When the home was first built the crawl space was not considered part of the house.The crawl space environment is no different than that of a cave in the side of a mountain. It’s dark, dirty, and smelly and has small animals and bugs living in it. When the home was first built the crawl space was not considered part of the house. Excess building materials and waste was thrown down there because it was easier than picking it up and discarding it in the dumpster. I have personally taken out old refrigerator doors, tires, old pipes, a toilet with the seat and drop ceiling panels among other things. It is also not uncommon to remove the carcass of a dead animal or two. This is the condition before anyone tries to improve it. Back in the day it was required to have vents in the foundation to promote cross ventilation in order to help control the moisture that would escape from the ground. This caused a few other problems, cold air getting under the home and making the floors cold, allowing even more moisture to get in by way of the humid summer air and a constant supply of mold, mildew and fungus spores. The cold floors were addressed by installing fiberglass insulation in the floor joist cavity and the other two problems were thought to be unavoidable. Now we have a dark, dirty, smelly place that has small animals and bugs (powder post beetles, termites, creepy looking bugs about 1 ½ inches with long furry legs that run faster than my eleven year old son) living in it, we add more moisture via the vents and plenty of mildew, mold and fungus seeds. The next thing we do is add a fiberglass nesting material for the animals to bed in and then through the open vents in the foundation we make it cold enough in the winter to raise the heat bill and chase these small animals and bugs into the home in search of food and a warmer place to live.  By spring, a few mouse traps and a can of ant spray the home is ready to start this cycle over again. This is a reality for most crawl spaces so it is no wonder nobody wants to go down there.