Why there’s moisture in my basement?
Sub-grade basements present specific challenges for insulation in that concrete walls are full of moisture. If not accounted for or insulated correctly, your basement will quickly become a breeding ground for mold and mildew. So the challenge is what to do with all that moisture. Studs, drywall, floor joists and even fiberglass are all susceptible to mold. If you ever have a scenario where moisture is trapped against one of these materials, it’s only a question of when the mold will take root. It’s all too common to see framed walls adjacent to concrete with a vapor barrier between the studs and drywall. The cavities are filled with fiberglass, which eventually becomes saturated as the concrete releases water vapor. The problem with that setup is the location of the vapor barrier. The right way to insulate that basement would be to install a vapor barrier like rigid foam board next to the concrete wall to lock out moisture, and then insulate with fiberglass batts. Just make sure the barrier is complete from top to bottom and the joints are sealed appropriately. Closed cell foam is another option to consider. It’s sprayed in place and forms tiny, waterproof cavities that do not permit airflow. With about 3″ of closed cell, you achieve between 0.1 – 1 perms resulting in an effective building envelope and vapor barrier (harsher climates require 4+ inches). Closed cell foam is very dense and offers approximately R-7 per inch, not to mention the structural and sound deadening benefits. Foam also seals even the tiniest gaps and is highly mold resistant. Closed cell foam is a top choice for insulating your basement. It is more expensive, but you often get what you pay for. DIY kits are available and suitable for small applications. You should not consider open cell foam as it does not have any vapor barrier properties and will also absorb moisture, promoting mold growth.