The crawl space & the air you breathe.

Houses breathe from the bottom up. The technical term is the stack effect — warm air rises and pulls in replacement air from the lowest point in the building. In a Michigan house with a crawl space, that lowest point is dirt.

Forty to fifty percent of the air you breathe in your living room came from that crawl space first. If the crawl is damp — and most unencapsulated Michigan crawls are — the air in your house is too.

What that does over time: musty smell that won't go away, mold growing on rim joists, allergy symptoms that get worse in the spring, and eventually wood rot in floor framing.

Encapsulation is a 20-mil reinforced vapor barrier across the floor and up the walls, sealed crawl door, and a dehumidifier sized to the volume of the space. It runs $4,500 to $9,000 for a typical Michigan crawl. The before-and-after on indoor humidity is usually 65% down to 45%, which is the difference between a house that smells like a basement and one that doesn't.