I am staring down the barrel of a new project that is going to slow all other projects down for a short {I hope} period of time. I need to seal up and dehumidify my dirt floor crawlspace.
The wife and I built a single family house in 2002. It's about 1500 sf heated area and a porch that wraps around 3 sides of the house, all within the exterior perimeter of the dwelling. When we built it, we did what was the norm in the area and put it over a crawl space. We covered the ground under the heated part of the house with black plastic sheeting and ignored the part under porch.
We've been struggling with high humidity under there ever since. All we've done {that we thought was} constructive was install a squirrel-cage fan on a timer to circulate air under the house, exhausting it out a foundation vent. Relative humidity is still a problem at over 80% most of the time, complete with some mold on the floor joists.
I wanted to farm this work out so I could continue with the two other projects I'm working on, but more than $5500 to encapsulate under just the heated part of the house was considerably more than I am willing to pay.
So....
I have this plan that I'm currently going forward with. I've ordered some 12 mil three ply vapor barrier plastic(?) sheeting and the corresponding roll of seam tape and I'm going to put it under the porch area, including going up the inner and outer foundation walls about two feet. I will try and fasten it to the foundation walls with a polyurethane adhesive that comes in a caulk gun type cartridge. I expect that to marginally improve the situation. When that is complete, I will order more of the vapor barrier material to do under the heated part of the house while I address the mold problem.
I'd love to hear from anyone who's tackled this issue already and may have some helpful hints.
Thanks,
Mark