According to mold expert and author Jeffrey C. May, fiberglass insulation should never be used below grade. Here’s why:
“The material collects biodegradable dust, starting from the day it is installed,” he writes. This dust can become nutrients for some species of mold if basement isn’t equipped with the proper dehumidifier.
Moreover, dust and other potential nutrients for mold start collecting in below-grade fiberglass during construction, and not many builders or remodelers dehumidify during construction.
Read the full report at May Indoor Air.