The musty smell upstairs and the floors you can’t keep warm usually start in the crawl space under your home. Colorado’s dry air hides it: the moisture isn’t in your living room, it’s in the soil under the house, and the wide day-to-night temperature swings push it up through open foundation vents and into the rooms where you live. A crawl space encapsulation shuts that cycle down. The system seals the floor and walls under a heavy liner, locks the seams against moisture, and closes the vents so the space stops feeding damp air into your home.

Liftech is a certified SafeBasements dealer serving homeowners across Colorado, from the Denver metro through the Front Range. We install full encapsulation systems built for the dry-climate humidity swings that drive moisture into crawl spaces across the state.

A vapor barrier is a single sheet of plastic laid over the dirt floor. It slows the water vapor the bare ground gives off, but it leaves the foundation walls bare, the seams open, and the vents pulling outside air through the space. A crawl space encapsulation seals the whole area. A heavy liner covers the floor and runs up the foundation walls, every seam is taped, and the top edge is sealed tight to the wall so nothing tracks behind it. The foundation vents are closed permanently. Code once required those vents on the theory that outside air would dry the space out. It does the opposite, and modern building practice seals the crawl space.

Liftech insulates the foundation walls and the rim joists, the band of framing where the floor meets the foundation and outside air works its way in. Putting the insulation at the walls brings the crawl space inside the heated envelope of the house, so it stops swinging with the outdoor temperature and holds close to the conditions of the rooms above it. The air your floors draw from is dry and stable.

Beneath the liner sits a drainage layer. If water ever reaches the space, from a plumbing leak or groundwater after a heavy storm, it has a path to a low point instead of pooling against the barrier. Sealed at the floor and walls, insulated at its edges, and drained underneath, the crawl space holds a dry, conditioned climate the rest of the house can rely on.

On the sloped lots common around Denver and Boulder, builders often chose a crawl space over a full basement, and that vented, dirt-floored design still sits under older homes across the Front Range. Colorado’s climate may seem too dry to cause a moisture problem, with Denver seeing only around 15 inches of precipitation a year. But the ground under those homes is expansive clay, which holds water instead of letting it drain, so the soil stays a moisture source long after the surface looks dry.

Colorado’s wide day-to-night temperature swings draw that moisture up off the soil and into the crawl space. The foundation vents were cut to carry it away. Instead they pull in humid air through the summer and cold air through the winter, and the stack effect lifts all of it up through the floor into the rooms you use. The damp settles into the joists and subfloor, softens the wood, feeds mold, and brings in pests. It runs out of sight under the floor, so the musty smell or the cold floor upstairs is usually the first sign anyone notices.

Because the trouble sits under the floor, it usually shows up first in the rooms above it. These are the signs worth paying attention to:

• A musty smell that won’t clear. Damp air from the crawl space rises into the house and carries the smell of mold and wet wood with it. If a room smells earthy no matter how often you air it out, the source is often below the floor.
• Floors that stay cold. When the crawl space runs cold and damp, the floor above it does too, and no amount of heat seems to fix the room over it.
• Condensation on ducts, pipes, or the foundation walls. Beads of water on hard surfaces down there mean the air is holding more moisture than the space can handle.
• Mold or soft wood on the joists. Dark growth or wood that gives under a screwdriver on the framing overhead means moisture has been working on the structure for a while.
• Indoor humidity and allergies that flare in the house. Mold spores and dust mites build up in a damp crawl space and circulate upstairs through the air the floor draws in.
• Pests getting in through the crawl space. Rodents and insects move toward damp, sheltered ground and use the same gaps to reach the rest of the house.
• Heating and cooling bills that keep climbing. An open crawl space pulls outside air into the house year round, and the furnace and AC run longer to keep up.

Any one of these is worth a look. Several together usually means moisture has had time to settle in, and the longer the space stays open, the further it works into the wood and the air. A free crawl space inspection will tell you what’s driving it and whether encapsulation is the right fix.

Once the crawl space sits inside the home’s insulated envelope, the furnace and AC stop fighting the outside air that used to pour through the vents. The Department of Energy has found that conditioned crawl spaces use roughly 15 to 18 percent less heating and cooling energy than vented ones, and the first place you notice it is in floors that finally hold their warmth.

The air upstairs gets cleaner at the same time. Through the stack effect, much of what you breathe on the main floor rises out of the crawl space, so a damp one carries mold spores, dust mites, and musty air up into the house. Sealing and drying the space cuts that off, which usually shows up as less dust and fewer allergy flare-ups indoors.

Much of Colorado sits in a high-radon area, so radon is a fair question for any crawl space project. The liner helps: it works as a soil-gas retarder that slows radon from rising out of the ground, and it’s a standard layer in a radon-resistant setup. On its own, though, it is not a radon mitigation system. The EPA recommends testing every home, and if your reading comes back at or above 4.0 picocuries per liter, you need an active system that vents the gas outside. Test first, and treat encapsulation as one part of the answer.