Crawl space insulation usually stops working for one of four reasons: it's wet, it's moldy, it's contaminated by pests, or the home's ventilation setup is working against it. Wet, moldy or pest-soiled insulation needs to come out. If it's in good shape but your home still isn't efficient, sealing and insulating the foundation walls instead may be the better fix.
We hear this question most from homeowners who've been in their house ten years or more and have started to notice:
- Energy bills creeping up
- Floors that feel colder in winter than they used to
- A musty or damp smell in parts of the house that wasn't there before
Here are the signs that your insulation may no longer be doing its job.
1. Wet insulation
If the insulation under your home looks stringy or is hanging down, it may be wet or saturated.
Most crawl spaces have vents around the foundation meant to let air flow under the house and keep it dry. But South Carolina summers are humid, so for several months a year your crawl space is being ventilated with very damp air, and humidity builds up over time. Fiberglass insulation is notorious for soaking up that water vapor. The fibers separate and take on a stringy, rope-like look, and pieces can get heavy enough to fall from between the joists. If you see insulation lying on the ground throughout the crawl space, this is the likely culprit.
Water can also get in from groundwater or a leaking pipe. If the problem is in just one area or corner, that may be the cause. A thorough inspection is often needed to pin it down.
Wet insulation needs to be replaced. Once fiberglass is saturated it loses its insulating value. If it's still up between the joists, it's doing more harm than good, holding water against the wood structure of your home.
2. Moldy insulation
Wet insulation holds water against the floor joists, which can lead to mold growing on the wood. The paper backing on fiberglass batts is also a common place for mold to grow when there's too much moisture.
- During mold remediation, porous materials like insulation should always be removed and thrown away.
- Structural materials like wood framing and concrete should be cleaned and left in place, as long as they're structurally sound.
- We strongly discourage mold treatments that only mist or fog the area and leave moldy insulation in your home.
Learn more about our crawl space mold remediation and insulation removal.
3. Pest waste
Another common reason to replace insulation is pest activity. Homes that have had rodents may have insulation holding urine or droppings. Depending on how bad it is, you may smell it in the house or at the crawl space entrance.
If you remove pest-soiled insulation yourself, wear proper protective gear. We strongly recommend a full-face respirator and coveralls, since droppings can fall into your face, eyes, ears, nose or mouth. The tight space makes the job harder, too.
4. Poor efficiency
If your insulation isn't damaged but you're still fighting high energy bills, the way your crawl space is ventilated and insulated may need to change.
Vented crawl spaces are designed to bring outdoor air under the house. Warm air rises and cool air sinks, so air moves up into the home and out through the attic eaves. This is called the stack effect, or chimney effect. Insulation between the floor joists gets in the way of that airflow, which can leave air stagnant under the house and let moisture build up in humid months.
The alternative is to seal the foundation and install a dehumidifier:
- The foundation walls are insulated, and the space between the floor joists is left open.
- The crawl space dehumidifier and your home's HVAC work together to clean, dry and condition the air in both the house and the crawl space.
- Air moves more freely between the two, and temperature and humidity are controlled in both.
This is called crawl space encapsulation. Not sure what your crawl space needs? Book a free inspection.