I'm finishing my basement. I am wondering about the north wall which is a 2x6 stud wall (walkout basement). I removed the fiberglass insulation an put 2 layers of 3/4" rigid insulation (sealed edges with silicone)... each has a R4. I will then put the fiberglass back. I am wondering about putting the plastic vapor barrier back. I don't khow how permeable the rigid insulation is and I don't want to trap moisture in the wall. It was -10 below last night and I didn't have any condensation on the rigid insulation. ( I haven't put back the fiberglass yet).The rigid insulation sealed up all the leaking seams and eliminated all the drafts.
Foam board, especially the one in your pics, act as a vapor barrier. The only issue with it is when you cut it and install between joists or studs. Then it needs to be taped, caulked, or foamed. You said you caulked them so you have completed your air seal. Adding another vapor barrier will only cause moisture problems and wood rot. I have been insulating homes for over 30 years and have seen the entire sides of homes that have had to be tore out and rebuilt because of the second vapor barrier.
A polyethylene vapor barrier should never be placed on a wall. This will trap moisture, which will rot out the wood. Water from poor drainage, flashing issues, and other moisture areas should be your focus. It's more important for a wall to be able to dry itself than to trap water vapor with a plastic barrier.
It is a universal construction specification to have: the exterior walls above ground coated in water barrier Tyvek, concrete foundations beneath the ground coated in asphalt, major perimeter drainage around the footing of the home, then the siding, house wrap, sub wall or OSB, then the studs, THEN installing the bats or blown in insulation and THEN a vapor barrier on TOP of the bats. One needs ventilation designed into their foundation and walls. Lots of stuff actually allows some air flow but you have to understand when and where that works, what is allowed in the city or county buildings and code specifications.
For a basement one needs a proper perimeter or foundation drain, perforated pipe sitting just off the footing of the walls, not on the footing. Landscape fabric covering the entire perimeter drain pipe and then drain rock back fill. No water allowed to flow TOWARDS the home's foundation!
Ventilation between crawl space or basement is critical. Attic fans, exhaust fans pull the air through the walls to stop mold and fungus and dry rot. Fans are not necessary if one understands heat rises and cold air comes in at the bottom. Ventilation is oh so important!
Drainage, designed and executed properly for your foundation is the top most important thing you need to do. Otherwise, everything else is either assisting or being a band aid.
The picture shows you are ready to put up the bats of insulation or spray insulation then install plastic as a vapor barrier.
My first worry is your drainage outside of this basement. If there is any indication of moisture on those 2X6's or concrete floor, you have to take care of that problem first. Do you have a low spot in your basement floor that has a DRAIN?
Look at your perimeter of your home closely. ALL slopes have to slope AWAY from your foundation. Check to make sure that the contractor actually installed a proper foundation drainage system. Check to make sure that contractor applied asphalt on the foundation's concrete between the outside of the foundation and between any soil or rock.
Why did you remove the old insulation? Was it wet? Big red flag!
Note: I am very for ventilation! But the entire reason for vapor barriers is condensation. A plastic barrier will attract the condensation AWAY from your siding or interior wall board. Condensation will happen no matter what between two surfaces of different temperatures. A vapor barrier protects your wall board by collecting the condensation versus having the wall board collecting the condensation. The caulking was probably a no no for air flow.