Short answer: Crawl space insulation should be replaced or removed when it is wet, sagging, moldy, pest-damaged, blocking inspection, or no longer performing. After encapsulation, the insulation strategy may change because the crawl space is being treated as a controlled moisture zone instead of a vented, damp space.
For the full service path, see how Catawba handles crawl space encapsulation in Charlotte, NC, including inspection, moisture control, drainage, vapor barrier work, and humidity control.
Why old insulation can create problems
Fiberglass insulation can hold moisture and odor when the crawl space has been damp. It can sag away from the subfloor, hide wood conditions, collect debris, and make it harder to inspect joists, plumbing, and ducts.
If the insulation is wet or damaged, sealing the crawl space below it does not automatically make it healthy. The material may need to be removed so the framing can be inspected and the new moisture-control system can work cleanly.
How encapsulation changes the insulation decision
In a vented crawl space, insulation is often installed between floor joists because outdoor air is expected to pass through the space. In an encapsulated crawl space, the goal is different: control moisture, reduce air exchange, and make the area easier to maintain.
That can lead to a different insulation approach depending on the home, code requirements, HVAC location, duct conditions, and how the crawl space will be conditioned or dehumidified.
What should be documented before work starts
Before insulation is removed or replaced, the inspection should document moisture, odor, visible growth, wood staining, pest activity, duct condensation, and access needs. That gives the homeowner a reason for the recommendation.
The final scope should explain what insulation stays, what comes out, what gets replaced, and how the crawl space will be monitored after encapsulation.