I put the gray tarp over our radon barrier, in that corner of the crawl, to protect the barrier from damage. That’s a high traffic area – between the door and the HVAC system. 

The entire crawl space “floor” is covered by the radon “barrier”. It’s about two years old. The barrier material is white on one side and black on the other, with built-in rip retarding thread. It is bonded to the walls with polyurethane adhesive. All junctions are overlapped by 12” and taped together. 

I’ve been blowing the smell out one of the vents with a box fan.

My next step will probably be to pull out all the insulation in that corner of the crawl.

Are there any other options? Is there a better odor removal product – maybe with a fogger that would get into every little crack?

Any ideas about what might have caused this smell?

Thanks.


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## John_W

*More pictures.*

Here are some more pictures.


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## Thurman

John, this may help you: The photos posted are similar to the underside of my home, but without the HVAC unit and water heater. I have only a high crawl space with a vapor barrier on the dirt floor. BUT: You are in N. Alabama and if I remember correctly you also have red clay soil such as we have here in S.W. GA. I had a similar odor problem just a couple of years after I bought this home, which had sat for sale for two years. We had an addition being done where I work and had a Geologist on site, so I asked if I could hire him to look at my lot. Thankfully he did it for a free home-cooked meal. Looking at my lot, from the street, it slopes from right front corner back to the left rear corner, with an elevation drop of maybe 18"--20". The Geologist told me that water would run through this red clay soil more-so than most other soils. Therefore, water was running through this soil, going through the concrete blocks of my foundation wall, and into the red clay soil under the home, being trapped under the vapor barrier (which was doing it's job) and causing a "musty/moldy" smell. He went under the home, dug a hole maybe 12" deep X 12" in diameter and it filled with water in less than five minutes--not good. He recommended an "Open French Drain" system at the inside perimeter of the foundation, which all led to a brick pit with a sump pump for discharge to the outside. This works--a lot, even in dry weather. The placement of a fan at one of the foundation vents was a big help also. I mounted a squirrel-cage type unit from a split A/C system to the foundation wall, on a timer for twice a day, and this has worked very well. No more musty/moldy odors in the house. David


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## John_W

Thurman said:


> John, this may help you: The photos posted are similar to the underside of my home, but without the HVAC unit and water heater. I have only a high crawl space with a vapor barrier on the dirt floor. BUT: You are in N. Alabama and if I remember correctly you also have red clay soil such as we have here in S.W. GA. I had a similar odor problem just a couple of years after I bought this home, which had sat for sale for two years. We had an addition being done where I work and had a Geologist on site, so I asked if I could hire him to look at my lot. Thankfully he did it for a free home-cooked meal. Looking at my lot, from the street, it slopes from right front corner back to the left rear corner, with an elevation drop of maybe 18"--20". The Geologist told me that water would run through this red clay soil more-so than most other soils. Therefore, water was running through this soil, going through the concrete blocks of my foundation wall, and into the red clay soil under the home, being trapped under the vapor barrier (which was doing it's job) and causing a "musty/moldy" smell. He went under the home, dug a hole maybe 12" deep X 12" in diameter and it filled with water in less than five minutes--not good. He recommended an "Open French Drain" system at the inside perimeter of the foundation, which all led to a brick pit with a sump pump for discharge to the outside. This works--a lot, even in dry weather. The placement of a fan at one of the foundation vents was a big help also. I mounted a squirrel-cage type unit from a split A/C system to the foundation wall, on a timer for twice a day, and this has worked very well. No more musty/moldy odors in the house. David


David,

Thanks for your comments.

It sounds like you get even more water in the crawl than we used to.

We also have red clay, on a sloping yard (we live on the lower slopes of a mountain) - with a drop of about 3 feet under the house itself - north to south. And we once had water running into the crawl space from under the foundation (in the high NW corner in the picture). 

About 15 years ago, we had a general contractor put in a deep french drain parallel to the high (north) side of the house, about 5 feet from the house, and slope the surface dirt strongly to channel rainfall to that same distance from the house. That work, plus a berm installed by the city, uphill from our property, really dried out the crawlspace. When I crawl around down there, I never find any soft spots. 

So, I'm pretty sure our current moisture source is mostly the water vapor coming in through the crawl space vents. It's bad enough to cause condensation on the main HVAC supply duct, and sometimes even on the insulation between the floor joists.

In fact, this year, after the first wave of humidity hit us, I found little pools of water on the radon barrier, near the north side vents, but uphill from the HVAC supply duct. It had rained inside the crawl space! 

After this odor problem is resolved, I'm thinking of sealing all the vents/gaps in the crawl space walls and using a 70 pint/day dehumidifier down there.


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## Wildie

At my place I had an odour problem in the crawl space that I couldn't figure out.

It turned out that the Transite (concrete) pipe leading to the septic tank had cracked inside the foundation wall.
There is no flex with Transite and settlement of the septic tank broke the pipe at its fulcrum point.
Replacement with ABS ended the problem.

Here in the north, we now seal the crawl space from outside air and make it part of the conditioned air space. Since I sealed mine, its been perfectly dry.

When hot, moist air enters a cooler area, it releases its moisture as it cools. This moisture pools and eventually causes mold growth.


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## John_W

Wildie said:


> At my place I had an odour problem in the crawl space that I couldn't figure out.
> 
> It turned out that the Transite (concrete) pipe leading to the septic tank had cracked inside the foundation wall.
> There is no flex with Transite and settlement of the septic tank broke the pipe at its fulcrum point.
> Replacement with ABS ended the problem.
> 
> Here in the north, we now seal the crawl space from outside air and make it part of the conditioned air space. Since I sealed mine, its been perfectly dry.
> 
> When hot, moist air enters a cooler area, it releases its moisture as it cools. This moisture pools and eventually causes mold growth.


Thanks Wildie,

Glad you found the problem.

Do the building codes up there allow sealed crawl spaces? It makes even more sense, down here, but I would be surprised if our codes allow it.

My initial plan is to use a dehumidifier, along with sealing the vents. I don't know if I need to put any conditioned air in the crawl. I have to be careful not to mess up the operation of the radon mitigation system. My radon contractor said that sealed vents plus a dehumidifier would not affect it's performance.

Baby steps.

I'm going under the house now to remove a bunch of smelly fiberglass insulation.


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## luvdairish

Your crawl looks a lot like mine. However, I don't have all the nice moisture control items (fan, vapor barrier, etc.). Given me some good ideas on how to setup mine! Thanks for sharing!! Best of luck :thumbsup:


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## Wildie

John_W said:


> Thanks Wildie,
> 
> Glad you found the problem.
> 
> Do the building codes up there allow sealed crawl spaces? It makes even more sense, down here, but I would be surprised if our codes allow it.
> 
> My initial plan is to use a dehumidifier, along with sealing the vents. I don't know if I need to put any conditioned air in the crawl. I have to be careful not to mess up the operation of the radon mitigation system. My radon contractor said that sealed vents plus a dehumidifier would not affect it's performance.
> 
> Baby steps.
> 
> I'm going under the house now to remove a bunch of smelly fiberglass insulation.


 If our codes don't require a closed crawl space, its certainly recommended by the building department.

I'm not familiar with the use of a radon shield. I would think that there would have to be a method of venting these gases. Do they vent to a roof stack?


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## Wildie

Here's a link to an interesting article about crawl space venting! 

http://www.askthebuilder.com/543-Crawl-Space-Vents.shtml


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## Gary in WA

http://www.advancedenergy.org/buildings/knowledge_library/crawl_spaces/pdfs/Closed Crawl Spaces.pdf

Check with local B.D. before changing from vented to closed: http://www2.iccsafe.org/cs/committeeArea/pdf_file/RE_06_64_07.pdf

Be safe, Gary


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## John_W

Wildie said:


> If our codes don't require a closed crawl space, its certainly recommended by the building department.
> 
> I'm not familiar with the use of a radon shield. I would think that there would have to be a method of venting these gases. Do they vent to a roof stack?


The pictures show the exhaust stack - inside and outside. The fan is in the box at the bottom of the stack on the outside. Inside the crawl, the PVC from the bottom of the fan attaches to a pipe, under the radon barrier, that runs the length of the crawl. That pipe has holes all along it that pull air from under the radon barrier.

This area has radon coming off uranium in the bedrock. Our house is built on the bedrock, or within a foot of it on all sides. People a few miles away, in the valley or flat lands, who have many feet of red clay under their homes don't have a radon problem.


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## John_W

*The inside picture is a before shot*

The inside picture was taken before the barrier was placed over the pipe and glued to the walls with polyurethane.


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## John_W

GBR in WA said:


> http://www.advancedenergy.org/buildings/knowledge_library/crawl_spaces/pdfs/Closed Crawl Spaces.pdf
> 
> Check with local B.D. before changing from vented to closed: http://www2.iccsafe.org/cs/committeeArea/pdf_file/RE_06_64_07.pdf
> 
> Be safe, Gary


Thanks Gary.

I don't have foam plastic insulation in the crawl. Are the sections of code in your second .pdf just for foam insulated crawl spaces?


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## John_W

Wildie said:


> Here's a link to an interesting article about crawl space venting!
> 
> http://www.askthebuilder.com/543-Crawl-Space-Vents.shtml


Thanks again.

I guess I will check with the local building department before I close the vents.


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## Wildie

John_W said:


> The inside picture was taken before the barrier was placed over the pipe and glued to the walls with polyurethane.


 Thanks for taking the trouble to explain John. Where I live, radon is unheard of, although there are area's within a days drive, where it is a problem.


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## John_W

*Insulation gone.*

The insulation is gone from the SW corner of the crawl. As you can see, we had some nut-eating critters hanging out up in/above the insulation.

We had a very cold winter this year. That must have driven the mice, or whatever, into our crawl space for warmth. While there, they must have peed quite bit. That is the likely source of our original urine smell.

They spent most of their time in two spots, both pretty close to the crawl door. That was their most likely entry point. There were minor caches in five or ten other places, farther from the door.

I have been intending to make a new, better fitting door - but haven't gotten around to it. For now, I just spayed some foam sealant in all the gaps, pipe openings, etc.

Does anyone know, based on the debris, what kind of critters we had?

The smell down there may have diminished a bit since I took the insulation out and cleaned out all the debris. I will give it another sniff tomorrow to be sure. But, I don't think its all gone.

There must be some smell stuck to the radon barrier. Its not the original urine smell, so I'm going to need some new odor remover ideas. The bacteria/enzyme solution stopped the urine smell with one application, but I'm wondering if it caused this newer smell.


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## Wildie

From what I see of the debrie, my guess would be small, brown squirrels. Chipmonks burrow in the ground and store their food down there also.
My neighbor had these squirrels get into his garage where he had his boat stored. They filled the boat with walnuts and chewed the canvas in many, many places. Very destructive, these little varmints!
My crawl space entrance is similar to yours and I sealed around jamb with expanding foam that was effective for keeping out the cold and the mice.
Rather than insulate the floors, as I see at your place, I insulated the foundation walls.
We have Roxul bat insulation readily available in Canada and I used this, held in place by insulation pins.
Roxul is fire rated and doesn't absorb moisture.
In your case, I would seriously consider insulating the foundation wall, rather than the over-head floor. Its much simpler to do. Using insulation pins, glued to the wall, just push the bats onto the pins. Press the vapor barrier over the insulation, and then use pin locks to keep everything in place.


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## John_W

Wildie said:


> From what I see of the debrie, my guess would be small, brown squirrels. Chipmonks burrow in the ground and store their food down there also.
> My neighbor had these squirrels get into his garage where he had his boat stored. They filled the boat with walnuts and chewed the canvas in many, many places. Very destructive, these little varmints!
> My crawl space entrance is similar to yours and I sealed around jamb with expanding foam that was effective for keeping out the cold and the mice.
> Rather than insulate the floors, as I see at your place, I insulated the foundation walls.
> We have Roxul bat insulation readily available in Canada and I used this, held in place by insulation pins.
> Roxul is fire rated and doesn't absorb moisture.
> In your case, I would seriously consider insulating the foundation wall, rather than the over-head floor. Its much simpler to do. Using insulation pins, glued to the wall, just push the bats onto the pins. Press the vapor barrier over the insulation, and then use pin locks to keep everything in place.


Wildie,

We have lots of gray squirrels and brown chipmunks here. The squirrels seem too big to fit the cracks I used to have. Still, with all the nut shells I found, squirrels were the first kind of critter that came to mind. 

I checked out Roxul. I can have it special ordered by the local Home Depot.

A picture or a link would help me understand how the insulation pins/locks work in conjunction with the Roxul and the vapor barrier.

I would have to figure out how to "interface" the vapor barrier on the crawl walls with the radon barrier. 

Do you "supply" any conditioned air to your crawl?


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## John_W

I'm on a different computer and logged in under a different user name. I need to switch this one over to John_W to be consistent.


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## Wildie

john-hvac-new said:


> Wildie,
> 
> We have lots of gray squirrels and brown chipmunks here. The squirrels seem too big to fit the cracks I used to have. Still, with all the nut shells I found, squirrels were the first kind of critter that came to mind.
> 
> I checked out Roxul. I can have it special ordered by the local Home Depot.
> 
> A picture or a link would help me understand how the insulation pins/locks work in conjunction with the Roxul and the vapor barrier.
> 
> I would have to figure out how to "interface" the vapor barrier on the crawl walls with the radon barrier.
> 
> Do you "supply" any conditioned air to your crawl?


 Unfortunately the place where I insulated the crawl space is at the lake. Its well over an hours drive and due to my wife's health condition, I have been limited on my visits there, this year!
However, I used the same method for my daughters basement and I'll try to get there and take a pic.
There is a discussion on this site already, that I responded to that you may like to read. http://www.diychatroom.com/f19/insulating-unheated-crawlspace-55293/

I had a new furnace and a/c installed in 2000 and I had the installers install a 6" duct to feed the crawl space and vent return to complete the circuit.

To interface the vapor barrier to the radon barrier, I would think it wise to provide a separation between the two. Pehaps mount a 1X2 on the wall, an inch or so above the radon shield. Then staple the vapor barrier to this.


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## Andy_39

*Cat urine smell att: John_W*

Hi John,
I'm new to this post and I've read your post about cat urine smell coming from HVAC when AC is on. I have a similar situation in my 1000 sq ft condo, air ducts/intakes running through the crawls space, vapor barrier installed on floor and up the walls, fiberglass batt insulation between floor joists, etc.. Whenever I turn on the AC you smell cat urine, when its off u don't. All the foundation vents are closed and no visible signs of moisture except some puddles like you saw but eventually dried up, some yellow in color. I placed odor eaters, damp eaters, lava rocks in the crawl to try to rid this smell. I wanted to ask if you came to a solution to rid the urine smell in your home?
I was thinking that if the insulation that covers the air ducts under the exterior foil covering gets damp or wet, might that smell of cat urine? BTW: my HVAC is a packaged unit that is outside.


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## John_W

Andy_39 said:


> Hi John,
> I'm new to this post and I've read your post about cat urine smell coming from HVAC when AC is on. I have a similar situation in my 1000 sq ft condo, air ducts/intakes running through the crawls space, vapor barrier installed on floor and up the walls, fiberglass batt insulation between floor joists, etc.. Whenever I turn on the AC you smell cat urine, when its off u don't. All the foundation vents are closed and no visible signs of moisture except some puddles like you saw but eventually dried up, some yellow in color. I placed odor eaters, damp eaters, lava rocks in the crawl to try to rid this smell. I wanted to ask if you came to a solution to rid the urine smell in your home?
> I was thinking that if the insulation that covers the air ducts under the exterior foil covering gets damp or wet, might that smell of cat urine? BTW: my HVAC is a packaged unit that is outside.


 Hi Andy,

Sorry to hear you have that problem.

Is the smell apparent to you when you are in the crawl? Is it localized anywhere? Do you get the smell year round? Have you tried putting a dehumidifier in your crawl?

Our smell is definitely originating in the crawl, not inside the duct work or up in the house. It is 'activated' by high summer humidity and is only sucked into the HVAC system when the blower is at top speed.

There is no complete fix yet. The smell went mostly dormant sometime in the fall and didn't come back until two weeks ago when we got the really heavy summer humidity back. 

Several guys have said that damp insulation can smell like urine. But I don’t think that is happening in my case.

For more on my current situation and thinking see *Current Details*, below.


*Things that have helped:*

Low relative humidity. Winter, late fall and early spring do this for us naturally. A dehumidifier and a sealed crawl would probably do it for us in the summer.

When the blower is in circulation mode, and the heat pump is off, the blower runs with less force, so there is less suction – and very little, if any, smell gets sucked into the HVAC system. 

Pulling air out from under the house, in that corner. I used a box fan. There is probably a picture of that earlier in this thread.

Hanging 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 some of the smell before it can get into the HVAC system.

(http://www.cleartheair.com/english/products/10/odor_eliminator_bag/13.html)


*Things that didn’t help:*

The UV light and UV protection glasses didn’t turn up any obvious, localized urine or dead animal residue. They do show an almost uniform scattering of faint, small spots on the upper side of the duct work – everywhere, not just in that corner. It shows rather strong glowing residue on the tin termite shield – but more on the underside than on top, and just as much far from the corner as nearby. Both of these phenomena seem more like the work of insects and/or material properties.

The odor eliminator chemical sprays were probably worse than useless. The first one changed the odor from urine smell to something else that was worse – and seemed to make things stink that hadn’t before, like the insulation between the joists. The subsequent sprays did nothing.

Keep us posted on your efforts and results. Good luck.

John


*Current Details:*

Once again, this summer, the smell is localized to the same 10x10 corner near the crawl door. 

One change from late last summer is that it is a URINE smell again and not the other smell. So the cause must be one of these:


fresh urine
the urine killing, spay-on chemicals don't work
something else is causing the smell
 
*Fresh urine?*

Last fall, I used spray foam and otherwise blocked every conceivable entryway. Only things smaller than a gnat can get into the crawl now. I have also been careful not to leave the door open while I am working under the house. So I don't believe this is a new load of urine.


*Something else? *

The smell is definitely ‘activated’ by high relative humidity. There are open, screen covered foundation vents in that end of the crawl so humid air is free to move into the crawl. 

I don't think the humidity is causing the insulation in that corner to get damp enough to smell. There are no puddles or sweating ducts in that corner - never have been. There isn't any insulation between the floor joists in that corner since I never replaced the stuff I pulled out last summer.

Several guys have said that damp insulation can smell like urine. But I don’t think that is happening in this case. Even in the parts of the crawl where we had sweating ducts and actual rainfall last year, there was never a urine smell. And those areas have all the same types of ducts, plastic ground cover and between-joist insulation that is/was in our smelly little 10x10 corner. 

Also, nothing about the materials, ducting or structure of that corner, or the environment outside, changed from the previous summer (two years ago). So it’s not very likely that the crawl suddenly started smelling all by itself. 


*The spray-on chemicals don't work?*

This seems most likely. The urine smell started 'suddenly, last summer'. (I think there is a book or movie with that title, but probably isn't a horror story about killer urine smells.)

I think that urine smell was ‘put there’ two winters ago and it was ‘activated’ when the summer humidity arrived. It's remotely possible that a neighborhood cat snuck in and peed while I was under the house doing some work, with the door open. 

But, since I found evidence of lots of rodent activity during last summer's 'battle' with the smell - I conclude that THEY did it. I think rodents peed all over the place in that corner two winters ago. Their pee must be very potent, long lasting and is activated by high humidity.

However, I don’t understand why it doesn’t show up under UV light. 

Maybe there is some other cause. 

In any case, I’ve wasted enough time on this thing. I’m not going to try any more direct smell removal stuff besides the Odor Remover bags. With them, it only smells moderately bad in late afternoon and early evening, in the summer, when the heat and humidity are highest.

I am going to try closing the vents and running a dehumidifier in that corner. Its an expensive, noisy fix - but one that will be good for the entire crawl/house, not just that corner.


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## Andy_39

I appreciate the info John! The same here the smell is activated with high humidity, I am in the northeast so right now is 70-80% humidity. In winter it goes away.
I've stuffed insulation in the foundation vents so humid air doesn't come in, I think one of the best things I did, before everything got sweaty.
I left one vent half open for some air circulation and in one vent I installed a foundation vent fan. Its a small fan maybe 6-8" diameter but it fits into the foundation vent opening and has a regular 3 prong plug. You can search on Internet for foundation vent fan, I bought it a while ago so I don't remember the website. It pulls some of the air from crawl to outside. I threw odor eater lava rocks, damp eater things none of those seem to work. My crawl is sealed only entry is thru the floor so no animals can get in/out. Chat soon,
Andy


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## Wildie

Andy_39 said:


> I appreciate the info John! The same here the smell is activated with high humidity, I am in the northeast so right now is 70-80% humidity. In winter it goes away.
> I've stuffed insulation in the foundation vents so humid air doesn't come in, I think one of the best things I did, before everything got sweaty.
> I left one vent half open for some air circulation and in one vent I installed a foundation vent fan. Its a small fan maybe 6-8" diameter but it fits into the foundation vent opening and has a regular 3 prong plug. You can search on Internet for foundation vent fan, I bought it a while ago so I don't remember the website. It pulls some of the air from crawl to outside. I threw odor eater lava rocks, damp eater things none of those seem to work. My crawl is sealed only entry is thru the floor so no animals can get in/out. Chat soon,
> Andy


 You should seal the crawlspace up as tight as possible, summer and winter. Humid air must be prevented from crawl spaces in our northern climes. 
When humid air cools in the crawl space, it gives up its moisture and it condenses on cool surfaces. This moisture feeds the growth of mold.
If necessary, seal it up and heat it with an electric heater, so that there are no cool surfaces that moist air can condense on.


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## John_W

Andy_39 said:


> I appreciate the info John! The same here the smell is activated with high humidity, I am in the northeast so right now is 70-80% humidity. In winter it goes away.
> I've stuffed insulation in the foundation vents so humid air doesn't come in, I think one of the best things I did, before everything got sweaty.
> I left one vent half open for some air circulation and in one vent I installed a foundation vent fan. Its a small fan maybe 6-8" diameter but it fits into the foundation vent opening and has a regular 3 prong plug. You can search on Internet for foundation vent fan, I bought it a while ago so I don't remember the website. It pulls some of the air from crawl to outside. I threw odor eater lava rocks, damp eater things none of those seem to work. My crawl is sealed only entry is thru the floor so no animals can get in/out. Chat soon,
> Andy


Wildie is right. To deal with humidity, you need to completely seal all your vents with moisture barrier material. Then, I've been told, you need to add a dehumidifier to further reduce the humidity - and warm the crawl.

If you have any gas or oil burning appliances in your crawl, make sure you have provided them with proper air intake and exhaust before you seal everything up.

On the other hand, if the smell is your only problem, and that vent fan helps, maybe that's all you need during the summer months. 

I only need to seal and dehumidify during the humid hot months. I'm probably going to come up with a way to easily seal and unseal my vents. Then, I just need to run the dehumidifier for a few months each year. I need the vents open in colder times so the gas furnace has a supply of combustion air.


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## jamesthoms

*Crawl Space Vapor Barrier*

I'm having essentially the same issue you had described.
I recently installed the cleanspace environment in my crawl space while we had our floors open and we had access.
About 3 weeks after the floors were closed we began getting a noxious smell through the basement and it started travelling up the pipes to other floors.
I can't figure out what it is. I read somewhere else that it might have been either the material the cleanspace is made of or the caulking used to fasten it to the walls of the crawlspace. What were you using to fasten your vapor barrier with?


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## John_W

jamesthoms said:


> I'm having essentially the same issue you had described.
> I recently installed the cleanspace environment in my crawl space while we had our floors open and we had access.
> About 3 weeks after the floors were closed we began getting a noxious smell through the basement and it started travelling up the pipes to other floors.
> I can't figure out what it is. I read somewhere else that it might have been either the material the cleanspace is made of or the caulking used to fasten it to the walls of the crawlspace. What were you using to fasten your vapor barrier with?


The 6 mil Dura-Skrim reinforced polyethylene membrane was fastened to the crawl space walls mechanically, with retarder buttons at 3 foot intervals and sealed all along the wall with Nuflex 110 Butyl Rubber Caulk and Gutter Seal. 

The contractor had to wear a very heavy duty air filter mask because of the dangerous fumes from the Nuflex. We didn't notice the smell up in the house and it dissipated fairly quickly down in the crawl.


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## jaydb2783

*Ozone generator to get rid of smell*

Hey John,

You'll find that you can use a ton of products and sprays to try to get rid of the smell, but they wont actually get rid of them-they only mask them, or cover them up, only to return later on. 

If you are serious about getting rid of the odors, we use ozone generators (we are a rental business) and we rent these things out to contractors, car dealers, hotels..tons of different places because they are awesome and work. Ozone is a gas, so you shouldn't be in the same room while it's running, but if you turn one of these units on (depending on how bad the odor is), it'll take care of your problem, just as long as you figured out the source of your odor first. 

We've purchased a few ozone generator units from a company called RainbowAir, I think they go by the Ozone Experts now. But here's the website http://www.ozoneexperts.com/

Hope this helps!:no:


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## John_W

jaydb2783 said:


> Hey John,
> 
> You'll find that you can use a ton of products and sprays to try to get rid of the smell, but they wont actually get rid of them-they only mask them, or cover them up, only to return later on.
> 
> If you are serious about getting rid of the odors, we use ozone generators (we are a rental business) and we rent these things out to contractors, car dealers, hotels..tons of different places because they are awesome and work. Ozone is a gas, so you shouldn't be in the same room while it's running, but if you turn one of these units on (depending on how bad the odor is), it'll take care of your problem, just as long as you figured out the source of your odor first.
> 
> We've purchased a few ozone generator units from a company called RainbowAir, I think they go by the Ozone Experts now. But here's the website http://www.ozoneexperts.com/
> 
> Hope this helps!:no:


Thanks for the suggestion.

I've considered ozone, but read that it can have unintended, bad side effects like damaging nearby electrical equipment. 

My HVAC gas furnace, indoor coil, blower and filter package, not to mention numerous power, cable, light and phone wires/outlets/boxes are all in or right next to the area that has that smell.


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## KG9

Question: Have you or anyone uphill from you, used copper-sulfate to kill roots in or on your/their property or downspout drains?

We did and this symptom immedeatly showed itself.


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## John_W

KG9 said:


> Question: Have you or anyone uphill from you, used copper-sulfate to kill roots in or on your/their property or downspout drains?
> 
> We did and this symptom immedeatly showed itself.


We haven't and I don't think anyone above us could affect that part of the crawl because of a berm on the uphill side of our property.


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## Vhegs

We are having a similar odor problem in a newly constructed home with a conditioned crawl. Any advice?


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## orange

Where are you located? Is the crawl space sealed so as to prevent "chipmunks, mice...."?


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## Vhegs

We are located in the Richmond , VA area. Construction was completed in August. Mold was discovered and had to be treated 3 times. The conditioned crawlspace failed inspection three times and had to be redone 4 times. There is a strong musty smell that comes up through the vents into the house. There is a constant smell in the crawlspace, smells almost like cat urine. They used some kind of glue like substance to adhere the vinyl and this also has a strong odor. The smell is stongest on the side of the house where the ac handler is - which is directly under the master bedroom. Have been waking up with headaches for the past few weeks. We have had an exterminator here - no evidence of any kind of wildlife. Do not know what to do.


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## hslammer

*cat urine odor caused by off gassing dura-skrim*

I had this same problem when I had my crawl space sealed. I ended up installed some carbon filters, fans, and a dehumidifier to help mitigate the odor. It's still there when it's humid and the hvac doesn't run much but it's much less noticeable with all the things I've done to try to eliminate it.

I recently had some folks giving quotes for a geothermal hvac install and some of them also do enclosed crawl spaces. Right away without me having to mention it they said the cat urine odor was off gassing from the dura-skrim material used to seal the crawl. They said they had that issue with their installs and contacted the manufacturer, to no avail. They had to change to a different type of material to seal the crawl. They said they only saw the problem with the multilayer poly reinforced dura-skrim type material. My crawl is sealed with 16mil black/white dura-skrim.


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