It's extremely important to insulate a crawlspace. A crawlspace without insulation impacts energy bills and comfort levels. A properly insulated crawlspace will reflect heat back inside, rather than letting it escape and increase energy costs. Traditional fiberglass insulation is vulnerable to moisture and mold, and insulation usually becomes sodden and "drips" from the ceiling. This is why fiberglass is no longer used by most contractors. Most reputable crawlspace repair companies will recommend not only insulating the area with suitable products, but installing an encapsulation system to ensure the space remains sanitary, dry, and healthy.