Basically, they are typically dark, dirty, damp, cramped, and littered with bugs, critters, plumbing and gas pipes, trash, debris and maybe insulation that has fallen or been pulled down by the afore-mentioned critters looking for a warm spot to nest. And all that fun stuff is right below the floor of your warm, dry, and clean home!
The unpleasant environment of the crawlspace (the region between the ground and your floor) can have a detrimental impact on the pleasant environment you want inside your home. There are some factors you can control, while others are things you pretty much must learn to tolerate. For instance, the crawlspace will probably always be dark, cramped and filled with plumbing and gas lines. But the dirt, dampness, bugs, critters, and deteriorated insulation can be improved or managed. And as far as how the crawlspace affects your home, there is one major rule – the crawlspace must either be inside the home or outside the home. That means it must be part of the living space (think basement, but short) or disconnected from the house thermally and atmospherically (keep the damp air and bugs down there).
Inside the home crawlspace – this means the environmental envelop of the house must extend down to include the crawlspace, by moving the insulated walls to the exterior walls of the crawlspace, and installing vapor retarding material over the dirt floor, while cutting off all ventilation to the exterior.
Outside the home crawlspace – this scenario calls for wide open ventilation to the outside air, the same vapor retarder to control moisture transport from the ground, and sealing every crack and crevice to keep air, moisture and bugs from traveling up into your home. Insulating the floor frame assembly is generally required, but there are specific ways to do so and materials selection is critical. Given the technical knowledge and expertise required, and the difficult working conditions (refer to the first sentence of this article), this type of work is best referred to professionals.