Crawl Space Encapsulation & Insulation in Durham, NC

Crawl Space Encapsulation & Insulation is the work we get asked about most in Durham. Houses across the Triangle sit on brick or block foundations over a shallow crawl space, often with vents in the walls and fiberglass batts stapled or tucked between the floor joists. In theory the vents dry the space out. In a Durham summer, when the average dew point near the airport is close to 68F in July and August, those vents often bring in damp air that condenses on cooler surfaces underneath the house.

Signs the crawl space needs work

• A musty smell in the house, especially in summer.
• Insulation batts sagging, falling down or dark with moisture.
• Condensation dripping from ductwork or the underside of the floor.
• A torn, missing or partial plastic ground cover over red clay.
• Cold floors in January or high humidity indoors all summer.
• Standing water after heavy rain, which needs a drainage fix before anything else.

Two ways to fix it

Encapsulate. A heavy ground liner covers the floor and runs up the walls, seams are taped, vents and openings are sealed, and the foundation walls are insulated, usually with closed-cell foam. The crawl space then needs some way to stay dry, such as a dehumidifier or a small supply of conditioned air. ENERGY STAR's retrofit table for Zone 4A lists R-10 insulating sheathing or an R-13 batt for crawl space walls.

Insulate the floor and keep it vented. In some houses a sound vapor barrier on the ground and properly supported insulation under the floor does the job. ENERGY STAR lists R-19 for floors in Zone 4A. This route costs less up front but depends on the vents, the grading and the ground cover all doing their part.

What we check first

We look at grading and gutters outside, water lines inside, the moisture content of joists and sills, and signs of termites, since the state residential code rates termite risk in North Carolina as moderate to heavy. Where foam goes on foundation walls, we talk with you about keeping the top of the wall visible so a pest inspector can still see it. If the crawl space has standing water, drainage comes first; we will say so rather than sell you a liner that floods.

Crawl space insulation and your HVAC

Many Triangle houses have ductwork running through the crawl space. Once the space is sealed and dry, those ducts sit in a much milder environment, which cuts condensation on the duct jackets. We coordinate with your HVAC company if the plan includes conditioning the space or adding a dehumidifier. Get a free estimate