How Crawl Space Encapsulation Improves Indoor Air

A lot of Kansas City homeowners tell us the same thing: the house smells a little musty, especially on the first floor, and nothing they clean seems to fix it. Nine times out of ten the source is under their feet. The crawl space is not a separate room. It is part of the air path of the house, and what lives down there ends up upstairs.

Why crawl space air reaches your living room

Warm air rises through a house and leaks out at the top, which pulls replacement air in at the bottom. That pull is called the stack effect, and in a home with a vented crawl space it draws air up through gaps around plumbing, ductwork, and the subfloor. Whatever is in that air comes along: damp, musty air, mold spores, dust, and even soil gases like radon. We see this most in older KC homes in Prairie Village, Overland Park, and Kansas City, MO, where the crawl space was never really sealed off.

What humid summers do to a vented crawl space

Vents were meant to let moisture out. In our humid Missouri and Kansas summers they mostly let it in. Warm, wet outdoor air hits the cooler surfaces down there, condenses, and leaves the wood framing and insulation damp. Once moisture stays high for a while, mold and musty odor follow, and the air you breathe upstairs carries them.

How encapsulation changes the air

Encapsulation closes the crawl space off from the outside. A heavy vapor barrier covers the floor and runs up the walls, seams are sealed, vents are closed off, and a dehumidifier or conditioned air keeps humidity in a healthy range. With the moisture source shut down, the damp smell fades, mold has less to feed on, and less outside air and soil gas gets pulled into the house. Our crawl space encapsulation page walks through each step, and the vapor barrier page covers the liner itself.

What you can expect, and what you cannot

Encapsulation is not an air purifier and it will not cure allergies. What it does is remove a big, constant source of damp air and spores from the house. Most people notice the musty smell drop off within days of the space being sealed and dried. If there is active mold on the framing, that gets cleaned or treated first so you are not sealing a problem in.

Frequently asked questions