Basement Insulation Between Living Space and Crawl Space

I have a ranch hone with a finished walk out basement that occupies about half of the home's sqr ft. The other half is just a sloped crawlspace with plastic covering the dirt. The wall that separates the basement from the crawlspace is comprised of a half cinder block (lower) and studs (upper half) for an almost 50/50 split the entire length.

I have a musty smell in the basement and noticed some green mold starting to take form on the studs of the shared wall with the crawlspace. The wall is finished with the following layers: Drywall -> Kraft Face -> Batting -> 2x2 furring strips -> cinderblock. I have HVAC in the basement as well as a portable dehumidifier which I have to empty every day and just barely keeps 55% RH.

There is an obvious lack of a vapor barrier and was wondering the best way to control this without having to rip down 60 ft of drywall. Initial thoughts were to:

A) cover the wood framing from the crawlspace side, however am worried about trapping moisture in the wall cavity evaporating from the cinderblock / sill below.
B) Create a negative airpressure in the basement to reduce humidity by power venting from a floor return to the outside.

Any thoughts/ideas would be greatly appreciated!

 

I would look outside first. Try to determine why moisture is entering the area. Look at gutters, downspouts, pitch & cracks, in the foundation.

 

There isnt any obvious signs of moisture and have a gutter system and downspouts tunneled away from the house. In the rooms where the cinderblocks are exposed there isnt any sign of water seeping through the blocks. Im guessing the moisture is coming from the air. I live in Charlotte, NC where the outside RH is always near 80% sprint / summer / fall and the crawlspace is vented.

The Cinderblocks have tar / foam on the exterior side as well.

 

Unfortunately, my experience is with the exterior. The most I've done with the inside is use dry-lock on the walls. Maybe that along with a dehumidifier would be enough. Wait for some other responses.

 

What is going on with the crawl space? Is it also provided with HVAC, and if not what level of outside air venting was provided? The poly over the dirt is not enough to avoid moisture build up if it is built as an outside space. It requires air movement through venting.

 

The crawlspace has the small grate vents located around the perimeter and the air space is not conditioned. The humidity here can just be brutal during the late summer months and this year was no exception.

I think the humidity is condensing near the drywall / studs in the upper half of the wall on the crawlspace side and doubt there is any abnormal cinderblock foundation water penetration. In the drywall-less basement room I see no signs of efflorescence, cracks, or staining of any kind on the cinder block or floor edge.

Im thinking I should cover all exposed framing / insulation in 4-6mil plastic from the crawlspace side and attach a powered air duct to the plastic near the center of the wall. I hope this would; A. Keep crawlspace moist air way from wall stucture and B) draw out any moist air from the basement and cinderblock cavity and push it via a pipe though the crawlspace and outside of the foundation.

Does anyone see any obvious problems with this or think it wouldnt help?