Crawl Space Insulation Problems

Crawl space insulation will provide a more comfortable living space, but it can also present problems for the homeowner. High humidity levels, direct exposure to water, rodents and incorrect installation can all lead to a degradation in the insulation and the protection it provides.

Crawl space insulation problems can increase home energy costs.

An investigation of potential problems can help homeowners with proper installation and ongoing maintenance.


Moisture is the enemy of insulation and can lead to problems like mold, mildew and erosion of the product. Moisture can be caused by high humidity levels in the crawl space or direct exposure to water. Direct contact with water can occur when open crawl spaces expose insulation to blowing rain or flooding. Enclosing the crawl space, applying a water protective barrier, installing a flood pump or proper ventilation can help reduce crawl space moisture problems.

Installation Problems

Problems with crawl space insulation can start with incorrect installation methods or utilizing the wrong type of insulation. For vented crawl spaces, insulation should be installed on perimeter walls, between the floor joists and around water pipes and air vents. Insulation for an unvented crawl space should be applied to the perimeter walls. Standard fiberglass insulation with backing can retain moisture and is susceptible to mold and mildew problems, making it unsuitable for crawl space projects. Blanket or spray foam insulation with a moisture barrier element will solve this problem.


Crawl space insulation is generally left uncovered and exposed to pests of all types. Fiberglass or other fibrous types of insulation can be used by rodents as a nest or as food. Dried rodent urine or feces in insulation can present a health hazard to humans. Insects such as carpenter ants and termites tunnel into spray foam insulation as a home or to gain access to living spaces. Insulation products with an insect repellent work best for crawl space installations.

Wear and Tear

Wear and tear on crawl space insulation can break down the product or render it ineffective. This can occur when insulation is removed or altered to provide access for projects such as plumbing work, electrical installations, cable TV wiring or floor repair. Gravity can also cause insulation to sag or fall from floor joists. These problems can leave areas exposed to the elements.