What is a common issue with insulation in unventilated crawl spaces?

In unventilated crawl spaces, a common issue is mold growth, which can flourish due to damp conditions often associated with these spaces. When insulation is installed in an unventilated area, moisture can become trapped, creating an environment conducive to mold. This occurs when humidity levels rise and there isn't adequate airflow to remove moisture. Mold can compromise both the insulation's effectiveness and the structural integrity of the building, as well as lead to health issues for occupants.

The choice of improper type of insulation or damaged insulation can be relevant in specific contexts, but they are not as widespread or significant as the mold growth issue directly resulting from moisture accumulation in unventilated conditions. Insufficient insulation material can lead to problems like thermal inefficiency, but it does not directly correlate with the specific challenges posed by the unventilated environment and its impact on mold development.