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Old 05-28-2012, 06:22 AM   #1
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Crawl Space

I have a dirt floor crawl space that has insulated form sprayed walls and heavy plastic on the floor over the dirt all sealed. My question is we still have a musty smell throughout house and condensation on our windows during certain times.He have a brand new furnace and all new duct work as we had large addtion built and installed all new. The crawl space has heating ducts through out as well. We do not know how to stop this musty smell .Should we consider pouring a concrete pad on crawl space ? There is visable moisture under the plastic covering the dirt floor right now so it is apprently doing the job of containing moisture under plastic however can you just poor concrete over that or what is the correct way to do it thank you so much


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Old 05-28-2012, 07:01 AM   #2
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Crawl Space

Use a psychrometer to check the actual humidity level.

There may be moisture coming through the foundation wall. You can duct tape a piece of plastic to the inside of the foundation wall and see if it collects moisture.

Also look for indoor sources. Boiling and cooking a lot? Long showers? Make sure the exhaust fans are being used.

I would not pour a slab until you tackle the moisture issue.


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Old 05-28-2012, 07:14 AM   #3
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Crawl Space

Things I'd be checking are, working gutters with down spouts that drain away from the foundation (not with at the foot of it) grade runs water away from the foundation, no mulch pulled up againt the foundation, no flower beds that form ponds right againt the foundation.
If the grade under the house is lower then the grade outside it may need to be raised.

Post some pictures of the outside of the house.
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Old 05-28-2012, 02:20 PM   #4
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Crawl Space

Is the HVAC unit under there?

Is there a separate air supply to the unit?

Was the odor in the house before the new HVAC?

Before the walls were SPF?

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Old 05-28-2012, 09:57 PM   #5
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Crawl Space

The interior of the walls in the crawl space have spray foam? What part of the country are you in? Typically, a crawl space is vented. If it's not vented, it has to be conditioned. You said you have HVAC ducts in the crawl space, but do you have registers and a return? If not, then you should have some vents in your crawl space. You don't need many, given the polyethylene sheeting, but you should have some (no less than 1/1500th of the footprint). So, if the crawlspace is 1500 sq feet, you should have at least two 6"x12" vents to let your crawlspace breathe.
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