Spray Foam Insulation in Durham, NC

Spray Foam Insulation is a liquid that expands on contact into a foam that fills gaps, sticks to wood and masonry, and cures in place. Unlike batts or loose fill, it blocks air movement as well as heat flow, so it handles both of the problems that make Durham houses uncomfortable: hot, humid air sneaking in during summer and warm air leaking out in winter. We spray two kinds of foam, and choosing between them is most of the skill.

Open-cell foam

Open-cell foam is light and soft, with cells that are not fully closed. It expands far beyond its sprayed thickness, which makes it good at filling irregular framing, and it damps sound. HomeGuide's 2026 guide lists it at about R-3.5 to R-3.7 per inch and $1.50 to $3.50 per square foot installed. Because it lets some water vapor through, it works best above grade: on the underside of a roof deck to bring the attic inside the conditioned space, in bonus room walls and kneewalls, and in interior walls where noise matters.

Closed-cell foam

Closed-cell foam is dense and hard. It runs about R-5 to R-7 per inch and $3.00 to $5.00 per square foot in the same guide. At typical thickness it slows vapor, adds stiffness and does not soak up water. That makes it our usual choice where moisture is the enemy: crawl space foundation walls, rim joists, and slab edges, plus metal buildings and garage doors where condensation forms. It costs more per inch, so we use it where those properties matter.

Where foam makes sense in a Triangle house

• Under the roof deck. If the air handler and ducts live in the attic, which is common in Triangle houses built since the 1970s, spraying the roof deck pulls them inside the insulated space instead of leaving them in a 130-degree attic.
• Crawl space walls and rim joists. Closed-cell foam on the walls of a sealed crawl space keeps the floor above warmer in winter and stops humid air from creeping in at the band joist.
• Bonus rooms and kneewalls. The odd shapes of a room over the garage are hard to insulate with batts and easy to fill with foam.
• Older walls opened up. When plaster or drywall is off in an older Durham house, open cavities can be sprayed before the walls close again.

Where it does not

On a wide, flat attic floor with easy access, foam is rarely the cheapest way to reach R-38 or more. Sealing the bypasses with foam and caulk and then blowing loose fill to depth usually costs less. We will tell you when that is the better plan.

Before we spray

Foam goes onto clean, dry surfaces only. We check for roof leaks, wet framing, active termite damage and wiring that needs attention first. Exposed foam in living spaces and some attics needs a thermal or ignition barrier under building code, and we explain what your space needs before you approve the work. You will need to stay out of the house while foam is sprayed and for a period afterward; HomeGuide's guidance is at least 24 hours. Get a free estimate