After 6mil vapor barrier in crawl space, moister gathering between insulation and flooring

Question

Living in the Charlotte, NC area, and have had problems with moisture under the house.

Last year, I lined the floor of the crawl space (ranges from 4.5' to 2' high) with 6mil plastic. I'd say 90% of the area is covered, with some edges near some of the concrete walls exposed. Plastic is secured with metal clips shoved into the ground, and it is overlapped but not taped (the moisture problem wasn't bad, so I was primarily concerned with covering the majority of the ground).

NOTE: The crawl space ranges under a front/back porch, so the inner center of the ceiling joists are insulated, and the joists under the porches are exposed (and sometimes receive moisture from driving rain).

This year, our hardwood flooring has started to cup in some areas, and we also saw one section of linoleum in the laundry room bulge. Upon inspecting the crawlspace, I found the following:

• Insulation installed 10+ years ago was installed with the paper side facing the flooring
• In pulling down the insulation under the affected areas, I've found moisture gathering between the insulation and the floor (so between the paper side and subfloor)
• There is a great deal of condensation on the outside of the primary feed from the air conditioner (the 2' duct work feeding the whole house). During the heat of the summer (about 2w ago), the condensation was sufficient to cause standing water on the plastic underneath the vent (though that water has now evaporated). This dampness started about 10' from the A/C (where the primary feed duct splits to feed the rest of the house)

I think I should I replace the existing insulation with faceless insulation, but I'm looking for advice.

I'm also curious if installing the vapor barrier on the ground might be causing increased moisture potentially gathering between the floor and the insulation.

Answer 1

It's best to not use faced insulation here for the reasons you've noted, But new insulation may not be necessary- you can carefully peel the face paper off and re-use what you have as long as it's not moisture-laden itself. Also, the ground sheet poly isn't exactly a waterproofing. It's purpose is to reduce, not eliminate, the moisture evaporating from the soil so normally having a foot of overlap between sheets is fine without taping. You should also have good crawlspace ventilation to go with this.

Phil