Crawl Space Conditioning

Wow...it's been a while since I last posted.  But, things have been slow...until recently when I discovered lots of moisure in my crawl space.  Some background:

In the hot and humid south, moisture control is important in the crawl space to insure you don't allow mold to grow or provide ideal conditions for insects which can damage the underfloor joists for the house.   Old technology to control moisture was to put plastic on the ground (aka a vapor barrier) which would stop water for coming out of the soil.  It would also include putting in vents to "ventilate" the crawl spaces thereby removing moisture.  However...recent studies (Example:  http://www.smartvent.net/docs/crawlspacestudy.pdf or http://www.rlcengineering.com/csfallacies.htm) have shown that while some moisture is from the earth...the majority of it generally comes from the humidity in the air.   Note that folks are making a living off of fixing crawl spaces...for example:  http://www.dryprosystems.com/crawl-space-repair/vapor-barrier.html

Well...so far this summer has seen some very hot and humid days.  In the past week temperatures have been in the lower-mid 90s with the humidity between 65 and 87%.  Well...when those hot temperatures and the high humidity, when the air enters the crawl space, it can reach the dew point and begin codensation.  That's what I found in my crawl space.  I had been monitoring my crawl space using a wireless weather station with the transmitter located in the crawl space.  I thought it was fantastic that my crawl space had 20% humidity until I started getting suspicous during the past couple weeks 80+% humidity days.  So I checked the meter and the humidstat was broken.  I bought another weather station (Walmart - $15) and saw the truth...my crawl space had humidities in the 70-80% range.  That's bad.  And when I checked out the crawl space for mold, I didn't see any (good...probably because last year I went around and used a moldicide when I found some during a energy audit).  But I did find condenation all over what was left of my old vapor barrier (which was in various pieces...torn a lot...barely covering the sand floor). 

I had gotten an estimate in the past to encapsulate the crawl space and wow was it expensive:  $2800 for a 20Mil liner plus dehumidifer.  And over $7,000 for the full encapsulation which includes spray foam insulation on the crawl space walls. 

Screw that...I'm doing it myself.  Here's the method I used:  http://www.dom.com/about/conservation/pdf/crawlspaces.pdf  (Unvented crawl space).  Note: my crawl space is about 1300 sf and varies from about 4.5-ft in height to about 3 in height.  Not too bad. Here's a very  old pic when we moved in that shows the hot water heater (which now has insulation on it and all the hot water pipes have insulation as well):

See how it looks like crap in there?

So, on Saturday @ 6am,  I began 15 hours of fun in the crawl space.  I pulled out the old liner and any other junk that was in there.  I closed off all the vents and sealed them up.  Then I began putting up a 6mil liner with construction adhesive and super-all-weather gorilla tape.  Why a 6Mil liner vs the 20Mil liner above?  Well...first...a 20mil liner is like a frickin' pool liner.  The stuff is tonka.  Well, 6mil is more than strong enough since I don't store anything in my crawl space so why do I need something super heavy duty?  Anyhow, after putting down the liner I then sealed up the attic door (built a frame and put on weatherstripping). 

Overall,  it turned out great (I'll post some pics later).  The crawl space does not smell moldy/musty anymore.  The dehumidifer did a great job lowering the humidity from 78% to 48%.  I got worried for a while because my power usage shot up (I think the unit uses around 700W? And yesterday I used 44 kWh..yikes!) and stayed up for about 2 days, but its now caught up and turned off with the humidity is holding steady.

Now I have to recovery from my sore back and legs from working down there for so long...