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tim5055

Crawl Space Encapsulation

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. . . but what RH should I be shooting for in the crawl? Once it gets there I can dial back the dehumidifier as the dial on it just says dryer with an arrow to the right.

I'd expect the crawlspace to have roughly the same relative humidity as the inside of the house, perhaps a bit higher. Understand that relative humidity is a moving target - it's dependent on temperature. So unless it's the same temperature in the crawlspace as in the house, you'll need a psychrometric chart to do the conversion.

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I think you might want to dial back the humidifier. At 40% you might end up with interior humidity traveling to the crawl. I think you want to be somewhere near 50/50 with just a tad toward the dry side in an older crawl.

Personal opinion based on not a whit of science. Just seems to work for me in my locale. If I were practicing in S.C. or Texas or California, I'd probably revise my opinion after I'd been living there long enough to figure out what I think is working.

ONE TEAM - ONE FIGHT!!!

Mike

Thanks!! Right now the sensor is just sitting on a shelf by the door to the crawl. Prior to encapsulation there was no mold in this area, so I assume my crawl has several micro-climates. I'm moving the sensor to the area that had black mold under the insulation and on the joists and see how the readings change.

Well,

You've got me gnashing my teeth at the term "black mold." You don't have "black mold" you have common mold that's ubiquitous in the environment - and probably a few hundred varieties of it. All you are doing by controlling the humidity is getting to the point where there isn't sufficient moisture to allow the mold that is there, which has always been there and will always be there no matter what you do, to reproduce faster than it dies off.

Once you are there, you'll assume there isn't any mold and you'd be wrong 'cuz it will always be there regardless of what you do. It on your clothes, it's in your nose, it's stuck to your eyes, it's in your lungs and stomach and your internal organs. Hell, it's on the food in your fridge and you probably pissed out a few billion spores this morning when you woke up. If you've got a kid or new grandchild that kid is slathered in the stuff and is breathing it this very second.

Stop fretting about stuff that you can't control that doesn't need fretting about.

ONE TEAM - ONE FIGHT!!!

Mike

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No worries Mike, I'm not a mold nut. Probably a poor choice of descriptive words in my haste. This one area of the crawl has a greater population of growing stuff that is black in color. I'm not trying to say it is a specific mold.

As I suspected this area has a higher RH, as it started climbing when I moved the sensor there. Maybe a fan is in order to keep the air moving.

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No worries Mike, I'm not a mold nut. Probably a poor choice of descriptive words in my haste. This one area of the crawl has a greater population of growing stuff that is black in color. I'm not trying to say it is a specific mold.

As I suspected this area has a higher RH, as it started climbing when I moved the sensor there. Maybe a fan is in order to keep the air moving.

You've abundant dehumidification power in your AC. If the humidity gets too high in your crawl, try ducting a little air from your AC into it. Use 'trial and error' to arrive at an acceptable level of RH. I agree with others on 40 to 60% levels.

Any mold growth that's big enough to see should be removed. Use Tilex.

Marc

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I think you might want to dial back the humidifier. At 40% you might end up with interior humidity traveling to the crawl. I think you want to be somewhere near 50/50 with just a tad toward the dry side in an older crawl.

Personal opinion based on not a whit of science. Just seems to work for me in my locale. If I were practicing in S.C. or Texas or California, I'd probably revise my opinion after I'd been living there long enough to figure out what I think is working.

ONE TEAM - ONE FIGHT!!!

Mike

I agree with hausdok on this. That dehumidifier will suck to water out the "P" traps if it were in a house. It has no problem eliminating the humidity in the crawlspace. I'd keep it around 60% as do most people in my neck of the woods. 40% is too low.

The wood moisture content should stay under 19%, which Clemson states is the key number to stay under. (Not a fan of by the way. GO GAMECOCKS!)

You're overthinking it a little. You spent your money wisely. Don't worry about it. This system actually works.

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Thanks to everyone for taking the time to read and respond.

After moving the sensor to what I suspected was the "wetter" area the RH has risen to 59%. As I suspected I may need to move the air around a little.

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Well, a new chapter in the crawl encapsulation. We developed a smell, concentrated around the kitchen cabinets that is best described as that of cat urine. As we do have cats I broke out the black light looking for signs of urine in areas that we were noticing the smell with negative results.

So, I remembered - Google is your friend. A search has revealed that this is reported by some folks who have their crawl space encapsulated. No consensus, but off gassing of the plastic used or changes (rise) in the humidity below the plastic are the direction most fingers are pointed. I don't raelly notice the smell in the crawl, but the wife says she does.

Inspection under the house revealed a large hole in the sub floor (hidden by insulation) that the original carpenter cut to route the cooktop downdraft pipe.

The "cure" that is talked about is installing a vent system under the plastic, similar to a Radon remideation system. The main difference is that this only need to vent out of the crawl, not above the roof. I'm figuring I can do this myself for less than $500 so I guess I have a New Years project.

Any suggestions on how to label it so a future inspector does not flag it as an improperly installed Radon system?

Thanks

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Well, a new chapter in the crawl encapsulation. We developed a smell, concentrated around the kitchen cabinets that is best described as that of cat urine. As we do have cats I broke out the black light looking for signs of urine in areas that we were noticing the smell with negative results.

So, I remembered - Google is your friend. A search has revealed that this is reported by some folks who have their crawl space encapsulated. No consensus, but off gassing of the plastic used or changes (rise) in the humidity below the plastic are the direction most fingers are pointed. I don't raelly notice the smell in the crawl, but the wife says she does.

Inspection under the house revealed a large hole in the sub floor (hidden by insulation) that the original carpenter cut to route the cooktop downdraft pipe.

The "cure" that is talked about is installing a vent system under the plastic, similar to a Radon remideation system. The main difference is that this only need to vent out of the crawl, not above the roof. I'm figuring I can do this myself for less than $500 so I guess I have a New Years project.

Any suggestions on how to label it so a future inspector does not flag it as an improperly installed Radon system?

Thanks

Cat oder eliminator. Wouldn't it be easier to just cap the hole with plywood and seal it with a band of liquid nails?

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Cat oder eliminator. Wouldn't it be easier to just cap the hole with plywood and seal it with a band of liquid nails?

Thanks - I thought about that, but wile the smell is strongest in this area we do smell it in other areas. I'm guessing any penetration of the floor is allowing it to enter the house.

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Beginning Christmas with a discussion of cat urine odor......

Label it DeStinkerAtor, and have a label of a cat pissing with the red circle and slash (the universal "no" sign).

Better yet, ask Katen what to do.....(with the cats)....

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What if a small duct from the central heat/cool system were to serve the crawl, and across the crawl space install a small exhaust vent (under the kitchen perhaps)? The duct supplies positive pressure which is relieved by the exhaust opening. The odors go outside and it'll also help hold down the RH. Openings in the building envelope at the floor level will have to be closed or sealed.

Marc

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. . . Better yet, ask Katen what to do.....(with the cats)....

Have you tried curiosity?

Well, the best I can tell it's really not a cat issue - it's something that periodically happens after encapsulation.

But as the cats belong to the wife and her job requires an above average level of competence with devices that can cause bodily injury I'm not going to go there[^]

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What did they encapsulate with?

Black polypropylene? Some of those products are covered with a layer of release oil so that they won't stick together. I find it pooling on wrinkles in the barrier sometimes. Maybe that stuff sticks - I don't know, I'm always wearing a mask. Maybe the barrier needs to be washed down with soap and water.

ONE TEAM - ONE FIGHT!!!

Mike

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I see I never reported back on the odor issue. I talked with the owner of the encapsulation company and he said about 10% of the crawls he does report odor issues after the fact. He had his guys come out and install a small radon fan under the plastic in a depression they dug under the encapsulation material in the middle of the floor. This was vented outside the crawl. Well, about two days after the install the odor was completely gone.

As to the humidity I dialed the dehumidifier back and the RH now runs 50 - 52% all the time.

All the AC ducts are run int h crawl and the leakage from them keeps the crawl conditioned at about the same temperature as the house.

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Sounds great; problem solved. Time to move again.....

Well, I'm retired. As soon as the wife decides she has had enough of work this house will be on the market....

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Gotta love the ability to search and refresh your memory from the older posts when you need it.

This helped me a bit tonight!

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