There are two types of insulation materials you can choose from: absorbent insulation and reflective insulation. Absorbent insulation, particularly fiberglass, is the most used insulation material in the industry. Absorbent insulation is great at absorbing heat, but it is also great at absorbing moisture. It can host mold and fungi, so try to keep that in mind when choosing an insulation type. Unless you want to replace your insulation every few years, you need to choose something a little more durable. Reflective insulation types are the best for crawl spaces. Reflective insulation controls airflow and retains heat in a space by reflecting it. These panels not only make sure your foundation is warm, but it also does so without contributing to mold growth and lasts for years.