Fiberglass insulation in a crawl space tends to soak up moisture and humidity, goring mold and eventually causing it to "drip" off the ceiling. And even when it's where it belongs, wet fiberglass is a poor insulator. TerraBlock is a unique, durable crawl space insulation and liner in one. It's the first insulation product created specifically for rough, uneven crawl space floors, which can be as cold as 55°F. Made for floors and walls alike, this provides a puncture-resistant, padded solution for your crawl space.