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Musty odor in crawl space, reading a lot, getting confused

Musty odor in crawl space, reading a lot, getting confused

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  #1  
Old 08-01-13, 05:22 AM
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Musty odor in crawl space, reading a lot, getting confused

20+ year old house in Atlanta, Ga area
2'-3' crawl space
outside vents (9 or so around the house)
dirt floor
plastic on dirt floor from block wall out about 10', (not in middle of house)
all exposed dirt is dusty dry
block walls are dry
HVAC system under there

We have a musty odor in crawl space that penetrates into the home. It's been there a while but seems to be worse now. I know it's been a wet year here.

I know there's a white dry powdery substance on the floor joists that wipes off easily, with occasional areas of small dark dots of mold. (I will try to get pictures later). Seems to be mostly on the bottoms of the floor joists, but some have it on the sides as well.

There was some water seepage several years ago, but landscaping fixed that. All seems dry under there, even under the plastic.

I searched yesterday for answers and now I'm really confused!:

-- keep it vented or close up the vents?
-- spray with bleach or with vinegar? (I sprayed with vinegar yesterday as much as I could)
-- run plastic up walls to floor band to cover block or spray a sealer on block?

Will go under there today to see if the vinegar helped.

How do you get rid of the musty smell? OdorBan or similar product?

Looks to me like the dry powdery stuff may be dead mold left from years ago. If so, what's the best way to remove it, Shopvac?

Can I spray paint or stain on the floor joists to seal them? Will that kill any remaining mold?

The more I read the more confuseder I get! (It's a joke, teachers)
 
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  #2  
Old 08-01-13, 05:44 AM
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Vinegar and bleach are useless.
Need something like Bora Care or Timbor. Google it.
Check the humidity level.
Some forms of fungus eat the cellulose that holds the wood fibers together in those joist and subfloor. Left long enough and you can remove the joist with a 5 gal. bucket by hand.
 
  #3  
Old 08-01-13, 07:16 AM
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research seems to indicate powdery mildew and not mold.

Also, interestingly enough, looks like Antifreeze is a good fungicide. Borax will have to be dissolved before use.

Thinking of spraying with Antifreeze, now . . . . what do you think?

Once I kill what I can I will work on sealing and keeping it dry.
 
  #4  
Old 08-01-13, 09:11 AM
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OK, here are some pics I just took:



Hope you can see them, not the best quality.
 
  #5  
Old 08-02-13, 10:32 AM
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Crawlspaces should either be open to the outside and sealed from the house or vice versa.

Given that your HVAC is down there, I would opt for sealing from the outside and making this conditioned space but makeup air for combustion has to be taken into account.
 
  #6  
Old 08-03-13, 09:09 PM
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Where is your R-13-19 floor insulation, or supply duct insulation, per code? Chapter 11 - Energy Efficiency

Chapter 11 - Energy Efficiency

If closed crawl; http://www.buildingscience.com/docum...ance-and-codes

Mildew is a form of mold; Mold Resources | Mold | US Environmental Protection Agency

BSI-027: Material View of Mold — Building Science Information

The joists are a different temp than the floor/room above and collect condensation; BSI-009: New Light In Crawlspaces — Building Science Information

Gary
 
  #7  
Old 08-04-13, 03:31 AM
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I tend to agree with Gary in that there is no floor insulation to keep the humidity from the rooms above from migrating to the joist area. No logical reason for the entire crawlspace not to have plastic on it. Was that a money saving method of not putting it all over??

You are going to get information from both schools of thought on the crawlspace. Some will advocate sealing it completely up all the way to the sill plates, closing the vents and making the crawlspace a conditioned "room". I have seen rivers form under houses with such encapsulation, and in our climate, cross ventilation will take care of moving the stale air from the crawl. So hang in there for more confusing information. You'll have to decide ultimately. I believe, however floor insulation is an absolute MUST as well as completely covering the crawlspace with plastic.
 
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Old 08-04-13, 05:25 AM
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All ducts ARE insulated, the one you see that is not is the dryer vent to the outside.

I built the house in 1988 and at the time floor insulation was just a thought, not required. I thought about doing it but don't want to enclose any mold between the floor and the insulation that would make things worse.

Years ago the idea was to have plastic around the floor only out a few feet and to leave about 6" away from the wall to allow for evaporation of condensation. I thought 10' was good and eventually did cover all the way to the foundation. Only about a 10'x20' section in the middle is uncovered. It is dusty dry there.

I think the vinegar seemed to work. I noticed it would bead up on the wood and if I soaked it, most would drip to the floor. I added a few drops of dishwashing liquid to the second gallon to help break up the surface tension.

I think I will spray a second round of vinegar sometime this week. I also added a dehumidifier and a fan. I will remove the fan once it gets good and dry under there. I need to look for what the best level of humidity should be.

I may have to seal it but want to make sure any mildew/mold is gone. I also use the crawlspace for storage of tools, so it will never be completely sealed.
 
  #9  
Old 08-04-13, 09:58 AM
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Running a dehumidifier in a crawlspace that has vents open to the great outdoors is an exercise in futility AND a huge waste of electricity.
 
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Old 08-04-13, 01:59 PM
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The lack of a dehumidifier is not the problem, it's the moisture coming in from outside and up from the ground - you need to stop those.
 
  #11  
Old 08-05-13, 12:59 PM
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Had to run the dehumidifier for a while to dry it out some, and to dry up the vinegar.

I've closed all the vents as best they can be. I understand sealing everything up, but if I go in and out on a regular basis, what's the point? It will never be completely sealed.

From the links that Gary sent, looks like it's not from ground vapor but from condensation from the air. According to what I read looks to me like using rigid board on the floor joists and venting the crawl space is the answer.

I don't want to seal in any mold that is already there. And, I just don't know how that will work with all the HVAC ducts, plumbing and electrical down there. It doesn't look like I'll be able to seal up everything.
 
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Old 08-05-13, 01:32 PM
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Completely sealing a crawlspace is a task in itself. Theory wise you are encapsulating the entire crawlspace so no outside air can get to the area. This is done with heavy gauge plastic and foam boards and duct sealing material (not tape). The theory continues with opening your HVAC system to this area and making it a part of your houses' circulation.

In some areas of the country, it may be a helpful manner in keeping inherently moist air from settling in the crawl. As I stated in an earlier post, you have vents installed in the crawlspace. They were installed under possibly the Southern Building Code. Transformations in code (not always sane) are dictating different approached to this without consideration of what part of the country you live in.

Good luck with the sealing, and if it fails, open all your vents back up to allow your nice breezes evacuate the area like they were designed to do, and have been doing in our area for many years.
 
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Old 08-05-13, 02:32 PM
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If you go with a "encapsulation" method, it must be complete for it to be successful.

Even though the dirt in the center appears to be "dry" it may only seem that since any moisture from below evaporates into the crawl space. It may just be a wick that provides a sournce for moisture. - Cover the ENTIRE floor and tape the joints.

It is good you have poly running up the sides and I assume they are sealed well. The remaining portions of the block walls and and the vents must also be sealed/caulked.

Also, pay attention to any gaps in the framing.

If there is a need for any intake air for the HVAC, that could also be a source of external moisture.

Odors are very tough to eliminate because the nose is sensitive and often notice them because they are trying smell them unconsciously or consciously.

It will also take time to get the odors out of anything (porous or wood).

Dick
 
  #14  
Old 08-07-13, 08:04 PM
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I'm glad you are reading the links provided, from some answers given here. The diffusion will be very minimal from RH above, as you read. OSB/plywood is a very good air barrier, stopping any moisture (and collecting/distributing it) in the material- no diffusion through it until completely saturated; BSI-038: Mind the Gap, Eh! — Building Science Information

Your OSB decking is a Class 2 vapor retarder;BSD-106: Understanding Vapor Barriers — Building Science Information

The vapor drive from pressure/temperature is always from the crawl to rooms/attic, seldom the other direction with it air-sealed, use a complete ground vapor barrier; http://www.fpl.fs.fed.us/documnts/te...entilation.pdf

Condensation basics in the crawlspace; BSI-038: Mind the Gap, Eh! — Building Science Information

Closed crawl is suggested; Joe's Top Ten :: Joseph Lstiburek

FIGS. 7-9 and #12: RR-9302: Humidity Control in the Humid South — Building Science Information

Foamboard the rim joists; Info-401: Air Barriers

Air seal the crawl; http://www.wag-aic.org/1999/WAG_99_baker.pdf

And change out the dryer ducting for smooth wall ducting w. insulation/vapor barrier; outside the transition room area; http://www.hcpdc.com/pdf/Dryer%20Ven...quirements.pdf

Gary
 
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