Crawlspaces are where people most often discover a need for a mold remediator. Usually in the process of trying to sell or buy a property the home inspection discovers mold in the crawlspace. Most crawlspaces have mold to some degree. The question to be asked is – is the mold observed consistent with the age of the house? Obviously a newly constructed property should not have significant mold but one would expect to find mold in older crawlspaces.
Crawlspaces should actually be thought of as exterior spaces but conditions in the crawlspace could have an impact on the air quality of the living space above. To determine if conditions in a crawlspace are impacting the living space would require collecting air and surface samples for analysis. A normal air sample collected in the living space of a house should look similar to an outside air sample in terms of types of mold observed. An air sample from a crawlspace would have different types of mold present than found in outside air. If air is moving from the crawlspace into the living space then mold types from the crawlspace would show up in the living space air sample.
Before a crawlspace remediation project is started the cause should be investigated. The mold is a symptom of a moisture problem so it could be as simple as needing to upgrade the vapor barrier. Containment for a crawlspace is generally simpler to set up and involves blocking the crawlspace vents and placing a HEPA filtered air filtration device to blow air out of the crawlspace and negatively pressurize it relative to the living space above and the outside air. Remediating a crawlspace may not necessarily require removing the subfloor insulation. In crawlspaces that have high moisture/humidity levels then you tend to find that the insulation is drooping and hanging. In this situation the insulation is no longer doing its designed job and should be replaced. In crawlspace where the insulation is still in reasonable condition the decision to keep or replace the insulation is generally a financial one. Obviously if insulation remains in place then the conditions above the insulation on the actual subfloor cannot be determined. Removing the insulation allows a full evaluation of the entire crawlspace. If it is known that mold from the crawlspace is moving to the living space, or the occupants of the living space have significant health issues, then I would recommend removing the insulation in those situations.
Crawlspace mold remediation projects are time consuming and labor intensive due to the cramped nature of the space and the amount of pipes, wiring and ducts, etc that have to be avoided.