Whether or not you need a vapor retarder hinges on three main factors your climate your home and the location of the wall you re insulating.
Vapor barrier basement wall framing.
Fiberglass insulation inside a bag hanging from the rim joist down along the foundation wall.
In short basement wall systems should never have any polyethylene vapor barriers.
To know if you need a vapor retarder ask yourself a few basic questions.
Not to be confused with a vapor barrier which is placed on the warm side of the wall just in front of the insulation and behind the drywall a moisture barrier goes against the basement wall and.
A vapor barrier is also helpful to keeping a basement insulated and warm.
Building codes usually require a vapor barrier 4 mil plastic sheeting on exterior basement walls if the framing is attached to masonry or concrete surfaces or if the wood framing butts up against the outer basement walls.
When the mold grows it will spread to everything around it studs drywall etc.
Experts suggest that installing these within basement walls leads to moldy basement insulation.
With fiber insulation and a vapor barrier moisture can get trapped in the insulation leading to moldy insulation and decay in the wood framing.
Polyurethane sheeting is a typical vapor barrier that contractors use to prevent moisture from penetrating the walls of a basement.
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So there is enough gap for air to flow.
Plastic vapor barrier against concrete wall fiberglass insulation inside stud wall then drywall.
If you have a framed wall that is adjacent to a concrete foundation wall where the vapor barrier is next to the drywall in front of the studs the fiberglass insulation gets wet and becomes a breeding ground for mold.
That is if the studs are going to touch the concrete wall.
Dedicated vapor barriers are typically installed on the warm side of walls behind the drywall and right in front of the insulation.
Of foam against the wall this should not be a problem in your climate.
The material is stapled to the frame of a basement wall before it is finished with plaster or drywall.
Most jurisdictions require a 4 mil plastic sheet vapor barrier for basement walls against concrete.
Stud wall filled with fiberglass insulation an inch or two away from the concrete wall.