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jim007 08-11-2009 02:37 PM

Crawl Space Moisture

I'm having my crawl space concrete encapsulated with spray foam insulation on walls. In addition to this, we are installing a new Lennox furnace with a powerful built in HEPA filtration system and adding a new Zoeller sump pump with back up in sealed system. The crawl will be equal to conditioned living space.

There are small, scattered patches of black mold on some of the joists as a result of a defective sump pump not discharging from previous owner.

My question is, will any existing mold on the joists eventually die since there will no longer be moisture to feed on? Will the musty odor eventually go away after complete encapsulation?

Someone recommended cranking up the heat when I get new furnace with HEPA filtration because it will dry out basement and the filtration will capture almost all spores coming back through the return air.

I would greatly appreciate any advice please.

Thank You.

Thurman 08-11-2009 05:56 PM

From my education with environmental issues-IF you are going to use the heat to kill the mold spores, you will be encouraging them to multiply instead. Killing mold spores will be done with chemicals. Such a simple chemical spray as one part household Clorox to three parts water will kill most mold spores. As to whether your new HEPA filter will capture any mold spores-I would not disturb any of them myself, just spray all of the mold I can see and spray into little cracks and crevices they might be in. Good Luck, David

jim007 08-11-2009 08:38 PM

Thank you for your response.

Are you referring to the air currents from the supply vent disturbing spores or the heat? Mold can't grow in dry conditions so how would heat cause them to multiply?

I've been reading quite a bit lately that bleach does not kills mold. Supposedly it takes away the stain so you can't see it. I wish I knew for sure.

Red Squirrel 08-11-2009 08:55 PM

Mold is kinda like a plant so pretty sure javex and other chemicals can kill it. Also I use this stuff called Benifect which I've been told kills mold, and other stuff like that. It's used in homes that had sewer backup, and it's natural. You can actually drink it!

And it's a great idea to try to bring the crawlspace to a "livable state". I have a split level so half my basement is crawlspace and during my researches I have found that lot of people totally neglect them, which is a waste. If properly treated they make great storage space so you can have more living space. I would definably physically ensure the mold is gone, then spray with benefect or other substance of choice, to be on the safe side. A dehumidifier also helps, you'll be surprised how much water you can pickup in a small amount of time. Though if you have visible moisture there is a much bigger problem and it should be looked at from outside. May need to dig up the foundation, but if you don't have gutters, start with that as it will minimize the water that gets to your foundation. Hopefully there's no weeping tile issues as that is probably not a DIY fix though maybe with enough research it could be one.

Maintenance 6 08-12-2009 02:09 PM

Molds are fungi. They are neither plants nor animals and do not behave like either. Common household molds need three things to thrive. Temperatures in the range of 40-110 degrees, moisture of 60% or greater and an organic food source (wood). Take away any of the three and mold ceases to be active. It will go dormant and stay dormant until conditions are once again right. You will always have spores. You can never remove enough of them to be mold free. Fact of life. If mold grew there it was because the conditions above existed. Driving out the moisture removes one of the three essentials. The other two, temperature and food, are beyond your control. You will never generate enough heat to kill mold spores. To clean up the residual stain, use a 10% bleach solution and wipe them down. Bleach is cheap and readily available. It is also one of the things that will completely disolve molds and break them down to their component parts. Wipe everything up thoroughly and discard the cleaning materials. There is no need for any magic potions. If the black stains are a concern, paint them with a sealer like Kilz or Zinnser.

jim007 08-12-2009 02:45 PM

Thank you for your recommendations. Would you happen to know if dry ice blasting to get rid of any mold, stains, dirt on the sub floor and joists is a worthwhile investment? Any idea what is would cost to have a company do this in a 900 sq. ft. crawl that will have a cement floor?

Maintenance 6 08-13-2009 06:30 AM

Dry Ice blasting is an accepted method to remove mold from the surface of wood. Properly done, it is very effective. Improperly done, it will cause more harm than the mold. I cannot comment on pricing. It will vary depending on area and distance from you to a company that can provide the service. If you choose that route, check the credentials of the company you are working with. Mold remediation is widely UNregulated and there are more than a few companies out there that haven't a clue about mold or it's behavior. Plenty of lead and asbestos abatement companies have jumped on the mold bandwagon only because it's quick easy money, homeowners are clueless about mold and the remediation processes share some equipment and procedures with lead and asbestos. Be sure you are dealing with a company that has experience in blasting wooden surfaces. Deep stains will not come out with blasting and the area will still require sealing regardless of which removal method is used.

ZTucker 09-20-2010 11:47 PM

Dry ice blasting is a very good way to remove mold. Dry ice blasting is known for killing 99.9% of mold. One advantage to dry ice blasting is the ability to get in to corners. There are other advantages, you can read a decent article on

One main disadvantage is the price (as Maintenance 6 mentioned). One factor that many people do not take in to count is the cleanup time. With dry ice blasting, there is no secondary waste.. thus the cleanup is a lot less.

steveel 09-21-2010 06:53 PM

I assume you have already taken care of gutters, downspouts, grading, ice dams, flashing, caulking.... all the things that can let water into the space from outside the space. Now you're air sealing and insulating, so that's good. what about the floor of the crawlspace? Vapor barrier of some kind?

More on killing mold

At the risk of hijacking your discussion, I am confronting similar issues at my place. Maybe you'll benefit if I ask my questions now instead of a separate thread, so here goes:

The first floor of my house (1924) has floor boards nailed directly to joists, above an unvented uninsulated unfinished basement bath. The first thing I did was to disconnect the water supply to the bath. That still leaves the joists and bottom side of the floor boards which are fuzzy with the nasty mold buggers.

I plan to set up my shop vac outside the house, and fire up my air compressor, and then attach both the blasting nozzle and the vaccuum attachment to a homemade handle of some kind, to blast & suck at the same time, just with air. (I'll wear my full HEPA respirator) Then I'll mix up bleach and vinegar under the above link in a garden sprayer and spray it all down, and finally suck and blow it all again. Set fan & dehumidifier to dry it all out. When I am done, since I have taken away moisture the remaining mold spores in the wood should be dormant and the wood will be stained but at least the surface will no longer be fuzzy. I don't care about the stains, I only care about preventing the stuff from continuing to bother my airspace inside the house. We'll deal with air leaking from the ucky basement up thru the floor boards (no subfloor) by eventually insulating walls and floor and making that conditioned space down there.

What do you think folks? will that do the trick?

Good luck on your job, Jim!


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