I have a 14 foot basement which is waterproofed. It has a french drain and a heavy duty white plastic covering the entire outside wall. I have half of the basement finished. My question is how do I insulate the side of the basement wall that is concrete? Is it okay to fill the cavities with insulation since the plastic is already there? The plastic is not necessarily a vapor barrier but a way to direct any leaks down to the french drain.
Don't fully understand but I see no reason not to install insulation on top of vapor barrier.
If the plastic is only there to direct water down, it is not necessarily thick or durable enough to be a reliable vapor barrier. I'd recommend adding another vapor barrier just to be safe, because better safe than sorry. Alternatively use a mold-proof insulation, such as mineral wool.